/*
 * test_alloc_plan_iter.c - contract test for the lazy allocation-plan and
 * host-candidate iterator interfaces (scheduler-allocation spec, task
 * 1.1, Req 2 AC 1 / Req 3 AC 1).
 *
 * This task only adds a header (sched/alloc_iter.h) declaring
 * xce_alloc_plan_t/xce_alloc_plan_iter_t/xce_host_iter_t -- no allocator
 * is wired onto them yet (parjob_allocator/seqjob_allocator rewrap is
 * later tasks' work). So the RED/GREEN evidence for this task is:
 *
 *   RED:   before sched/alloc_iter.h existed, this file failed to compile
 *          (unknown types xce_alloc_plan_t/xce_alloc_plan_iter_t/
 *          xce_host_iter_t).
 *   GREEN: with the header in place, a trivial, no-op reference
 *          implementation of each interface (below) can be constructed,
 *          stack-allocated and initialized in place per the documented
 *          convention, and driven through a full init()/next()/fini()
 *          cycle -- including the exact plan -> per-bucket host_iter
 *          composition shape requirements.md's Composition Algorithm
 *          describes -- proving the contract shape actually compiles and
 *          is usable, not just that a struct literal type-checks.
 *
 * Both stub implementations ignore the real xce_primary_resreq_t/
 * xce_sched_core_t/plan/workers arguments (ok, per the header's own
 * "each concrete plan-iterator implementation carries whatever it needs"
 * note) and always yield exactly one candidate before signaling stable
 * exhaustion.
 */
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>

#include <unity/unity.h>

#include "sched/alloc_iter.h"

/* ---- trivial no-op xce_alloc_plan_iter_t reference implementation ---- */

typedef struct {
    int              served; /* 0 = not yet served, 1 = exhausted */
    int              bucket_slots[1];
    xce_alloc_plan_t plan;
} stub_plan_priv_t;

static int stub_plan_iter_init(xce_alloc_plan_iter_t* iter,
                               xce_primary_resreq_t*  resreq,
                               xce_sched_core_t*      core)
{
    stub_plan_priv_t* priv;

    /* Stub: ignores the real resreq/core state -- a real implementation
     * (parjob's combinatorial one, seqjob's trivial one) would derive its
     * plan space from resreq->maxTasks here. */
    (void)resreq;
    (void)core;

    if (iter == NULL) {
        return -EINVAL;
    }

    priv = (stub_plan_priv_t*)calloc(1, sizeof(*priv));
    if (priv == NULL) {
        return -ENOMEM;
    }

    priv->served            = 0;
    priv->bucket_slots[0]   = 1;
    priv->plan.nbuckets     = 1;
    priv->plan.bucket_slots = priv->bucket_slots;

    iter->private = priv;

    return 0;
}

static xce_alloc_plan_t* stub_plan_iter_next(xce_alloc_plan_iter_t* iter)
{
    stub_plan_priv_t* priv;

    /* Req 2 AC 6: a real cancellation point at least once per invocation
     * -- combinatorial generation has none of its own. */
    pthread_testcancel();

    if (iter == NULL) {
        return NULL;
    }

    priv = (stub_plan_priv_t*)iter->private;
    if (priv == NULL || priv->served) {
        return NULL; /* Req 2 AC 4: stable exhaustion signal */
    }

    priv->served = 1;

    return &priv->plan;
}

static void stub_plan_iter_fini(xce_alloc_plan_iter_t* iter)
{
    if (iter == NULL) {
        return;
    }

    free(iter->private);
    iter->private = NULL;
}

/* ---- trivial no-op xce_host_iter_t reference implementation ---- */

typedef struct {
    int                served; /* 0 = not yet served, 1 = exhausted */
    xce_sched_worker_t worker;
} stub_host_priv_t;

static int stub_host_iter_init(xce_host_iter_t* iter, xce_alloc_plan_t* plan,
                               var workers)
{
    stub_host_priv_t* priv;

