/*
 * C delivery implementation for the c-test platform.
 *
 * Provides a simple fixed-size queue and a delivery callback. The queue acts
 * as the outbox for a client: every outbound envelope is pushed here; the test
 * (orchestrated from Rust) pops envelopes and routes them to the receiving
 * client via client_push_inbound.
 *
 * This file has NO dependencies on the client-ffi or libchat Rust crates.
 */

#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

/* ------------------------------------------------------------------
 * Queue implementation
 * ------------------------------------------------------------------ */

#define MAX_ENVELOPES    64
#define MAX_ENVELOPE_SZ  32768

typedef struct {
    uint8_t data[MAX_ENVELOPE_SZ];
    size_t  len;
} Envelope;

typedef struct Queue {
    Envelope items[MAX_ENVELOPES];
    int      head;
    int      tail;
    int      count;
} Queue;

Queue *c_queue_new(void)
{
    Queue *q = (Queue *)calloc(1, sizeof(Queue));
    assert(q && "out of memory");
    return q;
}

void c_queue_free(Queue *q)
{
    free(q);
}

/**
 * Pop the oldest envelope from the queue.
 *
 * @param q        Queue to pop from.
 * @param data_out Set to a pointer into the queue's internal buffer.
 *                 Valid only until the next push or free.
 * @param len_out  Set to the envelope length in bytes.
 * @return         1 if an envelope was available, 0 if the queue was empty.
 */
int c_queue_pop(Queue *q, const uint8_t **data_out, size_t *len_out)
{
    if (q->count == 0) return 0;
    *data_out = q->items[q->head].data;
    *len_out  = q->items[q->head].len;
    q->head   = (q->head + 1) % MAX_ENVELOPES;
    q->count--;
    return 1;
}

/* ------------------------------------------------------------------
 * Delivery callback
 *
 * `userdata` must be a Queue* for the sending client's outbox.
 * ------------------------------------------------------------------ */

int32_t c_deliver_cb(
    const uint8_t *addr_ptr, size_t addr_len,
    const uint8_t *data_ptr, size_t data_len,
    void          *userdata)
{
    (void)addr_ptr; (void)addr_len; /* routing is done externally */
    Queue *q = (Queue *)userdata;
    assert(q->count < MAX_ENVELOPES && "delivery queue overflow");
    assert(data_len <= MAX_ENVELOPE_SZ && "envelope too large for queue");
    memcpy(q->items[q->tail].data, data_ptr, data_len);
    q->items[q->tail].len = data_len;
    q->tail  = (q->tail + 1) % MAX_ENVELOPES;
    q->count++;
    return 0;
}