#define _DEFAULT_SOURCE
#include "vega.h"
#include "module-store.h"
#include "store.h"
#include <poll.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>

/* vega SURFACE MODULE [--store PATH]: one module, one screen, several surfaces.
 *   check            what the module seems to mean but does not meet (exit 1)
 *   tui              interactive terminal
 *   tui --dump WxH   the terminal's frames as text, driven by a script
 *   tui --paint WxH  the bytes each frame sends to the terminal, driven by a script
 *   cli              plain lines for pipes, driven by a script
 *   say              sentences (the first natural-language surface), driven by a script
 *   web [--listen ADDRESS] [--port N]
 *                    a web page (a GUI), on 127.0.0.1 unless another address is given
 *   pixels --symbols FONT.vsym [--size PX] --grid WxH --out PREFIX
 *                    the TUI's frames drawn with a font's glyphs, driven by a
 *                    script: each show writes PREFIX-N.ppm after the text
 *   display --symbols FONT.vsym [--size PX] [--card PATH] [--writeback WxH --out PREFIX]
 *                    the same on a display through KMS, as many cells as fit,
 *                    driven by a script; with writeback each shown frame comes
 *                    back from the display controller, is set against what was
 *                    drawn and written to PREFIX-N.ppm
 * With --store the app's states live in that tree store: the app continues
 * where it was, whichever surface runs it. With --watch (tui, web) a module
 * written again replaces the running one and states keep their values by
 * name: aup watch app.aup -o app.pmod beside it makes a saved edit show at once.
 * Script commands, one per line: key KEYNAME | text HEX|- | type HEX | enter |
 * tab | frame [N] | point VIEW ROW | click LINE COLUMN | time MS | tick TIMER | swap MODULE | show. key presses and
 * releases the input bound to that key; text commits text to the screen's text
 * input; type, enter and tab act on the TUI's input line; point focuses a row
 * (0 first) of a list or table; click is a mouse click on the last shown TUI
 * frame (1 first, as terminals report it); time sets the time the next
 * events see (live surfaces use the clock) and tick ticks a timer (live
 * surfaces tick them on time); swap replaces the module as --watch does. */

static PureModule modules[2]; /* the running one (app.module) and the next */
static unsigned current;
static PureApp app;
static VegaScreen screen;
static VegaGrid *drawn; /* the TUI's last frame, which a click lands on */
static char entry[VEGA_TEXT];
static size_t entry_length;
static bool typing;

/* The module file last read, and a digest of its bytes. A loaded module
 * keeps nothing of them, so one buffer, grown to the largest, serves every load. */
static unsigned char *module_bytes;
static size_t module_capacity;
static uint64_t module_digest;

/* Read a module file whole into module_bytes: its size, or -1. */
static long read_module(const char *path) {
    FILE *file = fopen(path, "rb");
    size_t size = 0;
    bool ok = file != NULL;
    while (ok && !feof(file)) {
        if (size == module_capacity) {
            size_t capacity = module_capacity ? module_capacity * 2 : 1 << 16;
            unsigned char *grown = capacity <= (8u << 20) ? realloc(module_bytes, capacity) : NULL;
            if (!grown) { ok = false; break; }
            module_bytes = grown;
            module_capacity = capacity;
        }
        size += fread(module_bytes + size, 1, module_capacity - size, file);
        ok = !ferror(file);
    }
    if (file) fclose(file);
    if (!ok) return -1;
    uint64_t h = UINT64_C(0xcbf29ce484222325) ^ size;
    for (size_t i = 0; i < size; ++i) h = (h ^ module_bytes[i]) * UINT64_C(0x100000001b3);
    module_digest = h;
    return (long)size;
}

/* Decode the module that read_module read from path. */
static bool decode(const char *path, long size, PureModule *module) {
    if (size < 0) { fprintf(stderr, "vega: cannot read %s\n", path); return false; }
    char error[128];
    if (pure_module_load(module_bytes, (size_t)size, module, error, sizeof(error)) != PURE_OK) {
        fprintf(stderr, "vega: %s: %s\n", path, error);
        return false;
    }
    return true;
}

static bool load_module(const char *path, PureModule *module) { return decode(path, read_module(path), module); }

static void print_finding(void *path, const char *name, const char *message) {
    printf("%s: %s: %s\n", (const char *)path, name, message);
}

static bool load(const char *path, const char *store) {
    if (!load_module(path, &modules[current])) return false;
    if (store && pure_store_init(store) != PURE_OK) { fprintf(stderr, "vega: cannot open store %s\n", store); return false; }
    PureResult started = pure_app_start(&app, &modules[current], store ? pure_tree_data(store) : (PureData){0});
    if (started != PURE_OK) { fprintf(stderr, "vega: cannot start (%d)\n", (int)started); return false; }
    vega_screen(&screen, &modules[current]);
    typing = screen.prompt >= 0;
    return true;
}

