#define _POSIX_C_SOURCE 200809L
#include "store.h"
#include "state.h"
#include <assert.h>
#include <dirent.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <pthread.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#define CHECK(x) do { if (!(x)) { fprintf(stderr, "%s:%d: %s\n", __FILE__, __LINE__, #x); abort(); } } while (0)

static int fail_stage = -1;
static int crash;
static int slow_once; /* the next publication pauses before its data sync */
static int held_sync;  /* 1: the next publication waits after its head write; 2: it is waiting */
static void pause_ms(long ms) {
    struct timespec wait = {ms / 1000, (ms % 1000) * 1000000};
    nanosleep(&wait, NULL);
}
int pure_store_test_fault(PureStoreStage stage) {
    if (stage == PURE_BEFORE_FILE_SYNC && __atomic_exchange_n(&slow_once, 0, __ATOMIC_SEQ_CST)) pause_ms(100);
    int one = 1;
    if (stage == PURE_BEFORE_DIR_SYNC &&
        __atomic_compare_exchange_n(&held_sync, &one, 2, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
        while (__atomic_load_n(&held_sync, __ATOMIC_SEQ_CST) == 2) pause_ms(1);
    if ((int)stage != fail_stage) return 0;
    if (crash) _exit(77);
    return 1;
}
bool pure_tree_test_shape(const char *path, const char *key, unsigned *height,
                          uint64_t *leaves, uint64_t *small, uint64_t *file_end);

void pure_draft_test_arena(const PureDraft *draft, size_t *nodes, size_t *bytes);
unsigned long pure_tree_test_publications(void);
unsigned long pure_tree_test_syncs(void);
void pure_tree_test_forget(void);

/* The file: head slots in blocks 0 and 1 (sequence at +8, end at +16,
 * catalog at +24), commits from DATA_START, each a 128-byte record (its head)
 * and then its bytes. */
enum { KEYS = 4, CAPACITY = 1 << 20, SLOT_BLOCK = 4096, DATA_START = 8192, RECORD_SIZE = 128 };
typedef struct { unsigned char *bytes; size_t size; int64_t revision; } Oracle;

static uint32_t random_value(uint32_t *state) {
    *state ^= *state << 13;
    *state ^= *state >> 17;
    *state ^= *state << 5;
    return *state;
}

static void expect(const char *path, const char *key, const Oracle *o) {
    PureStoredView view;
    CHECK(pure_store_get(path, key, PURE_OBJECT_LIMIT, &view) == PURE_OK);
    CHECK(view.revision == o->revision && view.body.size == o->size);
    CHECK(!o->size || !memcmp(view.body.data, o->bytes, o->size));
    pure_store_release(&view);
}

static uint64_t file_size(const char *path) {
    char name[512];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    struct stat info;
    CHECK(stat(name, &info) == 0);
    return (uint64_t)info.st_size;
}

/* Where the newest commit ends. */
static uint64_t published_end(const char *path, const char *key) {
    unsigned height;
    uint64_t leaves, small, end;
    CHECK(pure_tree_test_shape(path, key, &height, &leaves, &small, &end));
    return end;
}

static uint64_t field_at(int fd, uint64_t at) {
    unsigned char bytes[8];
    CHECK(pread(fd, bytes, 8, (off_t)at) == 8);
    uint64_t value = 0;
    for (unsigned i = 0; i < 8; ++i) value |= (uint64_t)bytes[i] << (8 * i);
    return value;
}

static uint64_t slot_field(int fd, unsigned slot, unsigned offset) { return field_at(fd, slot * SLOT_BLOCK + offset); }

/* Where the newest head is: the newer slot's, or the last record after it. */
static uint64_t newest_head(int fd) {
    uint64_t at = slot_field(fd, 0, 8) > slot_field(fd, 1, 8) ? 0 : SLOT_BLOCK;
    for (;;) {
        uint64_t end = field_at(fd, at + 16);
        unsigned char magic[8];
        if (pread(fd, magic, 8, (off_t)end) != 8 || memcmp(magic, "PUREREC1", 8) ||
            field_at(fd, end + 8) != field_at(fd, at + 8) + 1) return at;
        at = end;
    }
}

static void fill(unsigned char *bytes, size_t size, uint32_t *state) {
    for (size_t i = 0; i < size; ++i) bytes[i] = (unsigned char)random_value(state);
}

/* Random edits against a flat oracle, including views held across later
 * commits and compactions. Every stored node must stay balanced. */
static void oracle(const char *path) {
    static const char *keys[KEYS] = {"alpha", "b", "gamma-long_key-0123456789", "z"};
    Oracle docs[KEYS] = {{0}};
    unsigned char *insert = malloc(65536);
    for (unsigned k = 0; k < KEYS; ++k) CHECK((docs[k].bytes = malloc(CAPACITY)));
    CHECK(insert);
    uint32_t state = 0x9e3779b9u;
    PureStoredView held = {0};
    unsigned char *held_copy = malloc(CAPACITY);
    size_t held_size = 0;
    unsigned max_height = 0;
    size_t max_size = 0, splices = 0;
    for (unsigned step = 0; step < 6000; ++step) {
        unsigned k = random_value(&state) % KEYS;
        Oracle *o = &docs[k];
        uint32_t kind = random_value(&state) % 100;
        size_t count = kind < 70 ? random_value(&state) % 24 :
                       kind < 95 ? random_value(&state) % 6000 : random_value(&state) % 65536;
        int64_t revision;
        fill(insert, count, &state);
        if (kind >= 98 || !o->revision) {
            CHECK(pure_store_put(path, keys[k], o->revision, (PureSpan){insert, count}, &revision) == PURE_OK);
            memcpy(o->bytes, insert, count);
            o->size = count;
        } else {
            size_t offset = o->size ? random_value(&state) % (o->size + 1) : 0;
            size_t remove = o->size - offset ? random_value(&state) % (o->size - offset + 1) : 0;
            if (random_value(&state) % 24) remove = remove % 64;
            if (o->size - remove + count > CAPACITY) { count = 0; remove = o->size - offset; }
            CHECK(pure_store_splice(path, keys[k], o->revision, offset, remove,
                                    (PureSpan){insert, count}, PURE_OBJECT_LIMIT, &revision) == PURE_OK);
            memmove(o->bytes + offset + count, o->bytes + offset + remove, o->size - offset - remove);
            memcpy(o->bytes + offset, insert, count);
            o->size = o->size - remove + count;
            ++splices;
        }
        if (o->size > max_size) max_size = o->size;
        CHECK(revision == o->revision + 1);
        o->revision = revision;
        expect(path, keys[k], o);
        unsigned height;
        uint64_t leaves, small, end;
        CHECK(pure_tree_test_shape(path, keys[k], &height, &leaves, &small, &end));
        CHECK(small == 0);
        if (height > max_height) max_height = height;
        if (step % 97 == 0) {
            if (held.mapped_size) {
                CHECK(held.body.size == held_size && !memcmp(held.body.data, held_copy, held_size));
                pure_store_release(&held);
            }
            CHECK(pure_store_get(path, keys[k], PURE_OBJECT_LIMIT, &held) == PURE_OK);
            held_size = held.body.size;
            if (held_size) memcpy(held_copy, held.body.data, held_size);
        }
    }
    if (held.mapped_size) {
        CHECK(held.body.size == held_size && !memcmp(held.body.data, held_copy, held_size));
        pure_store_release(&held);
    }
    for (unsigned k = 0; k < KEYS; ++k) { expect(path, keys[k], &docs[k]); free(docs[k].bytes); }
    CHECK(max_height >= 2 && max_height <= 4 && max_size > 262144);
    printf("{\"oracle_steps\":6000,\"splices\":%zu,\"max_document_bytes\":%zu,\"max_height\":%u}\n",
           splices, max_size, max_height);
    free(insert);
    free(held_copy);
}

