/*
 * test_ha_start_election_async.c — Unity tests for task 2.4:
 * ha_start_election_async() non-blocking election initiator.
 *
 * Strategy:
 *   - n_peers=1 shortcircuit: no iomgr needed; election completes synchronously
 *     immediately after ha_start_election_async returns.  The single-node
 *     shortcircuit delegates to raft_start_election, which fires on_become_leader
 *     synchronously → raft_cb_become_leader (ha-single-leader-role task 2.2),
 *     so the role lands DIRECTLY in CTRL_PRIMARY — there is no transitional
 *     leader sub-state and no wall-clock promotion watchdog (Req 1.1, 1.5).
 *   - Function returns in < 5ms (observable via clock_gettime).
 *   - n_peers=1 shortcircuit stores n_peers in ha->n_peers.
 *
 * Observable: function returns in < 5ms; n_peers stored; shortcircuit fires
 * ha_elect_evaluate_and_signal directly (no iomgr/delaymgr needed for n_peers=1).
 *
 * Requirements: 1.3 (non-blocking), 2.1 (single-node shortcircuit), 2.4 (vote send)
 * Boundary: ha.c (election orchestration)
 */
#define _GNU_SOURCE
#include <errno.h>
#include <stdatomic.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <unity/unity.h>

#include "ha.h"
#include "netio.h"
#include "xce/cluster_def.h"
#include "delay.h"

/* Forward declaration for function under test */
extern void ha_start_election_async(ha_state_t *ha, cluster_t *c,
                                    int n_peers, xce_candidate_t **peers,
                                    uint64_t my_config_tag, uint64_t my_lsn,
                                    const char *my_name);

/* ── Minimal ha_config_t for tests ─────────────────────────────────────── */

static ha_config_t g_async_cfg = {
    .heartbeat_interval_ms     = 3000,
    .heartbeat_timeout_ms      = 10000,
    .election_timeout_ms       = 2000,
    .probe_connect_timeout_ms  = 500,
    .max_promotion_retries     = 5,
    .election_jitter_max_ms    = 0,
    .election_priority_step_ms = 500,
};

/* ── Helper: elapsed ms since a timespec ───────────────────────────────── */

static long elapsed_ms(const struct timespec *start)
{
    struct timespec now;
    clock_gettime(CLOCK_MONOTONIC, &now);
    long sec_diff  = (long)(now.tv_sec  - start->tv_sec);
    long nsec_diff = (long)(now.tv_nsec - start->tv_nsec);
    return sec_diff * 1000L + nsec_diff / 1000000L;
}

/* ── Test 1: single-node shortcircuit returns in < 5ms ──────────────────── */

static void test_single_node_returns_quickly(void)
{
    ha_state_t ha;
    ha_init(&ha, &g_async_cfg, 0);
    ha.phase2_done = 0; /* first boot */

    /* n_peers=1: shortcircuit, no iomgr or delaymgr needed */
    struct timespec t0;
    clock_gettime(CLOCK_MONOTONIC, &t0);

    ha_start_election_async(&ha, NULL, 1, NULL, 100ULL, 50ULL, "ctrl-a");

    long ms = elapsed_ms(&t0);
    TEST_ASSERT_LESS_OR_EQUAL_INT_MESSAGE(5, (int)ms,
        "ha_start_election_async(n_peers=1) must return in < 5ms");

    ha_fini(&ha);
    printf("test_single_node_returns_quickly: PASS (elapsed=%ldms)\n", ms);
}

/* ── Test 2: single-node shortcircuit stores n_peers in ha->n_peers ──────── */

static void test_single_node_stores_n_peers(void)
{
    ha_state_t ha;
    ha_init(&ha, &g_async_cfg, 0);
    ha.n_peers = 0;

    ha_start_election_async(&ha, NULL, 1, NULL, 0ULL, 0ULL, "ctrl-a");

    TEST_ASSERT_EQUAL_INT_MESSAGE(1, ha.n_peers,
        "ha->n_peers must be set to n_peers argument (1 for single-node)");

    ha_fini(&ha);
    printf("test_single_node_stores_n_peers: PASS\n");
}

/* ── Test 3: single-node shortcircuit enters CTRL_PRIMARY directly ───────── */

static void test_single_node_shortcircuit_evaluates_immediately(void)
{
    ha_state_t ha;
    ha_init(&ha, &g_async_cfg, 0);
    ha.phase2_done = 0;
    /* Start in CTRL_ELECTING state so role transition is visible */
    atomic_store_explicit(&ha.role, (int32_t)CTRL_ELECTING, memory_order_release);