/* Replace the running app's module with the one read from path, states
 * keeping their values by name; a module that does not load or replace
 * leaves the app as it was. */
static bool swap(const char *path, long size) {
    PureModule *next = &modules[!current];
    if (!decode(path, size, next)) return false;
    PureResult replaced = pure_app_replace(&app, next);
    if (replaced != PURE_OK) {
        fprintf(stderr, "vega: keeping the running module: cannot replace it (%d)\n", (int)replaced);
        return false;
    }
    bool had_prompt = screen.prompt >= 0;
    current = !current;
    vega_screen(&screen, next);
    typing = screen.prompt >= 0 && (typing || !had_prompt);
    return true;
}

/* --watch: the module file's bytes when last read (their digest), so a
 * module written again is seen however soon and whatever its size or file
 * times. Read at most five times a second, however often asked; bytes that
 * do not load are not tried again. */
static const char *watched;
static uint64_t watched_digest;
static struct timespec watched_at;

static bool module_changed(void) {
    struct timespec now;
    clock_gettime(CLOCK_MONOTONIC, &now);
    if (!watched || (now.tv_sec - watched_at.tv_sec) * 1000000000L + now.tv_nsec - watched_at.tv_nsec < 200000000L)
        return false;
    watched_at = now;
    long size = read_module(watched);
    if (size < 0 || module_digest == watched_digest) return false; /* a missing file is looked for again */
    watched_digest = module_digest;
    return swap(watched, size);
}

static int key_input(const char *key) { return vega_key_input(app.module, key); }

/* A key press and release; false when the app has no such key or the press failed. */
static bool press(const char *key, int *input) {
    *input = key_input(key);
    return *input >= 0 && vega_press(&app, key);
}

static bool commit(const char *text, size_t length) { return vega_commit(&app, &screen, text, length); }

static const VegaPart *part_named(const char *name) {
    for (unsigned i = 0; i < screen.count; ++i)
        if (screen.parts[i].kind != VEGA_FIELD && !strcmp(app.module->view_names[screen.parts[i].view], name))
            return &screen.parts[i];
    return NULL;
}

/* A mouse button on a line of the last frame: a click focuses the row there;
 * the wheel moves the focus of the list or table under it. */
static bool mouse(unsigned button, unsigned line) {
    unsigned index;
    size_t item;
    if (!drawn || !vega_hit(drawn, line, &index, &item)) return false;
    const VegaPart *part = &screen.parts[index];
    if (button == 64 || button == 65) {
        size_t focus = vega_focus(&app, part), rows = vega_rows(&app, part);
        if (focus < rows) { /* else the wheel focuses the row under it */
            if (button == 64 ? !focus : focus + 1 >= rows) return false;
            item = button == 64 ? focus - 1 : focus + 1;
        }
    } else if (button) return false;
    return vega_point(&app, part, item);
}

static int hex(char c) { return c >= '0' && c <= '9' ? c - '0' : c >= 'a' && c <= 'f' ? c - 'a' + 10 : -1; }

static size_t unhex(const char *digits, char *out, size_t size) {
    size_t length = 0;
    if (!strcmp(digits, "-")) return 0;
    for (size_t i = 0; digits[i] && digits[i + 1] && length < size; i += 2)
        if (hex(digits[i]) >= 0 && hex(digits[i + 1]) >= 0) out[length++] = (char)(hex(digits[i]) << 4 | hex(digits[i + 1]));
    return length;
}

/* ---- terminal ------------------------------------------------------- */

typedef struct { char *bytes; size_t used, capacity; } Out;

static void out_put(Out *out, const char *bytes, size_t size) {
    if (out->used + size > out->capacity) {
        size_t capacity = out->capacity ? out->capacity : 4096;
        while (capacity < out->used + size) capacity *= 2;
        char *grown = realloc(out->bytes, capacity);
        if (!grown) return;
        out->bytes = grown;
        out->capacity = capacity;
    }
    memcpy(out->bytes + out->used, bytes, size);
    out->used += size;
}

static void out_codepoint(Out *out, uint32_t c) {
    char b[4];
    size_t n = c < 0x80 ? 1 : c < 0x800 ? 2 : c < 0x10000 ? 3 : 4;
    if (n == 1) b[0] = (char)c;
    else if (n == 2) { b[0] = (char)(0xC0 | c >> 6); b[1] = (char)(0x80 | (c & 0x3F)); }
    else if (n == 3) { b[0] = (char)(0xE0 | c >> 12); b[1] = (char)(0x80 | (c >> 6 & 0x3F)); b[2] = (char)(0x80 | (c & 0x3F)); }
    else {
        b[0] = (char)(0xF0 | c >> 18); b[1] = (char)(0x80 | (c >> 12 & 0x3F));
        b[2] = (char)(0x80 | (c >> 6 & 0x3F)); b[3] = (char)(0x80 | (c & 0x3F));
    }
    out_put(out, b, n);
}

static const char *const tone_names[VEGA_TONES] = {"normal", "muted", "accent", "good", "warning", "danger"};