/* A one-byte insert, delete or replacement in a 1 MiB document appends only
 * its changed leaf and path, not another copy of the document. */
static void amplification(const char *path) {
    size_t size = 1048576;
    unsigned char *bytes = malloc(size + 1);
    uint32_t state = 7;
    CHECK(bytes);
    fill(bytes, size, &state);
    int64_t revision;
    CHECK(pure_store_put(path, "large", 0, (PureSpan){bytes, size}, &revision) == PURE_OK);
    Oracle o = {bytes, size, revision};
    unsigned char byte = 'Q';
    const size_t edits[][3] = {{size / 2, 0, 1}, {size / 3, 1, 0}, {size - 1, 1, 1}, {0, 0, 1}};
    uint64_t worst = 0;
    for (size_t i = 0; i < sizeof(edits) / sizeof(*edits); ++i) {
        uint64_t before = published_end(path, "large");
        size_t offset = edits[i][0], remove = edits[i][1], count = edits[i][2];
        CHECK(pure_store_splice(path, "large", o.revision, offset, remove, (PureSpan){&byte, count},
                                PURE_OBJECT_LIMIT, &revision) == PURE_OK);
        memmove(bytes + offset + count, bytes + offset + remove, o.size - offset - remove);
        memcpy(bytes + offset, &byte, count);
        o.size = o.size - remove + count;
        o.revision = revision;
        uint64_t after = published_end(path, "large");
        if (after > before && after - before > worst) worst = after - before;
        expect(path, "large", &o);
    }
    /* Compaction may shrink the file; growth per edit is the claim. */
    CHECK(worst > 0 && worst < 16384);
    unsigned height;
    uint64_t leaves, small, end;
    CHECK(pure_tree_test_shape(path, "large", &height, &leaves, &small, &end));
    CHECK(small == 0 && height == 2 && leaves >= 256 && leaves <= 512);
    printf("{\"one_byte_edit_max_appended_bytes\":%llu,\"height\":%u,\"leaves\":%llu}\n",
           (unsigned long long)worst, height, (unsigned long long)leaves);
    free(bytes);
}

static void faults(const char *path) {
    unsigned char text[] = "fault-free";
    int64_t revision;
    CHECK(pure_store_put(path, "fault", 0, (PureSpan){text, 10}, &revision) == PURE_OK);
    Oracle o = {text, 10, revision};
    uint64_t size = file_size(path), end = published_end(path, "fault");
    for (fail_stage = PURE_AFTER_HEADER; fail_stage <= PURE_BEFORE_RENAME; ++fail_stage) {
        CHECK(pure_store_splice(path, "fault", o.revision, 1, 3, (PureSpan){text, 5},
                                PURE_OBJECT_LIMIT, &revision) == PURE_STORE_ERROR);
        expect(path, "fault", &o);
        /* The bytes stayed unpublished, in the written zeros after the end. */
        CHECK(published_end(path, "fault") == end && file_size(path) == size);
    }
    fail_stage = PURE_BEFORE_DIR_SYNC;
    CHECK(pure_store_splice(path, "fault", o.revision, 10, 0, (PureSpan){text, 2},
                            PURE_OBJECT_LIMIT, &revision) == PURE_UNCERTAIN);
    fail_stage = -1;
    unsigned char next[] = "fault-freefa";
    o = (Oracle){next, 12, o.revision + 1};
    CHECK(revision == o.revision);
    expect(path, "fault", &o);
}

/* A process that dies at each publication stage leaves either the previous
 * or the next complete version; the next commit overwrites its unpublished
 * bytes. A head it wrote but did not sync is made durable before the next
 * writer builds on it. */
static void crashes(const char *path) {
    unsigned char text[] = "crash-base";
    int64_t revision;
    CHECK(pure_store_put(path, "crash", 0, (PureSpan){text, 10}, &revision) == PURE_OK);
    Oracle o = {text, 10, revision};
    for (int stage = PURE_AFTER_HEADER; stage <= PURE_BEFORE_DIR_SYNC; ++stage) {
        uint64_t before = published_end(path, "crash");
        pid_t child = fork();
        CHECK(child >= 0);
        if (!child) {
            crash = 1;
            fail_stage = stage;
            pure_store_splice(path, "crash", o.revision, 0, 1, (PureSpan){(const unsigned char *)"C", 1},
                              PURE_OBJECT_LIMIT, &revision);
            _exit(0);
        }
        int status;
        CHECK(waitpid(child, &status, 0) == child && WIFEXITED(status) && WEXITSTATUS(status) == 77);
        if (stage == PURE_BEFORE_DIR_SYNC) { text[0] = 'C'; ++o.revision; }
        expect(path, "crash", &o);
        uint64_t published = published_end(path, "crash");
        CHECK(stage == PURE_BEFORE_DIR_SYNC ? published > before : published == before);
        unsigned long syncs = pure_tree_test_syncs();
        CHECK(pure_store_splice(path, "crash", o.revision, 10, 0, (PureSpan){(const unsigned char *)"", 0},
                                PURE_OBJECT_LIMIT, &revision) == PURE_OK);
        o.revision = revision;
        expect(path, "crash", &o);
        CHECK(pure_tree_test_syncs() - syncs == (stage == PURE_BEFORE_DIR_SYNC ? 2u : 1u));
        CHECK(published_end(path, "crash") > published);
    }
}

static void tear(const char *path, uint64_t at) {
    char name[512];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    int fd = open(name, O_RDWR);
    unsigned char torn;
    CHECK(fd >= 0 && pread(fd, &torn, 1, (off_t)at) == 1);
    torn ^= 0x5a;
    CHECK(pwrite(fd, &torn, 1, (off_t)at) == 1 && close(fd) == 0);
}

/* A torn newest record exposes the previous commit to a new process, and the
 * next writer overwrites that record and the commit's bytes. A torn slot
 * costs only a longer walk: the other slot's head leads along the records. */
static void torn_head(const char *path) {
    unsigned char first[] = "first", second[] = "second";
    int64_t revision;
    CHECK(pure_store_put(path, "torn", 0, (PureSpan){first, 5}, &revision) == PURE_OK);
    Oracle o = {first, 5, revision};
    uint64_t record = published_end(path, "torn"); /* where the next commit's record goes */
    CHECK(pure_store_put(path, "torn", o.revision, (PureSpan){second, 6}, &revision) == PURE_OK);
    tear(path, SLOT_BLOCK + 20);
    pure_tree_test_forget();
    expect(path, "torn", &(Oracle){second, 6, revision});
    tear(path, record + 20);
    pure_tree_test_forget();
    expect(path, "torn", &o);
    CHECK(pure_store_put(path, "torn", o.revision + 1, (PureSpan){first, 1}, &revision) == PURE_CONFLICT);
    CHECK(pure_store_put(path, "torn", o.revision, (PureSpan){second, 3}, &revision) == PURE_OK);
    o = (Oracle){second, 3, revision};
    CHECK(published_end(path, "torn") < record + RECORD_SIZE + 4096); /* it went where the torn one was */
    pure_tree_test_forget();
    expect(path, "torn", &o);
}