    /* n_peers=1: the shortcircuit fires raft_start_election → on_become_leader
     * (raft_cb_become_leader) synchronously.  ha-single-leader-role (Req 1.1):
     * a winning node lands DIRECTLY in CTRL_PRIMARY — there is no transitional
     * leader sub-state.  New-leader safety comes from the own-term
     * WAL_NOOP + writable_lsn gate, not from a fourth role value. */
    ha_start_election_async(&ha, NULL, 1, NULL, 100ULL, 50ULL, "ctrl-a");

    ctrl_role_t role = (ctrl_role_t)atomic_load_explicit(&ha.role, memory_order_acquire);
    TEST_ASSERT_EQUAL_INT_MESSAGE((int)CTRL_PRIMARY, (int)role,
        "single-node shortcircuit must enter CTRL_PRIMARY directly (Req 1.1) — "
        "no transitional leader sub-state");

    ha_fini(&ha);
    printf("test_single_node_shortcircuit_evaluates_immediately: PASS (role=%d == CTRL_PRIMARY)\n",
           (int)role);
}

/* ── Test 6: single-node shortcircuit lands directly in CTRL_PRIMARY ──────── */

static void test_single_node_not_primary_directly(void)
{
    ha_state_t ha;
    ha_init(&ha, &g_async_cfg, 0);

    ha_start_election_async(&ha, NULL, 1, NULL, 0ULL, 0ULL, "ctrl-a");

    /* ha-single-leader-role (Req 1.1): the winning node lands in CTRL_PRIMARY
     * immediately — the old "must go through a transitional state first"
     * contract is gone.  Promotion arms NO wall-clock watchdog (Req 1.5); the
     * own-term gate (WAL_NOOP + writable_lsn) provides new-leader safety. */
    ctrl_role_t role = (ctrl_role_t)atomic_load_explicit(&ha.role, memory_order_acquire);
    TEST_ASSERT_EQUAL_INT_MESSAGE((int)CTRL_PRIMARY, (int)role,
        "single-node shortcircuit must land DIRECTLY in CTRL_PRIMARY (Req 1.1) — "
        "no transitional leader sub-state, no wall-clock watchdog (Req 1.5)");

    ha_fini(&ha);
    printf("test_single_node_not_primary_directly: PASS (role=%d == CTRL_PRIMARY)\n", (int)role);
}

/* ── Test 4: ha->n_peers set for multi-peer count too ───────────────────── */

static void test_n_peers_stored_for_multi_peer(void)
{
    /* We can't test actual multi-peer endpoint setup without iomgr,
     * but we can verify n_peers is stored correctly for any value.
     * Pass peers=NULL to avoid actual connect attempts; the function
     * should skip peer on connect failure (design spec). */
    ha_state_t ha;
    ha_init(&ha, &g_async_cfg, 0);
    ha.n_peers = 0;

    /* Passing n_peers=3 with peers=NULL: each peer would fail connect,
     * but n_peers must be stored before attempting connects. */
    ha_start_election_async(&ha, NULL, 3, NULL, 100ULL, 50ULL, "ctrl-a");

    TEST_ASSERT_EQUAL_INT_MESSAGE(3, ha.n_peers,
        "ha->n_peers must be set to n_peers argument even for multi-peer");

    ha_fini(&ha);
    printf("test_n_peers_stored_for_multi_peer: PASS\n");
}

/* ── Test 5: single-node election increments term ───────────────────────── */

static void test_single_node_increments_term(void)
{
    ha_state_t ha;
    ha_init(&ha, &g_async_cfg, 0);
    uint64_t initial_term = atomic_load_explicit(&ha.term, memory_order_acquire);

    ha_start_election_async(&ha, NULL, 1, NULL, 0ULL, 0ULL, "ctrl-a");

    uint64_t final_term = atomic_load_explicit(&ha.term, memory_order_acquire);
    TEST_ASSERT_GREATER_THAN_UINT64_MESSAGE(initial_term, final_term,
        "single-node election must increment ha->term");

    ha_fini(&ha);
    printf("test_single_node_increments_term: PASS (term: %"PRIu64" → %"PRIu64")\n",
           initial_term, final_term);
}

/* ── Suite entry point ───────────────────────────────────────────────────── */

void test_ha_start_election_async(void)
{
    RUN_TEST(test_single_node_returns_quickly);
    RUN_TEST(test_single_node_stores_n_peers);
    RUN_TEST(test_single_node_shortcircuit_evaluates_immediately);
    RUN_TEST(test_single_node_not_primary_directly);
    RUN_TEST(test_n_peers_stored_for_multi_peer);
    RUN_TEST(test_single_node_increments_term);
}