/* The grid as text, one line per row: '>' marks a focused row, and a row's
 * tone (of its first character) follows a tab when it is not normal. */
static void dump(const VegaGrid *grid) {
    Out out = {0};
    for (unsigned r = 0; r < grid->height; ++r) {
        const VegaCell *line = grid->cells + (size_t)r * grid->width;
        bool focus = false;
        int tone = -1;
        size_t start = out.used, end;
        for (unsigned c = 0; c < grid->width; ++c) {
            focus = focus || line[c].focus;
            if (tone < 0 && line[c].ch && line[c].ch != ' ') tone = line[c].tone;
        }
        out_put(&out, focus ? ">" : "|", 1);
        for (unsigned c = 0; c < grid->width; ++c) {
            if (!line[c].ch) continue;
            out_codepoint(&out, line[c].ch);
            if (line[c].mark) out_codepoint(&out, line[c].mark);
        }
        end = out.used;
        while (end > start + 1 && out.bytes[end - 1] == ' ') --end;
        out.used = end;
        if (tone > 0) { out_put(&out, "\t", 1); out_put(&out, tone_names[tone], strlen(tone_names[tone])); }
        out_put(&out, "\n", 1);
    }
    fwrite(out.bytes, 1, out.used, stdout);
    free(out.bytes);
}

static const char *const sgr_tones[VEGA_TONES] = {"", ";2", ";1;36", ";32", ";33", ";31"};

static bool same_cell(const VegaCell *a, const VegaCell *b) {
    return a->ch == b->ch && a->mark == b->mark && a->tone == b->tone && a->focus == b->focus && a->strong == b->strong;
}

/* The terminal bytes that turn what it shows into the grid: each run of
 * changed cells after a cursor move (a short unchanged gap stays in the run,
 * being cheaper than another move), everything after a resize. */
static void paint(VegaGrid *grid, Out *out) {
    bool all = !grid->painted;
    int style = -1;
    char code[48];
    if (all) out_put(out, "\033[2J", 4);
    for (unsigned r = 0; r < grid->height; ++r) {
        const VegaCell *line = grid->cells + (size_t)r * grid->width, *old = grid->shown + (size_t)r * grid->width;
        for (unsigned c = 0; c < grid->width;) {
            if (!all && same_cell(&line[c], &old[c])) { ++c; continue; }
            unsigned start = c, end = c + 1;
            for (unsigned k = c + 1, gap = 0; k < grid->width && gap <= 6; ++k) {
                if (all || !same_cell(&line[k], &old[k])) { end = k + 1; gap = 0; }
                else ++gap;
            }
            while (start && !line[start].ch) --start; /* the second half of a wide character: from its first */
            out_put(out, code, (size_t)snprintf(code, sizeof(code), "\033[%u;%uH", r + 1, start + 1));
            for (unsigned k = start; k < end; ++k) {
                if (!line[k].ch) continue;
                int next = line[k].tone | line[k].focus << 4 | line[k].strong << 5;
                if (next != style) {
                    out_put(out, code, (size_t)snprintf(code, sizeof(code), "\033[0%s%s%sm", line[k].strong ? ";1" : "",
                                                         line[k].focus ? ";7" : "",
                                                         sgr_tones[line[k].tone < VEGA_TONES ? line[k].tone : 0]));
                    style = next;
                }
                out_codepoint(out, line[k].ch);
                if (line[k].mark) out_codepoint(out, line[k].mark);
            }
            c = end;
        }
    }
    if (style > 0) out_put(out, "\033[0m", 4);
    if (grid->cursor_row >= 0)
        out_put(out, code, (size_t)snprintf(code, sizeof(code), "\033[%d;%dH\033[?25h", grid->cursor_row + 1,
                                             grid->cursor_column + 1));
    else out_put(out, "\033[?25l", 6);
    memcpy(grid->shown, grid->cells, (size_t)grid->width * grid->height * sizeof(*grid->cells));
    grid->painted = true;
}