/* Commits are found along their records: from a slot's head, which every
 * CHECKPOINT commits moves on, by a new process too; a damaged record ends
 * the walk at the commit before it, which the next writer builds on. */
static void records(const char *path) {
    int64_t revision;
    uint64_t ends[41];
    char text[16];
    CHECK(pure_store_put(path, "walk", 0, (PureSpan){(const unsigned char *)"0", 1}, &revision) == PURE_OK);
    for (unsigned i = 1; i <= 40; ++i) {
        ends[i] = published_end(path, "walk");
        snprintf(text, sizeof(text), "%u", i);
        CHECK(pure_store_put(path, "walk", revision, (PureSpan){(const unsigned char *)text, strlen(text)},
                             &revision) == PURE_OK);
    }
    char name[512];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    int fd = open(name, O_RDONLY);
    CHECK(fd >= 0);
    uint64_t newest_slot = slot_field(fd, 0, 8) > slot_field(fd, 1, 8) ? slot_field(fd, 0, 8) : slot_field(fd, 1, 8);
    CHECK(close(fd) == 0);
    /* 42 commits (the empty file's first): heads in slots at 17 and 33. */
    CHECK(newest_slot == 33);
    pure_tree_test_forget();
    expect(path, "walk", &(Oracle){(unsigned char *)"40", 2, 41});
    pid_t child = fork();
    CHECK(child >= 0);
    if (!child) {
        pure_tree_test_forget(); /* a process that never saw them */
        PureStoredView view;
        _exit(pure_store_get(path, "walk", 16, &view) == PURE_OK && view.body.size == 2 &&
              !memcmp(view.body.data, "40", 2) && view.revision == 41 ? 0 : 1);
    }
    int status;
    CHECK(waitpid(child, &status, 0) == child && WIFEXITED(status) && WEXITSTATUS(status) == 0);
    /* Commit 37 ("37", revision 38) has a damaged record: the walk ends at 36. */
    tear(path, ends[37] + 30);
    pure_tree_test_forget();
    expect(path, "walk", &(Oracle){(unsigned char *)"36", 2, 37});
    CHECK(pure_store_put(path, "walk", 37, (PureSpan){(const unsigned char *)"x", 1}, &revision) == PURE_OK);
    CHECK(revision == 38 && published_end(path, "walk") < ends[38]);
    pure_tree_test_forget();
    expect(path, "walk", &(Oracle){(unsigned char *)"x", 1, 38});
}

/* A reader's view stays byte-identical while another process commits and
 * compacts; readers take no lock. */
static void isolation(const char *path) {
    size_t size = 300000;
    unsigned char *bytes = malloc(size);
    uint32_t state = 99;
    CHECK(bytes);
    fill(bytes, size, &state);
    int64_t revision;
    CHECK(pure_store_put(path, "shared", 0, (PureSpan){bytes, size}, &revision) == PURE_OK);
    PureStoredView view;
    CHECK(pure_store_get(path, "shared", size, &view) == PURE_OK);
    uint64_t before = file_size(path);
    pid_t child = fork();
    CHECK(child >= 0);
    if (!child) {
        int64_t at = revision;
        unsigned char byte = 'x';
        for (unsigned i = 0; i < 400; ++i)
            if (pure_store_splice(path, "shared", at, (i * 7919u) % size, 1, (PureSpan){&byte, 1},
                                  PURE_OBJECT_LIMIT, &at) != PURE_OK) _exit(1);
        _exit(0);
    }
    int status;
    CHECK(waitpid(child, &status, 0) == child && WIFEXITED(status) && WEXITSTATUS(status) == 0);
    CHECK(view.revision == revision && view.body.size == size && !memcmp(view.body.data, bytes, size));
    pure_store_release(&view);
    PureStoredView latest;
    CHECK(pure_store_get(path, "shared", size, &latest) == PURE_OK && latest.revision == revision + 400);
    pure_store_release(&latest);
    /* About 2 MB of path copies without compaction would exceed this. */
    CHECK(file_size(path) < before + 3 * 524288);
    free(bytes);
}

/* Damaged branch bytes are reported as storage errors, never trusted. */
static void corruption(const char *path) {
    unsigned char *bytes = malloc(200000);
    uint32_t state = 3;
    CHECK(bytes);
    fill(bytes, 200000, &state);
    int64_t revision;
    CHECK(pure_store_put(path, "damaged", 0, (PureSpan){bytes, 200000}, &revision) == PURE_OK);
    char name[512];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    uint64_t end = published_end(path, "damaged");
    int fd = open(name, O_RDWR);
    CHECK(fd >= 0);
    unsigned errors = 0;
    for (unsigned i = 0; i < 3000; ++i) {
        off_t at = (off_t)(DATA_START + random_value(&state) % (end - DATA_START));
        unsigned char original, damaged;
        CHECK(pread(fd, &original, 1, at) == 1);
        damaged = original ^ (unsigned char)(1u << (random_value(&state) % 8));
        CHECK(pwrite(fd, &damaged, 1, at) == 1);
        PureStoredView view;
        PureResult result = pure_store_get(path, "damaged", PURE_OBJECT_LIMIT, &view);
        CHECK(result == PURE_OK || result == PURE_STORE_ERROR || result == PURE_NOT_FOUND);
        if (result == PURE_OK) pure_store_release(&view); else ++errors;
        CHECK(pwrite(fd, &original, 1, at) == 1);
    }
    CHECK(close(fd) == 0 && errors > 0);
    free(bytes);
}

static void many_keys(const char *path) {
    int64_t revision;
    char key[32];
    for (unsigned i = 0; i < 1024; ++i) {
        unsigned id = (i * 617u) % 1024u;
        snprintf(key, sizeof(key), "doc-%04u", id);
        CHECK(pure_store_put(path, key, 0, (PureSpan){(const unsigned char *)key, strlen(key)}, &revision) == PURE_OK);
    }
    for (unsigned id = 0; id < 1024; ++id) {
        snprintf(key, sizeof(key), "doc-%04u", id);
        Oracle o = {(unsigned char *)key, strlen(key), 1};
        expect(path, key, &o);
    }
    PureStoredView view;
    CHECK(pure_store_get(path, "doc-1024", 64, &view) == PURE_NOT_FOUND);
    CHECK(pure_store_get(path, "doc-0001", 3, &view) == PURE_BUDGET);
    CHECK(pure_store_splice(path, "doc-0002", 1, 9, 0, (PureSpan){0}, PURE_OBJECT_LIMIT, &revision) == PURE_LIMIT);
    CHECK(pure_store_put(path, "doc-0003", 0, (PureSpan){0}, &revision) == PURE_CONFLICT && revision == 1);
}

/* The newest catalog of a one-key store is one leaf; forge its revision. */
static void revision_limit(const char *path) {
    int64_t revision;
    CHECK(pure_store_put(path, "work", 0, (PureSpan){(const unsigned char *)"w", 1}, &revision) == PURE_OK);
    char name[512];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    int fd = open(name, O_RDWR);
    CHECK(fd >= 0);
    uint64_t catalog = field_at(fd, newest_head(fd) + 24);
    CHECK(catalog >> 63);
    const unsigned char maximum[] = {255,255,255,255,255,255,255,127};
    off_t record = (off_t)(catalog & ((UINT64_C(1) << 62) - 1));
    CHECK(pwrite(fd, maximum, 8, record + 80) == 8 && close(fd) == 0);
    /* The forged commit no longer matches its digest; this process wrote it
     * and does not read it again, a new process would pass over it. */
    PureStoredView view;
    CHECK(pure_store_get(path, "work", 1, &view) == PURE_OK && view.revision == INT64_MAX);
    pure_store_release(&view);
    CHECK(pure_store_splice(path, "work", INT64_MAX, 0, 0, (PureSpan){0}, PURE_OBJECT_LIMIT, &revision) == PURE_LIMIT);
}

static bool count_key(void *context, const char *key) {
    (void)key;
    ++*(unsigned *)context;
    return true;
}

static void keys(const char *path) {
    unsigned count = 0;
    CHECK(pure_store_keys(path, count_key, &count) == PURE_OK && count == 0);
    int64_t revision;
    const char *names[] = {"m", "a", "zz", "a-b", "A"};
    for (unsigned i = 0; i < 5; ++i)
        CHECK(pure_store_put(path, names[i], 0, (PureSpan){0}, &revision) == PURE_OK);
    CHECK(pure_store_keys(path, count_key, &count) == PURE_OK && count == 5);
}

typedef struct { unsigned char *out; size_t spans, largest, limit; } Gather;

static bool gather(void *context, PureSpan span) {
    Gather *g = context;
    memcpy(g->out, span.data, span.size);
    g->out += span.size;
    if (span.size > g->largest) g->largest = span.size;
    return ++g->spans != g->limit;
}

static void expect_draft(const PureDraft *draft, const Oracle *o, unsigned char *scratch) {
    Gather g = {scratch, 0, 0, 0};
    CHECK(pure_draft_size(draft) == o->size && pure_draft_revision(draft) == o->revision);
    CHECK(pure_draft_read(draft, 0, o->size, gather, &g) == PURE_OK);
    CHECK((size_t)(g.out - scratch) == o->size && (!o->size || !memcmp(scratch, o->bytes, o->size)));
    CHECK(g.largest <= 4096);
}

static void apply(Oracle *o, size_t offset, size_t remove, const unsigned char *insert, size_t count) {
    memmove(o->bytes + offset + count, o->bytes + offset + remove, o->size - offset - remove);
    if (count) memcpy(o->bytes + offset, insert, count);
    o->size = o->size - remove + count;
}

