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+#ifndef PURE_DELIVER_H
+#define PURE_DELIVER_H
+#include "module.h"
+
+/* Delivering an app's saved sends over HTTP (docs/research/083-delivery-over-http.md).
+ * A wire takes one output's sends in order: each goes as a JSON object of
+ * its fields (groups as objects inside) by POST to a URL, with the headers
+ * X-Pure-Source (the sender's name for the output), X-Pure-Sequence and
+ * Idempotency-Key, one at a time, again and again until it is delivered:
+ * a 2xx answer, or a Pure receiver's refusal (a 4xx with X-Pure-Error
+ * naming a fault: it heard the message and refused it). 408, 429, 5xx and
+ * no answer are tried again after a pause (0.1 s doubling to 10 s); another
+ * 4xx is logged and tried again every 10 s. Nothing is ever dropped: what is
+ * not delivered stays in the app's outbox, and a receiver applies a number
+ * once, so a send delivered twice (its answer lost) is harmless. */
+typedef struct PureWire PureWire;
+
+/* A wire for the output named output of m to url (http[s]://host[:port]/path),
+ * as source; NULL with why in error when it cannot be. An https receiver's
+ * certificate must be trusted (the system's CAs, or the file given to
+ * pure_wire_trust before the first https wire) and name its host. */
+void pure_wire_trust(const char *ca_file);
+PureWire *pure_wire_open(const PureModule *m, const char *output, const char *url, const char *source,
+                         char *error, size_t size);
+uint32_t pure_wire_output(const PureWire *);
+/* The owner's side: queue a saved send numbered after the last queued one
+ * (it is encoded now); false when it cannot be (a bytes field that is not
+ * UTF-8 has no JSON form), and the wire then stops at it. */
+bool pure_wire_queue(PureWire *, uint64_t seq, PureSpan payload);
+uint64_t pure_wire_queued(const PureWire *);
+/* The last number delivered; any thread. */
+uint64_t pure_wire_delivered(PureWire *);
+/* Deliver on a thread of the wire's own, calling notify after each delivery. */
+bool pure_wire_start(PureWire *, void (*notify)(void *), void *context);
+/* Stop (a delivery under way is finished or abandoned) and free. */
+void pure_wire_close(PureWire *);
+/* Answers as events: the final answer to each send (a 2xx, or a 4xx but 408
+ * and 429) becomes a message event of input (a message without a key), in
+ * the order sent: its fields come from the answer's JSON object by name
+ * (other members are skipped), a field the answer lacks from the send's
+ * field of that name and type (as a request's id), and a u32 field named
+ * http_status is the answer's status. An answer that makes no message is
+ * logged and the send tried again every 10 s. Answers go one per request. */
+bool pure_wire_reply(PureWire *, uint32_t input, char *error, size_t size);
+/* The owner's side: the next answer in order, or false. Taking it counts
+ * its send delivered (the owner applies the answer, then trims); what out
+ * points to is the wire's until the next call. The answer is applied with
+ * pure_app_deliver from the wire's source with the send's number, so an
+ * answer that comes again after a restart is applied once. */
+typedef struct {
+    uint32_t input;
+    uint64_t seq;
+    PureSpan payload;
+    const uint32_t *placed;
+    const char *source;
+} PureWireAnswer;
+bool pure_wire_answer(PureWire *, PureWireAnswer *out);
+/* Counts for a host's report. */
+void pure_wire_counts(PureWire *, uint64_t *delivered, uint64_t *attempts);
+#endif