static void paint_terminal(VegaGrid *grid) {
    Out out = {0};
    paint(grid, &out);
    if (write(STDOUT_FILENO, out.bytes, out.used) < 0) { /* the terminal went away; the loop ends on read */ }
    free(out.bytes);
}

static struct termios saved_terminal;
static bool raw_terminal;
static volatile sig_atomic_t resized = 1;

static void on_resize(int signal_number) { (void)signal_number; resized = 1; }

static void restore_terminal(void) {
    if (!raw_terminal) return;
    tcsetattr(STDIN_FILENO, TCSAFLUSH, &saved_terminal);
    const char *leave = "\033[?1006l\033[?1000l\033[0m\033[?25h\033[?1049l";
    if (write(STDOUT_FILENO, leave, strlen(leave)) < 0) { /* nothing left to tell */ }
    raw_terminal = false;
}

static bool raw_mode(void) {
    if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || tcgetattr(STDIN_FILENO, &saved_terminal)) return false;
    struct termios t = saved_terminal;
    t.c_iflag &= ~(tcflag_t)(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
    t.c_oflag &= ~(tcflag_t)OPOST;
    t.c_cflag |= CS8;
    t.c_lflag &= ~(tcflag_t)(ECHO | ICANON | IEXTEN | ISIG);
    t.c_cc[VMIN] = 1;
    t.c_cc[VTIME] = 0;
    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &t)) return false;
    raw_terminal = true;
    atexit(restore_terminal);
    const char *enter = "\033[?1049h\033[?25l\033[?1000h\033[?1006h"; /* mouse buttons, reported as SGR */
    return write(STDOUT_FILENO, enter, strlen(enter)) >= 0;
}

/* Whether the app takes Tab itself; otherwise Tab switches typing and keys. */
static bool tab_switches(void) { return screen.prompt >= 0 && key_input("Tab") < 0; }

/* One key from the terminal, as typed text or as a Pure key name. */
static void handle_key(const char *name) {
    int input;
    if (!strcmp(name, "Tab") && tab_switches()) { typing = !typing; return; }
    if (typing && !strcmp(name, "Enter")) {
        if (entry_length && commit(entry, entry_length)) entry_length = 0;
        return;
    }
    if (typing && !strcmp(name, "Backspace")) {
        while (entry_length && ((unsigned char)entry[entry_length - 1] & 0xC0) == 0x80) --entry_length;
        if (entry_length) --entry_length;
        return;
    }
    press(name, &input);
}

static void handle_text(const char *bytes, size_t length) {
    if (typing) {
        if (entry_length + length < sizeof(entry)) { memcpy(entry + entry_length, bytes, length); entry_length += length; }
        return;
    }
    if (length != 1) return;
    char c = bytes[0], name[16];
    if (c == ' ') strcpy(name, "Space");
    else if (c >= 'a' && c <= 'z') snprintf(name, sizeof(name), "Key%c", c - 'a' + 'A');
    else if (c >= 'A' && c <= 'Z') snprintf(name, sizeof(name), "Key%c", c);
    else if (c >= '0' && c <= '9') snprintf(name, sizeof(name), "Digit%c", c);
    else return;
    handle_key(name);
}

/* Parse terminal input: escape sequences, control keys and UTF-8 text. */
static bool handle_input(const unsigned char *in, size_t length) {
    static const struct { const char *sequence, *key; } sequences[] = {
        {"[A", "ArrowUp"}, {"[B", "ArrowDown"}, {"[C", "ArrowRight"}, {"[D", "ArrowLeft"}, {"[H", "Home"},
        {"[F", "End"}, {"OA", "ArrowUp"}, {"OB", "ArrowDown"}, {"OC", "ArrowRight"}, {"OD", "ArrowLeft"},
        {"OH", "Home"}, {"OF", "End"}, {"[1~", "Home"}, {"[7~", "Home"}, {"[4~", "End"}, {"[8~", "End"},
        {"[3~", "Delete"}, {"[5~", "PageUp"}, {"[6~", "PageDown"}};
    for (size_t at = 0; at < length;) {
        unsigned char c = in[at];
        if (c == 0x03 || c == 0x11) return false; /* Ctrl-C, Ctrl-Q */
        if (c == 0x1B && at + 2 < length && in[at + 1] == '[' && in[at + 2] == '<') {
            /* A mouse report: ESC [ < button ; column ; line, M on press, m on release. */
            unsigned fields[3] = {0, 0, 0}, field = 0;
            size_t end = at + 3;
            for (; end < length && field < 3; ++end) {
                if (in[end] >= '0' && in[end] <= '9') fields[field] = fields[field] * 10 + (unsigned)(in[end] - '0');
                else if (in[end] == ';') ++field;
                else break;
            }
            if (end < length && in[end] == 'M' && field == 2 && fields[2]) mouse(fields[0], fields[2] - 1);
            at = end + 1;
            continue;
        }
        if (c == 0x1B) {
            size_t matched = 0;
            for (size_t i = 0; i < sizeof(sequences) / sizeof(*sequences) && !matched; ++i) {
                size_t n = strlen(sequences[i].sequence);
                if (at + 1 + n <= length && !memcmp(in + at + 1, sequences[i].sequence, n)) {
                    handle_key(sequences[i].key);
                    matched = 1 + n;
                }
            }
            if (!matched) { handle_key("Escape"); matched = 1; }
            at += matched;
            continue;
        }
        if (c == '\r' || c == '\n') handle_key("Enter");
        else if (c == 0x7F || c == 0x08) handle_key("Backspace");
        else if (c == '\t') handle_key("Tab");
        else if (c >= 0x20) {
            size_t n = c < 0x80 ? 1 : c < 0xE0 ? 2 : c < 0xF0 ? 3 : 4;
            if (at + n > length) n = length - at;
            handle_text((const char *)in + at, n);
            at += n;
            continue;
        }
        ++at;
    }
    return true;
}