/* Edits live only in the draft until commit; each commit continues from the
 * published version with an empty arena. */
static void drafts(const char *path) {
    Oracle o = {malloc(CAPACITY), 0, 0};
    unsigned char *scratch = malloc(CAPACITY), *insert = malloc(65536);
    CHECK(o.bytes && scratch && insert);
    PureDraft *draft;
    PureStoredView view;
    CHECK(pure_draft_open(path, "draft", &draft) == PURE_OK);
    expect_draft(draft, &o, scratch);
    uint32_t state = 0x1234567u;
    for (unsigned step = 0; step < 20000; ++step) {
        uint32_t kind = random_value(&state) % 100;
        size_t count = kind < 80 ? random_value(&state) % 8 :
                       kind < 98 ? random_value(&state) % 4000 : random_value(&state) % 65536;
        size_t offset = o.size ? random_value(&state) % (o.size + 1) : 0;
        size_t remove = o.size - offset ? random_value(&state) % (o.size - offset + 1) : 0;
        if (random_value(&state) % 64) remove %= 16;
        if (o.size - remove + count > CAPACITY) count = 0;
        fill(insert, count, &state);
        CHECK(pure_draft_splice(draft, offset, remove, (PureSpan){insert, count}) == PURE_OK);
        apply(&o, offset, remove, insert, count);
        if (step % 97 == 0) expect_draft(draft, &o, scratch);
        if (step % 1000 == 999) {
            if (o.revision) CHECK(pure_store_get(path, "draft", PURE_OBJECT_LIMIT, &view) == PURE_OK &&
                                  view.revision == o.revision);
            if (o.revision) pure_store_release(&view);
            int64_t revision;
            CHECK(pure_draft_commit(draft, &revision) == PURE_OK && revision == o.revision + 1);
            o.revision = revision;
            expect(path, "draft", &o);
            expect_draft(draft, &o, scratch);
            size_t nodes, bytes;
            pure_draft_test_arena(draft, &nodes, &bytes);
            CHECK(nodes == 0);
        }
    }
    CHECK(o.size > 100000);
    Gather g = {scratch, 0, 0, 3};
    CHECK(pure_draft_read(draft, 0, o.size, gather, &g) == PURE_OK && g.spans == 3);
    CHECK(pure_draft_splice(draft, o.size + 1, 0, (PureSpan){0}) == PURE_LIMIT);
    CHECK(pure_draft_splice(draft, 0, o.size + 1, (PureSpan){0}) == PURE_LIMIT);
    CHECK(pure_draft_read(draft, o.size, 1, gather, &g) == PURE_LIMIT);
    expect_draft(draft, &o, scratch);
    pure_draft_close(draft);
    printf("{\"draft_steps\":20000,\"draft_commits\":%lld,\"draft_bytes\":%zu}\n",
           (long long)o.revision, o.size);
    free(o.bytes);
    free(scratch);
    free(insert);
}

/* Long typing and deleting at one place keeps only the live path in memory,
 * and its commit appends the typed bytes and path, not the document. */
static void typing(const char *path) {
    size_t size = 1048576;
    Oracle o = {malloc(size + 40000), size, 0};
    unsigned char *scratch = malloc(size + 40000);
    uint32_t state = 5;
    CHECK(o.bytes && scratch);
    fill(o.bytes, size, &state);
    CHECK(pure_store_put(path, "typed", 0, (PureSpan){o.bytes, size}, &o.revision) == PURE_OK);
    PureDraft *draft;
    CHECK(pure_draft_open(path, "typed", &draft) == PURE_OK);
    size_t cursor = size / 2, nodes, bytes, peak = 0;
    for (unsigned i = 0; i < 30000; ++i) {
        unsigned char byte = (unsigned char)('a' + i % 26);
        if (i % 3 == 2) {
            CHECK(pure_draft_splice(draft, cursor - 1, 1, (PureSpan){0}) == PURE_OK);
            apply(&o, --cursor, 1, NULL, 0);
        } else {
            CHECK(pure_draft_splice(draft, cursor, 0, (PureSpan){&byte, 1}) == PURE_OK);
            apply(&o, cursor++, 0, &byte, 1);
        }
        pure_draft_test_arena(draft, &nodes, &bytes);
        if (bytes > peak) peak = bytes;
    }
    expect_draft(draft, &o, scratch);
    /* Reachable: 10,000 net typed bytes, the leaves they landed in and one
     * path. Unreachable copies are reclaimed past max(reachable, 32 KiB). */
    CHECK(peak < 2 * (10000 + 4 * 4096 + 2048) + 32768 + 8192);
    uint64_t before = published_end(path, "typed");
    int64_t revision;
    CHECK(pure_draft_commit(draft, &revision) == PURE_OK);
    o.revision = revision;
    uint64_t appended = published_end(path, "typed") - before;
    CHECK(appended < 10000 + 16384);
    expect(path, "typed", &o);
    pure_draft_close(draft);
    printf("{\"typing_keystrokes\":30000,\"peak_arena_bytes\":%zu,\"commit_appended_bytes\":%llu}\n",
           peak, (unsigned long long)appended);
    free(o.bytes);
    free(scratch);
}

/* Two drafts of one key: the second commit conflicts and keeps its edits. */
static void draft_conflict(const char *path) {
    unsigned char scratch[64];
    int64_t revision;
    CHECK(pure_store_put(path, "shared", 0, (PureSpan){(const unsigned char *)"base", 4}, &revision) == PURE_OK);
    PureDraft *first, *second;
    CHECK(pure_draft_open(path, "shared", &first) == PURE_OK && pure_draft_open(path, "shared", &second) == PURE_OK);
    CHECK(pure_draft_splice(first, 4, 0, (PureSpan){(const unsigned char *)"-one", 4}) == PURE_OK);
    CHECK(pure_draft_splice(second, 0, 0, (PureSpan){(const unsigned char *)"two-", 4}) == PURE_OK);
    CHECK(pure_draft_commit(first, &revision) == PURE_OK && revision == 2);
    CHECK(pure_draft_commit(second, &revision) == PURE_CONFLICT && revision == 2);
    Oracle kept = {(unsigned char *)"two-base", 8, 1};
    expect_draft(second, &kept, scratch);
    Oracle stored = {(unsigned char *)"base-one", 8, 2};
    expect(path, "shared", &stored);
    pure_draft_close(second);
    CHECK(pure_draft_open(path, "shared", &second) == PURE_OK);
    expect_draft(second, &stored, scratch);
    CHECK(pure_store_put(path, "shared", 2, (PureSpan){(const unsigned char *)"x", 1}, &revision) == PURE_OK);
    CHECK(pure_draft_commit(first, &revision) == PURE_CONFLICT && revision == 3);
    pure_draft_close(first);
    pure_draft_close(second);
}