static int interactive(void) {
    if (!raw_mode()) { fputs("vega: the tui needs a terminal (or use --dump WxH)\n", stderr); return 2; }
    signal(SIGWINCH, on_resize);
    VegaGrid grid = {0};
    drawn = &grid;
    VegaTimers timers;
    vega_timers_start(&timers, app.module, vega_now());
    for (;;) {
        if (resized) {
            struct winsize size;
            resized = 0;
            if (!ioctl(STDOUT_FILENO, TIOCGWINSZ, &size) && size.ws_col && size.ws_row)
                vega_grid(&grid, size.ws_col, size.ws_row);
            else vega_grid(&grid, 80, 24);
        }
        /* Tick what is due, draw, then wait for input, a frame or the next tick. */
        bool ticked = false;
        long due = vega_timers_run(&timers, &app, vega_now(), &ticked);
        vega_draw(&grid, &app, &screen, entry, entry_length, typing);
        paint_terminal(&grid);
        struct pollfd wait = {STDIN_FILENO, POLLIN, 0};
        int timeout = screen.ticks ? 16 : watched ? 200 : -1;
        if (due >= 0 && (timeout < 0 || due < timeout)) timeout = (int)due;
        int ready = poll(&wait, 1, timeout);
        app.now = vega_now();
        if (ready == 0) {
            if (screen.ticks) pure_app_frame(&app);
            if (module_changed()) vega_timers_start(&timers, app.module, app.now);
            continue;
        }
        if (ready < 0) continue; /* a signal, such as a resize */
        unsigned char in[256];
        ssize_t got = read(STDIN_FILENO, in, sizeof(in));
        if (got <= 0 || !handle_input(in, (size_t)got)) break;
    }
    restore_terminal();
    drawn = NULL;
    vega_grid_free(&grid);
    return 0;
}

/* ---- scripts -------------------------------------------------------- */

typedef enum { SURFACE_CLI, SURFACE_SAY, SURFACE_TUI, SURFACE_WEB, SURFACE_PIXELS, SURFACE_DISPLAY } Surface;

/* The pixel surface's font and where its frames go. */
static VegaFace face;
static const char *frames_prefix;
static unsigned frames;

/* A frame as a binary PPM (P6): prefix-N.ppm. */
static bool write_frame(const VegaGrid *grid, char path[512]) {
    int width = (int)grid->width * face.cell_width, height = (int)grid->height * face.cell_height;
    uint32_t *pixels = malloc((size_t)width * (size_t)height * sizeof(*pixels));
    unsigned char *bytes = malloc((size_t)width * (size_t)height * 3);
    bool ok = pixels && bytes;
    if (ok) {
        vega_pixels(grid, &face, pixels, (size_t)width);
        for (size_t i = 0; i < (size_t)width * (size_t)height; ++i) {
            bytes[3 * i] = (unsigned char)(pixels[i] >> 16);
            bytes[3 * i + 1] = (unsigned char)(pixels[i] >> 8);
            bytes[3 * i + 2] = (unsigned char)pixels[i];
        }
        snprintf(path, 512, "%s-%u.ppm", frames_prefix, ++frames);
        FILE *f = fopen(path, "wb");
        ok = f && fprintf(f, "P6\n%d %d\n255\n", width, height) > 0 &&
             fwrite(bytes, 3, (size_t)width * (size_t)height, f) == (size_t)width * (size_t)height;
        if (f && fclose(f)) ok = false;
    }
    free(pixels);
    free(bytes);
    return ok;
}

static VegaDisplay *display;

/* A frame on the display; with writeback, what came back is set against it
 * and written (differing: how many pixels are not what was drawn). */
static bool show_frame(const VegaGrid *grid, char path[512], unsigned long *differing) {
    unsigned width, height;
    size_t stride, captured_stride;
    uint32_t *out = vega_display_buffer(display, &width, &height, &stride);
    vega_pixels_clear(out, stride, width, height);
    vega_pixels(grid, &face, out, stride);
    if (!vega_display_show(display)) return false;
    const uint32_t *back = vega_display_captured(display, &captured_stride);
    *differing = 0;
    path[0] = 0;
    if (!back || !frames_prefix) return true;
    /* The capture read once, a row at a time (it is not cached memory either). */
    uint32_t *row = malloc((size_t)width * sizeof(*row));
    unsigned char *rgb = malloc((size_t)width * height * 3);
    bool ok = row && rgb;
    for (unsigned y = 0; ok && y < height; ++y) {
        memcpy(row, back + (size_t)y * captured_stride, (size_t)width * sizeof(*row));
        for (unsigned x = 0; x < width; ++x) {
            *differing += (row[x] & 0xffffff) != (out[(size_t)y * stride + x] & 0xffffff);
            unsigned char *p = rgb + ((size_t)y * width + x) * 3;
            p[0] = (unsigned char)(row[x] >> 16), p[1] = (unsigned char)(row[x] >> 8), p[2] = (unsigned char)row[x];
        }
    }
    snprintf(path, 512, "%s-%u.ppm", frames_prefix, ++frames);
    FILE *f = ok ? fopen(path, "wb") : NULL;
    ok = f && fprintf(f, "P6\n%u %u\n255\n", width, height) > 0 && fwrite(rgb, 3, (size_t)width * height, f) == (size_t)width * height;
    if (f && fclose(f)) ok = false;
    free(row);
    free(rgb);
    return ok;
}