/* Another key's writes compact the file under an open draft; the draft's
 * stored extents are copied from its old mapping on commit. */
static void draft_relocation(const char *path) {
    unsigned char *big = malloc(300000), scratch[20000];
    uint32_t state = 11;
    CHECK(big);
    fill(big, 300000, &state);
    Oracle o = {malloc(20000), 12000, 0};
    CHECK(o.bytes);
    fill(o.bytes, o.size, &state);
    CHECK(pure_store_put(path, "kept", 0, (PureSpan){o.bytes, o.size}, &o.revision) == PURE_OK);
    PureDraft *draft;
    CHECK(pure_draft_open(path, "kept", &draft) == PURE_OK);
    CHECK(pure_draft_splice(draft, 6000, 10, (PureSpan){(const unsigned char *)"relocated", 9}) == PURE_OK);
    apply(&o, 6000, 10, (const unsigned char *)"relocated", 9);
    char name[512];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    struct stat before, after;
    CHECK(stat(name, &before) == 0);
    int64_t revision = 0;
    for (unsigned i = 0; i < 8; ++i)
        CHECK(pure_store_put(path, "other", revision, (PureSpan){big, 300000 - i}, &revision) == PURE_OK);
    CHECK(stat(name, &after) == 0 && after.st_ino != before.st_ino);
    CHECK(pure_draft_commit(draft, &revision) == PURE_OK && revision == o.revision + 1);
    o.revision = revision;
    expect(path, "kept", &o);
    expect_draft(draft, &o, scratch);
    Oracle other = {big, 300000 - 7, 8};
    expect(path, "other", &other);
    pure_draft_close(draft);
    free(o.bytes);
    free(big);
}

/* A held draft keeps earlier versions readable across later edits. */
static void draft_versions(const char *path) {
    static unsigned char bytes[200000], scratch[200000];
    uint32_t state = 17;
    fill(bytes, sizeof(bytes), &state);
    int64_t revision;
    CHECK(pure_store_put(path, "versioned", 0, (PureSpan){bytes, sizeof(bytes)}, &revision) == PURE_OK);
    PureDraft *draft;
    CHECK(pure_draft_open(path, "versioned", &draft) == PURE_OK);
    pure_draft_hold(draft, true);
    PureVersion first = pure_draft_version(draft);
    for (unsigned i = 0; i < 400; ++i) {
        unsigned char byte = (unsigned char)i;
        CHECK(pure_draft_splice(draft, (i * 977u) % 150000, 3, (PureSpan){&byte, 1}) == PURE_OK);
    }
    Gather g = {scratch, 0, 0, 0};
    CHECK(pure_draft_read_version(draft, first, 0, sizeof(bytes), gather, &g) == PURE_OK);
    CHECK((size_t)(g.out - scratch) == sizeof(bytes) && !memcmp(scratch, bytes, sizeof(bytes)));
    CHECK(pure_draft_size(draft) == sizeof(bytes) - 800);
    size_t nodes, held_bytes, after;
    pure_draft_test_arena(draft, &nodes, &held_bytes);
    pure_draft_hold(draft, false);
    pure_draft_test_arena(draft, &nodes, &after);
    CHECK(after < held_bytes);
    pure_draft_close(draft);
}

/* A draft without a store: edits, versions, restore and reclamation. */
static void anonymous_draft(const char *path) {
    (void)path;
    Oracle o = {malloc(CAPACITY), 0, 0};
    unsigned char *scratch = malloc(CAPACITY), insert[3000];
    PureDraft *draft = pure_draft_new();
    CHECK(draft && o.bytes && scratch && pure_draft_size(draft) == 0 && pure_draft_revision(draft) == 0);
    uint32_t state = 42;
    for (unsigned step = 0; step < 4000; ++step) {
        size_t count = random_value(&state) % (step % 50 ? 12 : sizeof(insert));
        size_t offset = o.size ? random_value(&state) % (o.size + 1) : 0;
        size_t remove = o.size - offset ? random_value(&state) % (o.size - offset + 1) % 32 : 0;
        fill(insert, count, &state);
        bool abandon = random_value(&state) % 5 == 0;
        pure_draft_hold(draft, true);
        PureVersion before = pure_draft_version(draft);
        CHECK(pure_draft_splice(draft, offset, remove, (PureSpan){insert, count}) == PURE_OK);
        if (abandon) pure_draft_restore(draft, before);
        else apply(&o, offset, remove, insert, count);
        pure_draft_hold(draft, false);
        if (step % 37 == 0) expect_draft(draft, &o, scratch);
    }
    expect_draft(draft, &o, scratch);
    int64_t revision;
    CHECK(pure_draft_commit(draft, &revision) == PURE_INVALID);
    size_t nodes, bytes;
    pure_draft_test_arena(draft, &nodes, &bytes);
    CHECK(bytes < 2 * o.size + 65536);
    pure_draft_close(draft);
    free(o.bytes);
    free(scratch);
}

/* A failed commit changes neither the store nor the draft. */
static void draft_faults(const char *path) {
    unsigned char scratch[64];
    int64_t revision;
    CHECK(pure_store_put(path, "faulty", 0, (PureSpan){(const unsigned char *)"stable", 6}, &revision) == PURE_OK);
    PureDraft *draft;
    CHECK(pure_draft_open(path, "faulty", &draft) == PURE_OK);
    CHECK(pure_draft_splice(draft, 6, 0, (PureSpan){(const unsigned char *)"+edit", 5}) == PURE_OK);
    Oracle stored = {(unsigned char *)"stable", 6, 1}, edited = {(unsigned char *)"stable+edit", 11, 1};
    uint64_t size = file_size(path);
    for (fail_stage = PURE_AFTER_HEADER; fail_stage <= PURE_BEFORE_RENAME; ++fail_stage) {
        CHECK(pure_draft_commit(draft, &revision) == PURE_STORE_ERROR);
        expect(path, "faulty", &stored);
        expect_draft(draft, &edited, scratch);
        CHECK(file_size(path) == size);
    }
    fail_stage = PURE_BEFORE_DIR_SYNC;
    CHECK(pure_draft_commit(draft, &revision) == PURE_UNCERTAIN && revision == 2);
    fail_stage = -1;
    expect_draft(draft, &edited, scratch);
    CHECK(pure_draft_commit(draft, &revision) == PURE_CONFLICT && revision == 2);
    pure_draft_close(draft);
    CHECK(pure_draft_open(path, "faulty", &draft) == PURE_OK);
    edited.revision = 2;
    expect_draft(draft, &edited, scratch);
    CHECK(pure_draft_splice(draft, 0, 6, (PureSpan){0}) == PURE_OK);
    CHECK(pure_draft_commit(draft, &revision) == PURE_OK && revision == 3);
    Oracle final = {(unsigned char *)"+edit", 5, 3};
    expect(path, "faulty", &final);
    pure_draft_close(draft);
    CHECK(pure_draft_open(path, "bad/key", &draft) == PURE_INVALID && !draft);
}

static bool list_key(void *context, const char *key) {
    char *seen = context;
    strcat(seen, key);
    strcat(seen, ",");
    return true;
}