/* painting: show writes the terminal bytes of the frame, not the grid. */
static int script(Surface surface, unsigned width, unsigned height, bool painting) {
    static char line[1 << 16];
    VegaGrid grid = {0};
    bool gridded = surface == SURFACE_TUI || surface == SURFACE_PIXELS || surface == SURFACE_DISPLAY;
    if (gridded && !vega_grid(&grid, width, height)) return 2;
    bool shown = false;
    drawn = gridded ? &grid : NULL;
    bool color = surface == SURFACE_CLI && isatty(STDOUT_FILENO) && !getenv("NO_COLOR");
    unsigned long counted = vega_evaluations();
    while (fgets(line, sizeof(line), stdin)) {
        char command[16] = "", argument[sizeof(line)] = "";
        line[strcspn(line, "\r\n")] = 0;
        if (sscanf(line, "%15s %65535s", command, argument) < 1) continue;
        bool acted = true, ok = true;
        int input = -1;
        const char *verb = "do that";
        if (!strcmp(command, "key")) {
            ok = press(argument, &input);
            if (input < 0) fprintf(stderr, "vega: no input answers %s\n", argument);
        } else if (!strcmp(command, "text")) {
            char text[VEGA_TEXT];
            ok = commit(text, unhex(argument, text, sizeof(text)));
        } else if (!strcmp(command, "type")) {
            entry_length += unhex(argument, entry + entry_length, sizeof(entry) - 1 - entry_length);
            acted = false;
        } else if (!strcmp(command, "enter")) {
            handle_key("Enter");
        } else if (!strcmp(command, "tab")) {
            handle_key("Tab");
            acted = false;
        } else if (!strcmp(command, "point")) {
            char name[PURE_MODULE_NAME];
            long row = -1;
            const VegaPart *part = sscanf(line, "%*s %31s %ld", name, &row) == 2 ? part_named(name) : NULL;
            verb = "point";
            if (!part) fprintf(stderr, "vega: no list or table %s\n", name);
            ok = part && row >= 0 && vega_point(&app, part, (size_t)row);
        } else if (!strcmp(command, "click")) {
            unsigned at_line = 0, at_column = 0;
            verb = "point";
            if (!gridded) { fputs("vega: click needs the tui or pixels\n", stderr); continue; }
            acted = sscanf(line, "%*s %u %u", &at_line, &at_column) == 2 && at_line && shown;
            ok = acted && mouse(0, at_line - 1);
        } else if (!strcmp(command, "time")) {
            /* The time the next events see: scripts replay any. */
            char *end;
            double now = strtod(argument, &end);
            acted = false;
            if (!*argument || *end || !(now >= 0 && now < 1e15)) fprintf(stderr, "vega: time takes milliseconds\n");
            else app.now = now;
        } else if (!strcmp(command, "tick")) {
            input = pure_module_input(app.module, argument);
            verb = "tick";
            if (input < 0 || app.module->input[input].kind != PURE_KIND_TIMER) {
                fprintf(stderr, "vega: no timer %s\n", argument);
                input = -1;
                ok = false;
            } else ok = pure_app_tick(&app, (uint32_t)input) == PURE_OK;
        } else if (!strcmp(command, "swap")) {
            acted = false;
            if (!swap(argument, read_module(argument))) fprintf(stderr, "vega: kept the running module\n");
        } else if (!strcmp(command, "frame")) {
            long count = *argument ? strtol(argument, NULL, 10) : 1;
            for (long i = 0; i < count && i < 600; ++i) ok = pure_app_frame(&app) == PURE_OK && ok;
        } else if (!strcmp(command, "show")) {
            acted = false;
            if (surface == SURFACE_CLI) vega_print(stdout, &app, &screen, color);
            else if (surface == SURFACE_SAY) vega_say(stdout, &app, &screen, true);
            else if ((shown = true) && painting) {
                Out out = {0};
                vega_draw(&grid, &app, &screen, entry, entry_length, typing);
                paint(&grid, &out);
                printf("paint %zu\n", out.used);
                fwrite(out.bytes, 1, out.used, stdout);
                putchar('\n');
                free(out.bytes);
            } else {
                vega_draw(&grid, &app, &screen, entry, entry_length, typing);
                dump(&grid);
                printf("cells %lu\n", vega_evaluations() - counted);
                char path[512];
                unsigned long differing;
                if (surface == SURFACE_PIXELS) {
                    if (!write_frame(&grid, path)) { fprintf(stderr, "vega: cannot write %s\n", path); return 1; }
                    printf("frame %s %dx%d\n", path, (int)grid.width * face.cell_width, (int)grid.height * face.cell_height);
                } else if (surface == SURFACE_DISPLAY) {
                    if (!show_frame(&grid, path, &differing)) { fputs("vega: the display did not take the frame\n", stderr); return 1; }
                    if (path[0]) printf("frame %s differing %lu grid %ux%u\n", path, differing, grid.width, grid.height);
                }
            }
            counted = vega_evaluations();
        } else {
            fprintf(stderr, "vega: unknown command %s\n", command);
            continue;
        }
        if (!ok && input >= 0) fprintf(stderr, "vega: %s failed\n", app.module->input_names[input]);
        if (surface == SURFACE_SAY && acted) {
            if (!ok) printf("Could not %s.\n", input >= 0 ? app.module->input_names[input] : verb);
            else vega_say(stdout, &app, &screen, false);
        }
        fflush(stdout);
    }
    drawn = NULL;
    vega_grid_free(&grid);
    return 0;
}

/* Surfaces that draw glyphs. */
static bool glyphed(const char *surface) { return !strcmp(surface, "pixels") || !strcmp(surface, "display"); }

/* The symbols a pixel surface draws with, read whole and kept. */
static bool open_face(const char *path, float size) {
    static VegaSymbols symbols;
    FILE *f = fopen(path, "rb");
    long length = f && !fseek(f, 0, SEEK_END) ? ftell(f) : -1;
    unsigned char *bytes = length > 0 && !fseek(f, 0, SEEK_SET) ? malloc((size_t)length) : NULL;
    bool ok = bytes && fread(bytes, 1, (size_t)length, f) == (size_t)length;
    if (f) fclose(f);
    char error[128] = "cannot read it";
    ok = ok && vega_symbols_open(&symbols, bytes, (size_t)length, error, sizeof(error));
    if (ok && !vega_face_open(&face, &symbols, size)) {
        ok = false;
        snprintf(error, sizeof(error), "no line and digit to lay a grid out with");
    }
    if (!ok) fprintf(stderr, "vega: %s: %s\n", path, error);
    return ok; /* the bytes stay: the face reads them */
}

int main(int argc, char **argv) {
    unsigned width = 0, height = 0, port = 8080;
    const char *symbols_path = NULL, *card = "/dev/dri/card1";
    float size = 16;
    bool writeback = false;
    bool dumped = false, painting = false, watch = false, usage = argc < 3;
    const char *store = NULL, *listen_on = "127.0.0.1";
    for (int i = 3; !usage && i < argc; i += 2) {
        if (!strcmp(argv[i], "--watch") && (!strcmp(argv[1], "tui") || !strcmp(argv[1], "web"))) {
            watch = true;
            --i; /* a flag without a value */
            continue;
        }
        if (i + 1 >= argc) usage = true;
        else if (!strcmp(argv[i], "--store")) store = argv[i + 1];
        else if (!strcmp(argv[i], "--listen") && !strcmp(argv[1], "web")) listen_on = argv[i + 1];
        else if (!strcmp(argv[i], "--port") && !strcmp(argv[1], "web") && sscanf(argv[i + 1], "%u", &port) == 1 &&
                 port < 65536) {}
        else if ((!strcmp(argv[i], "--dump") || !strcmp(argv[i], "--paint") ||
                  (!strcmp(argv[i], "--grid") && !strcmp(argv[1], "pixels"))) &&
                 sscanf(argv[i + 1], "%ux%u", &width, &height) == 2 && width && height && width <= 1000 && height <= 1000)
            dumped = true, painting = !strcmp(argv[i], "--paint");
        else if (!strcmp(argv[i], "--writeback") && !strcmp(argv[1], "display") &&
                 sscanf(argv[i + 1], "%ux%u", &width, &height) == 2 && width && height)
            writeback = true;
        else if (!strcmp(argv[i], "--card") && !strcmp(argv[1], "display")) card = argv[i + 1];
        else if (!strcmp(argv[i], "--symbols") && glyphed(argv[1])) symbols_path = argv[i + 1];
        else if (!strcmp(argv[i], "--out") && glyphed(argv[1])) frames_prefix = argv[i + 1];
        else if (!strcmp(argv[i], "--size") && glyphed(argv[1]) && sscanf(argv[i + 1], "%f", &size) == 1) {}
        else usage = true;
    }
    bool pixels = argc > 1 && !strcmp(argv[1], "pixels"), on_display = argc > 1 && !strcmp(argv[1], "display");
    if (usage || (dumped && strcmp(argv[1], "tui") && !pixels) || (!strcmp(argv[1], "check") && argc != 3) ||
        (pixels && (!dumped || !symbols_path || !frames_prefix)) || (on_display && (!symbols_path || (writeback && !frames_prefix)))) {
        fputs("vega tui|cli|say MODULE.pmod [--store PATH]\n"
              "vega tui MODULE.pmod [--store PATH] [--watch] | --dump|--paint WIDTHxHEIGHT < script\n"
              "vega web MODULE.pmod [--store PATH] [--listen ADDRESS] [--port N] [--watch]\n"
              "vega pixels MODULE.pmod [--store PATH] --symbols FONT.vsym [--size PX] --grid WIDTHxHEIGHT --out PREFIX < script\n"
              "vega display MODULE.pmod [--store PATH] --symbols FONT.vsym [--size PX] [--card PATH]\n"
              "             [--writeback WIDTHxHEIGHT --out PREFIX] < script\n"
              "vega check MODULE.pmod\n", stderr);
        return 2;
    }
    if ((pixels || on_display) && !open_face(symbols_path, size)) return 2;
    if (on_display) {
        char error[256];
        if (!(display = vega_display_open(card, writeback, writeback ? width : 0, writeback ? height : 0, error, sizeof(error)))) {
            fprintf(stderr, "vega: %s\n", error);
            return 2;
        }
        unsigned pixels_across, pixels_down;
        size_t stride;
        vega_display_buffer(display, &pixels_across, &pixels_down, &stride);
        width = pixels_across / (unsigned)face.cell_width;
        height = pixels_down / (unsigned)face.cell_height;
    }
    if (!strcmp(argv[1], "check")) {
        if (!load_module(argv[2], &modules[0])) return 2;
        return vega_check(&modules[0], print_finding, argv[2]) ? 1 : 0;
    }
    Surface surface = !strcmp(argv[1], "cli") ? SURFACE_CLI : !strcmp(argv[1], "say") ? SURFACE_SAY :
                      !strcmp(argv[1], "tui") ? SURFACE_TUI : !strcmp(argv[1], "web") ? SURFACE_WEB :
                      pixels ? SURFACE_PIXELS : on_display ? SURFACE_DISPLAY : (Surface)-1;
    if ((int)surface < 0) { fprintf(stderr, "vega: unknown surface %s\n", argv[1]); return 2; }
    if (!load(argv[2], store)) return 2;
    if (watch && !dumped) {
        watched = argv[2];
        watched_digest = module_digest; /* of what load read */
    }
    int status = surface == SURFACE_WEB ? vega_web(&app, &screen, listen_on, port, watched ? module_changed : NULL) :
                 surface == SURFACE_TUI && !dumped ? interactive() : script(surface, width, height, painting);
    /* Frame changes are stored with events; keep the last ones too. */
    if (pure_app_save(&app) != PURE_OK) { fputs("vega: cannot save\n", stderr); status = status ? status : 1; }
    pure_app_stop(&app);
    vega_display_close(display);
    return status;
}