/* Several drafts publish in one commit: all or none, under process crashes,
 * faults and a stale draft. Runtime values stay out of the document keys. */
static void batch(const char *path) {
    unsigned char scratch[64];
    int64_t revision, revisions[3];
    CHECK(pure_store_put(path, "alpha", 0, (PureSpan){(const unsigned char *)"a0", 2}, &revision) == PURE_OK);
    CHECK(pure_store_put(path, "beta", 0, (PureSpan){(const unsigned char *)"b0", 2}, &revision) == PURE_OK);
    PureDraft *drafts[3];
    CHECK(pure_draft_open(path, "alpha", &drafts[0]) == PURE_OK && pure_draft_open(path, "beta", &drafts[1]) == PURE_OK);
    CHECK(pure_state_open(path, "values", &drafts[2]) == PURE_OK && pure_draft_revision(drafts[2]) == 0);
    PureDraft *bad;
    CHECK(pure_state_open(path, "bad.name", &bad) == PURE_INVALID && !bad);
    CHECK(pure_draft_splice(drafts[0], 2, 0, (PureSpan){(const unsigned char *)"+1", 2}) == PURE_OK);
    CHECK(pure_draft_splice(drafts[1], 0, 2, (PureSpan){(const unsigned char *)"B", 1}) == PURE_OK);
    CHECK(pure_draft_splice(drafts[2], 0, 0, (PureSpan){(const unsigned char *)"state", 5}) == PURE_OK);
    Oracle alpha = {(unsigned char *)"a0", 2, 1}, beta = {(unsigned char *)"b0", 2, 1};
    Oracle alpha_new = {(unsigned char *)"a0+1", 4, 1}, beta_new = {(unsigned char *)"B", 1, 1};
    Oracle state_new = {(unsigned char *)"state", 5, 0};
    /* A process that dies anywhere in the commit leaves all three as before,
     * or all three published once the head is written. */
    for (int stage = PURE_AFTER_HEADER; stage <= PURE_BEFORE_DIR_SYNC; ++stage) {
        pid_t child = fork();
        CHECK(child >= 0);
        if (!child) {
            crash = 1;
            fail_stage = stage;
            pure_draft_commit_all(drafts, 3, revisions);
            _exit(0);
        }
        int status;
        CHECK(waitpid(child, &status, 0) == child && WIFEXITED(status) && WEXITSTATUS(status) == 77);
        PureDraft *state;
        CHECK(pure_state_open(path, "values", &state) == PURE_OK);
        if (stage < PURE_BEFORE_DIR_SYNC) {
            expect(path, "alpha", &alpha);
            expect(path, "beta", &beta);
            CHECK(pure_draft_revision(state) == 0 && pure_draft_size(state) == 0);
            pure_draft_close(state);
            continue;
        }
        Oracle a = alpha_new, b = beta_new, v = state_new;
        a.revision = b.revision = 2;
        v.revision = 1;
        expect(path, "alpha", &a);
        expect(path, "beta", &b);
        expect_draft(state, &v, scratch);
        pure_draft_close(state);
        /* Undo the crashed commit's effect for the next checks. */
        CHECK(pure_store_put(path, "alpha", 2, (PureSpan){(const unsigned char *)"a0", 2}, &revision) == PURE_OK);
    }
    /* The same batch in this process is now stale on every key. */
    CHECK(pure_draft_commit_all(drafts, 3, revisions) == PURE_CONFLICT && revisions[0] == 3);
    for (unsigned i = 0; i < 3; ++i) pure_draft_close(drafts[i]);
    CHECK(pure_draft_open(path, "alpha", &drafts[0]) == PURE_OK && pure_draft_open(path, "beta", &drafts[1]) == PURE_OK);
    CHECK(pure_state_open(path, "values", &drafts[2]) == PURE_OK);
    CHECK(pure_draft_splice(drafts[0], 0, 2, (PureSpan){(const unsigned char *)"A", 1}) == PURE_OK);
    CHECK(pure_draft_splice(drafts[1], 1, 0, (PureSpan){(const unsigned char *)"!", 1}) == PURE_OK);
    CHECK(pure_draft_splice(drafts[2], 5, 0, (PureSpan){(const unsigned char *)"+", 1}) == PURE_OK);
    alpha = (Oracle){(unsigned char *)"a0", 2, 3};
    beta = (Oracle){(unsigned char *)"B", 1, 2};
    uint64_t size = file_size(path);
    for (fail_stage = PURE_AFTER_HEADER; fail_stage <= PURE_BEFORE_RENAME; ++fail_stage) {
        CHECK(pure_draft_commit_all(drafts, 3, revisions) == PURE_STORE_ERROR);
        expect(path, "alpha", &alpha);
        expect(path, "beta", &beta);
        CHECK(file_size(path) == size);
    }
    fail_stage = -1;
    /* One stale draft stops the whole batch. */
    PureDraft *other;
    CHECK(pure_draft_open(path, "beta", &other) == PURE_OK);
    CHECK(pure_draft_splice(other, 0, 0, (PureSpan){(const unsigned char *)"x", 1}) == PURE_OK);
    CHECK(pure_draft_commit(other, &revision) == PURE_OK && revision == 3);
    pure_draft_close(other);
    CHECK(pure_draft_commit_all(drafts, 3, revisions) == PURE_CONFLICT && revisions[1] == 3);
    expect(path, "alpha", &alpha);
    pure_draft_close(drafts[1]);
    CHECK(pure_draft_open(path, "beta", &drafts[1]) == PURE_OK);
    CHECK(pure_draft_splice(drafts[1], 0, 0, (PureSpan){(const unsigned char *)"y", 1}) == PURE_OK);
    CHECK(pure_draft_commit_all(drafts, 3, revisions) == PURE_OK);
    CHECK(revisions[0] == 4 && revisions[1] == 4 && revisions[2] == 2);
    expect(path, "alpha", &(Oracle){(unsigned char *)"A", 1, 4});
    expect(path, "beta", &(Oracle){(unsigned char *)"yxB", 3, 4});
    expect_draft(drafts[2], &(Oracle){(unsigned char *)"state+", 6, 2}, scratch);
    /* Drafts continue from the new revisions. */
    CHECK(pure_draft_splice(drafts[0], 1, 0, (PureSpan){(const unsigned char *)"z", 1}) == PURE_OK);
    CHECK(pure_draft_commit_all(drafts, 1, revisions) == PURE_OK && revisions[0] == 5);
    /* Invalid batches change nothing. */
    PureDraft *twice[2] = {drafts[0], drafts[0]}, *anonymous = pure_draft_new();
    CHECK(pure_draft_commit_all(twice, 2, revisions) == PURE_INVALID);
    PureDraft *mixed[2] = {drafts[1], anonymous};
    CHECK(pure_draft_commit_all(mixed, 2, revisions) == PURE_INVALID);
    pure_draft_close(anonymous);
    for (unsigned i = 0; i < 3; ++i) pure_draft_close(drafts[i]);
    /* Runtime values are not documents: listings skip them and document
     * operations refuse their names. */
    char seen[256] = "";
    CHECK(pure_store_keys(path, list_key, seen) == PURE_OK && !strcmp(seen, "alpha,beta,"));
    CHECK(pure_store_put(path, ".values", 0, (PureSpan){(const unsigned char *)"x", 1}, &revision) != PURE_OK);
    /* Many keys, in no particular order, in one commit. */
    PureDraft *many[50];
    int64_t many_revisions[50];
    char key[16];
    for (unsigned i = 0; i < 50; ++i) {
        snprintf(key, sizeof(key), "k%02u", (i * 37) % 50);
        CHECK((i % 2 ? pure_state_open(path, key, &many[i]) : pure_draft_open(path, key, &many[i])) == PURE_OK);
        CHECK(pure_draft_splice(many[i], 0, 0, (PureSpan){(const unsigned char *)key, strlen(key)}) == PURE_OK);
    }
    CHECK(pure_draft_commit_all(many, 50, many_revisions) == PURE_OK);
    for (unsigned i = 0; i < 50; ++i) {
        CHECK(many_revisions[i] == 1);
        snprintf(key, sizeof(key), "k%02u", (i * 37) % 50);
        PureDraft *check;
        CHECK((i % 2 ? pure_state_open(path, key, &check) : pure_draft_open(path, key, &check)) == PURE_OK);
        expect_draft(check, &(Oracle){(unsigned char *)key, strlen(key), 1}, scratch);
        pure_draft_close(check);
        pure_draft_close(many[i]);
    }
}

/* A store handle shares one mapping among its drafts, sees commits made by
 * other writers when a draft opens, follows a compaction that replaced the
 * file, and maps a batch it committed once. */
static void store_handle(const char *path) {
    unsigned char scratch[64];
    int64_t revision, revisions[3];
    CHECK(pure_store_put(path, "shared", 0, (PureSpan){(const unsigned char *)"one", 3}, &revision) == PURE_OK);
    PureStore *store;
    CHECK(pure_store_open(path, &store) == PURE_OK);
    PureDraft *a, *b, *state, *bad;
    CHECK(pure_store_draft(store, "shared", &a) == PURE_OK);
    expect_draft(a, &(Oracle){(unsigned char *)"one", 3, 1}, scratch);
    CHECK(pure_store_draft(store, "bad.key", &bad) == PURE_INVALID && !bad);
    /* Another writer commits: the next draft sees it, the open one keeps its version. */
    CHECK(pure_store_put(path, "shared", 1, (PureSpan){(const unsigned char *)"two", 3}, &revision) == PURE_OK);
    CHECK(pure_store_draft(store, "shared", &b) == PURE_OK);
    expect_draft(b, &(Oracle){(unsigned char *)"two", 3, 2}, scratch);
    expect_draft(a, &(Oracle){(unsigned char *)"one", 3, 1}, scratch);
    CHECK(pure_draft_splice(a, 3, 0, (PureSpan){(const unsigned char *)"!", 1}) == PURE_OK);
    CHECK(pure_draft_commit(a, &revision) == PURE_CONFLICT && revision == 2);
    pure_draft_close(a);
    /* A batch of handle drafts, a runtime value among them. */
    CHECK(pure_store_state(store, "values", &state) == PURE_OK && pure_draft_revision(state) == 0);
    CHECK(pure_store_draft(store, "other", &a) == PURE_OK);
    CHECK(pure_draft_splice(b, 3, 0, (PureSpan){(const unsigned char *)"+", 1}) == PURE_OK);
    CHECK(pure_draft_splice(state, 0, 0, (PureSpan){(const unsigned char *)"v", 1}) == PURE_OK);
    CHECK(pure_draft_splice(a, 0, 0, (PureSpan){(const unsigned char *)"o", 1}) == PURE_OK);
    PureDraft *batch[3] = {b, state, a};
    CHECK(pure_draft_commit_all(batch, 3, revisions) == PURE_OK && revisions[0] == 3 && revisions[1] == 1);
    expect(path, "shared", &(Oracle){(unsigned char *)"two+", 4, 3});
    expect_draft(state, &(Oracle){(unsigned char *)"v", 1, 1}, scratch);
    /* Other writers grow the file past compaction: it is replaced under the handle. */
    unsigned char *big = malloc(100000);
    uint32_t seed = 5;
    CHECK(big);
    fill(big, 100000, &seed);
    int64_t filler = 0;
    char name[512];
    struct stat before, replaced;
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    CHECK(stat(name, &before) == 0);
    for (int i = 0; i < 8; ++i) CHECK(pure_store_put(path, "filler", filler, (PureSpan){big, 100000}, &filler) == PURE_OK);
    CHECK(stat(name, &replaced) == 0 && replaced.st_ino != before.st_ino);
    free(big);
    PureDraft *after;
    CHECK(pure_store_draft(store, "shared", &after) == PURE_OK);
    expect_draft(after, &(Oracle){(unsigned char *)"two+", 4, 3}, scratch);
    /* Drafts of the old file still read and commit (their extents are copied). */
    expect_draft(b, &(Oracle){(unsigned char *)"two+", 4, 3}, scratch);
    CHECK(pure_draft_splice(b, 0, 0, (PureSpan){(const unsigned char *)">", 1}) == PURE_OK);
    CHECK(pure_draft_commit(b, &revision) == PURE_OK && revision == 4);
    expect(path, "shared", &(Oracle){(unsigned char *)">two+", 5, 4});
    pure_draft_close(after);
    pure_draft_close(a);
    pure_draft_close(b);
    pure_draft_close(state);
    pure_store_close(store);
}

/* Threads of one process commit through their own handles at once: none is
 * refused as busy, every commit lands, and edits of one shared key conflict
 * instead of overwriting each other. */
typedef struct { const char *path; unsigned number, conflicts; } Committer;

static void *commit_many(void *context) {
    Committer *c = context;
    PureStore *store;
    CHECK(pure_store_open(c->path, &store) == PURE_OK);
    char key[16];
    snprintf(key, sizeof(key), "t%u", c->number);
    for (unsigned i = 0; i < 40; ++i) {
        PureDraft *own, *shared;
        int64_t revisions[2];
        CHECK(pure_store_draft(store, key, &own) == PURE_OK && pure_store_draft(store, "shared", &shared) == PURE_OK);
        CHECK(pure_draft_splice(own, pure_draft_size(own), 0, (PureSpan){(const unsigned char *)"x", 1}) == PURE_OK);
        CHECK(pure_draft_splice(shared, pure_draft_size(shared), 0, (PureSpan){(const unsigned char *)"y", 1}) == PURE_OK);
        PureDraft *batch[2] = {own, shared};
        PureResult result = pure_draft_commit_all(batch, 2, revisions);
        CHECK(result == PURE_OK || result == PURE_CONFLICT);
        if (result == PURE_CONFLICT) {
            ++c->conflicts;
            CHECK(pure_draft_commit(own, &revisions[0]) == PURE_OK);
        }
        pure_draft_close(own);
        pure_draft_close(shared);
    }
    pure_store_close(store);
    return NULL;
}

static void threads(const char *path) {
    pthread_t thread[4];
    Committer committer[4];
    for (unsigned i = 0; i < 4; ++i) {
        committer[i] = (Committer){path, i, 0};
        CHECK(pthread_create(&thread[i], NULL, commit_many, &committer[i]) == 0);
    }
    unsigned conflicts = 0;
    for (unsigned i = 0; i < 4; ++i) {
        CHECK(pthread_join(thread[i], NULL) == 0);
        conflicts += committer[i].conflicts;
    }
    PureStoredView view;
    char key[16];
    for (unsigned i = 0; i < 4; ++i) {
        snprintf(key, sizeof(key), "t%u", i);
        CHECK(pure_store_get(path, key, PURE_OBJECT_LIMIT, &view) == PURE_OK && view.body.size == 40 && view.revision == 40);
        pure_store_release(&view);
    }
    CHECK(pure_store_get(path, "shared", PURE_OBJECT_LIMIT, &view) == PURE_OK);
    CHECK(view.body.size == 160 - conflicts && view.revision == (int64_t)(160 - conflicts));
    pure_store_release(&view);
}

/* Commits that arrive while another is being published share the next
 * publication: one head for all of them. */
typedef struct { const char *path; unsigned number; PureResult result; } Single;

static void *commit_one(void *context) {
    Single *s = context;
    PureStore *store;
    PureDraft *draft;
    char key[16];
    int64_t revision;
    snprintf(key, sizeof(key), "g%u", s->number);
    CHECK(pure_store_open(s->path, &store) == PURE_OK && pure_store_draft(store, key, &draft) == PURE_OK);
    CHECK(pure_draft_splice(draft, 0, 0, (PureSpan){(const unsigned char *)key, strlen(key)}) == PURE_OK);
    s->result = pure_draft_commit(draft, &revision);
    CHECK(s->result != PURE_OK || revision == 1);
    pure_draft_close(draft);
    pure_store_close(store);
    return NULL;
}

static void grouped(const char *path) {
    pthread_t thread[5];
    Single single[5];
    unsigned long before = pure_tree_test_publications();
    __atomic_store_n(&slow_once, 1, __ATOMIC_SEQ_CST);
    for (unsigned i = 0; i < 5; ++i) {
        single[i] = (Single){path, i, PURE_INVALID};
        CHECK(pthread_create(&thread[i], NULL, commit_one, &single[i]) == 0);
        if (!i) pause_ms(20); /* the first is now publishing, slowly */
    }
    for (unsigned i = 0; i < 5; ++i) CHECK(pthread_join(thread[i], NULL) == 0 && single[i].result == PURE_OK);
    CHECK(pure_tree_test_publications() - before == 2);
    char key[16];
    for (unsigned i = 0; i < 5; ++i) {
        snprintf(key, sizeof(key), "g%u", i);
        expect(path, key, &(Oracle){(unsigned char *)key, strlen(key), 1});
    }
}

/* A crash during a commit's only sync can leave its head on the device
 * without all of its bytes. A process that starts after it passes over that
 * head to the previous commit, and the next writer overwrites both. */
static void lost_commit(const char *path) {
    unsigned char first[] = "first", second[] = "second";
    int64_t revision;
    CHECK(pure_store_put(path, "lost", 0, (PureSpan){first, 5}, &revision) == PURE_OK);
    Oracle o = {first, 5, revision};
    uint64_t start = published_end(path, "lost");
    CHECK(pure_store_put(path, "lost", o.revision, (PureSpan){second, 6}, &revision) == PURE_OK);
    uint64_t end = published_end(path, "lost");
    char name[512];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    int fd = open(name, O_RDWR);
    off_t at = (off_t)(start + (end - start) / 2);
    unsigned char byte;
    CHECK(fd >= 0 && pread(fd, &byte, 1, at) == 1);
    byte ^= 0xff;
    CHECK(pwrite(fd, &byte, 1, at) == 1 && close(fd) == 0);
    pure_tree_test_forget();
    expect(path, "lost", &o);
    PureStore *store;
    PureDraft *draft;
    CHECK(pure_store_open(path, &store) == PURE_OK && pure_store_draft(store, "lost", &draft) == PURE_OK);
    CHECK(pure_draft_revision(draft) == o.revision);
    pure_draft_close(draft);
    CHECK(pure_store_put(path, "lost", o.revision + 1, (PureSpan){first, 1}, &revision) == PURE_CONFLICT);
    CHECK(pure_store_put(path, "lost", o.revision, (PureSpan){second, 3}, &revision) == PURE_OK);
    o = (Oracle){second, 3, revision};
    CHECK(published_end(path, "lost") < end); /* it started where the lost commit did */
    CHECK(pure_store_draft(store, "lost", &draft) == PURE_OK && pure_draft_revision(draft) == o.revision);
    pure_draft_close(draft);
    pure_store_close(store);
    pure_tree_test_forget();
    expect(path, "lost", &o);
}

/* While a commit's sync is pending, this process keeps reading the previous
 * version: a crash could still take the new one back. */
static void *commit_held(void *context) {
    int64_t revision;
    CHECK(pure_store_put(context, "pending", 1, (PureSpan){(const unsigned char *)"new", 3}, &revision) == PURE_OK);
    return NULL;
}

static void pending_head(const char *path) {
    int64_t revision;
    CHECK(pure_store_put(path, "pending", 0, (PureSpan){(const unsigned char *)"old", 3}, &revision) == PURE_OK);
    PureStore *store;
    PureDraft *draft;
    CHECK(pure_store_open(path, &store) == PURE_OK);
    __atomic_store_n(&held_sync, 1, __ATOMIC_SEQ_CST);
    pthread_t writer;
    CHECK(pthread_create(&writer, NULL, commit_held, (void *)path) == 0);
    while (__atomic_load_n(&held_sync, __ATOMIC_SEQ_CST) != 2) pause_ms(1);
    CHECK(pure_store_draft(store, "pending", &draft) == PURE_OK && pure_draft_revision(draft) == 1);
    pure_draft_close(draft);
    expect(path, "pending", &(Oracle){(unsigned char *)"old", 3, 1});
    __atomic_store_n(&held_sync, 0, __ATOMIC_SEQ_CST);
    CHECK(pthread_join(writer, NULL) == 0);
    CHECK(pure_store_draft(store, "pending", &draft) == PURE_OK && pure_draft_revision(draft) == 2);
    pure_draft_close(draft);
    pure_store_close(store);
    expect(path, "pending", &(Oracle){(unsigned char *)"new", 3, 2});
}

/* A commit costs one sync, and commits into the written zeros after the end
 * leave the file size alone (no journal commit for a new size). */
static void one_sync(const char *path) {
    int64_t revision;
    CHECK(pure_store_put(path, "sync", 0, (PureSpan){(const unsigned char *)"0", 1}, &revision) == PURE_OK);
    uint64_t size = file_size(path);
    unsigned long syncs = pure_tree_test_syncs();
    for (unsigned i = 0; i < 20; ++i)
        CHECK(pure_store_put(path, "sync", revision, (PureSpan){(const unsigned char *)"x", 1}, &revision) == PURE_OK);
    CHECK(pure_tree_test_syncs() - syncs == 20 && file_size(path) == size);
}

/* A compacted file carries written zeros for its whole cycle: once the sizes
 * settle, the commits between two compactions never grow the file (no new
 * blocks, no journal commit for them). When the live data shrinks, the file
 * shrinks with it. */
static void cycles(const char *path) {
    char name[512], key[16];
    snprintf(name, sizeof(name), "%s/pure.tree", path);
    unsigned char big[4096], small[64];
    memset(big, 'b', sizeof(big));
    memset(small, 's', sizeof(small));
    int64_t revisions[32] = {0};
    struct stat was, now;
    CHECK(stat(name, &was) == 0);
    unsigned compactions = 0, grown = 0, sized = 0;
    uint64_t largest = 0;
    for (unsigned i = 0; i < 1600; ++i) {
        snprintf(key, sizeof(key), "c%u", i % 32);
        CHECK(pure_store_put(path, key, revisions[i % 32], (PureSpan){big, sizeof(big)}, &revisions[i % 32]) == PURE_OK);
        CHECK(stat(name, &now) == 0);
        /* Once the 32 values all exist (after the first compaction past them
         * the next compacted file is sized for them), no cycle grows. */
        if (now.st_ino != was.st_ino) {
            if (i >= 32 && !sized) sized = compactions + 2;
            ++compactions;
        } else if (sized && compactions >= sized && now.st_size != was.st_size) ++grown;
        if ((uint64_t)now.st_size > largest) largest = (uint64_t)now.st_size;
        was = now;
    }
    CHECK(sized && compactions >= sized + 4 && grown == 0);
    /* The same keys with small values: a few compactions later the file is
     * down to the least a fresh file has (its data and 256 KiB of zeros). */
    unsigned settled = compactions;
    for (unsigned i = 0; i < 20000 && compactions < settled + 3; ++i) {
        snprintf(key, sizeof(key), "c%u", i % 32);
        CHECK(pure_store_put(path, key, revisions[i % 32], (PureSpan){small, sizeof(small)}, &revisions[i % 32]) == PURE_OK);
        CHECK(stat(name, &now) == 0);
        if (now.st_ino != was.st_ino) ++compactions;
        was = now;
    }
    CHECK(compactions == settled + 3 && (uint64_t)now.st_size < largest / 2);
}

static void clean(const char *path) {
    DIR *entries = opendir(path);
    CHECK(entries);
    struct dirent *entry;
    while ((entry = readdir(entries))) {
        if (!strcmp(entry->d_name, ".") || !strcmp(entry->d_name, "..")) continue;
        CHECK(strncmp(entry->d_name, ".pending-", 9));
        CHECK(unlinkat(dirfd(entries), entry->d_name, 0) == 0);
    }
    CHECK(closedir(entries) == 0 && rmdir(path) == 0);
}

int main(void) {
    void (*checks[])(const char *) = {oracle, amplification, faults, crashes, torn_head,
                                      isolation, corruption, many_keys, revision_limit, keys,
                                      drafts, typing, draft_conflict, draft_relocation, draft_faults,
                                      draft_versions, anonymous_draft, batch, store_handle, threads, grouped,
                                      lost_commit, pending_head, one_sync, records, cycles};
    for (size_t i = 0; i < sizeof(checks) / sizeof(*checks); ++i) {
        char path[] = "/tmp/pure-tree-check-XXXXXX";
        CHECK(mkdtemp(path) && pure_store_init(path) == PURE_OK);
        checks[i](path);
        CHECK(pure_store_init(path) == PURE_OK);
        clean(path);
    }
    puts("{\"tree_store\":\"random-oracle-balance-held-views-one-byte-amplification-faults-"
         "process-crash-torn-head-lockless-isolation-compaction-corruption-1024-keys-revision-limit-key-listing-"
         "draft-oracle-typing-arena-conflict-relocation-commit-faults-held-versions-anonymous-"
         "atomic-batch-runtime-keys-store-handle-threads-group-commit-lost-commit-pending-head-one-sync-records-"
         "cycles\"}");
    return 0;
}