    /* Stub: ignores the real plan/workers state -- the one shared real
     * implementation (host_iter.c, Req 3) would filter `workers` by
     * plan's select expression + slot availability here. */
    (void)plan;
    (void)workers;

    if (iter == NULL) {
        return -EINVAL;
    }

    priv = (stub_host_priv_t*)calloc(1, sizeof(*priv));
    if (priv == NULL) {
        return -ENOMEM;
    }

    priv->served      = 0;
    priv->worker.name = "stub-host";

    iter->private = priv;

    return 0;
}

static xce_sched_worker_t* stub_host_iter_next(xce_host_iter_t* iter)
{
    stub_host_priv_t* priv;

    /* Req 3 AC 6: a real cancellation point at least once per invocation
     * -- scanning/filtering has none of its own. */
    pthread_testcancel();

    if (iter == NULL) {
        return NULL;
    }

    priv = (stub_host_priv_t*)iter->private;
    if (priv == NULL || priv->served) {
        return NULL; /* Req 3 AC 3: exhausted for this instance */
    }

    priv->served = 1;

    return &priv->worker;
}

static void stub_host_iter_fini(xce_host_iter_t* iter)
{
    if (iter == NULL) {
        return;
    }

    free(iter->private);
    iter->private = NULL;
}

void setUp(void) { return; }
void tearDown(void) { return; }

/*
 * Req 2 AC 1/2/4/5: the plan iterator is stack-allocated by the caller
 * and initialized in place (not a heap-allocating factory -- see the
 * header's own convention note), yields exactly one plan, then a stable
 * NULL on every subsequent next() call, and fini() releases it cleanly.
 */
static void test_plan_iter_stub_produces_one_plan_then_stable_null(void)
{
    xce_alloc_plan_iter_t  iter_storage;
    xce_alloc_plan_iter_t* iter = &iter_storage;
    xce_alloc_plan_t*      plan;

    memset(iter, 0, sizeof(*iter));
    iter->init = stub_plan_iter_init;
    iter->next = stub_plan_iter_next;
    iter->fini = stub_plan_iter_fini;

    TEST_ASSERT_EQUAL_INT(0, iter->init(iter, NULL, NULL));

    plan = iter->next(iter);
    TEST_ASSERT_NOT_NULL(plan);
    TEST_ASSERT_EQUAL_INT(1, plan->nbuckets);
    TEST_ASSERT_NOT_NULL(plan->bucket_slots);
    TEST_ASSERT_EQUAL_INT(1, plan->bucket_slots[0]);

    /* Req 2 AC 4: end-of-iteration signal, stable across repeated calls. */
    TEST_ASSERT_NULL(iter->next(iter));
    TEST_ASSERT_NULL(iter->next(iter));

    iter->fini(iter);
    TEST_ASSERT_NULL(iter->private);
}

/*
 * Req 3 AC 1/2/3/5: the host iterator is likewise stack-allocated and
 * initialized in place from a plan, yields exactly one candidate host,
 * then a stable NULL, and fini() is independent of the owning plan
 * iterator's own lifecycle -- proved by finiing the host iterator first
 * and then confirming plan_iter's own exhaustion/fini() sequence is
 * completely unaffected.
 */
static void test_host_iter_stub_produces_one_worker_then_stable_null(void)
{
    xce_alloc_plan_iter_t  plan_iter_storage;
    xce_alloc_plan_iter_t* plan_iter = &plan_iter_storage;
    xce_alloc_plan_t*      plan;
    xce_host_iter_t        host_iter_storage;
    xce_host_iter_t*       host_iter = &host_iter_storage;
    xce_sched_worker_t*    w;

    memset(plan_iter, 0, sizeof(*plan_iter));
    plan_iter->init = stub_plan_iter_init;
    plan_iter->next = stub_plan_iter_next;
    plan_iter->fini = stub_plan_iter_fini;

    TEST_ASSERT_EQUAL_INT(0, plan_iter->init(plan_iter, NULL, NULL));
    plan = plan_iter->next(plan_iter);
    TEST_ASSERT_NOT_NULL(plan);

    memset(host_iter, 0, sizeof(*host_iter));
    host_iter->init = stub_host_iter_init;
    host_iter->next = stub_host_iter_next;
    host_iter->fini = stub_host_iter_fini;

    /* `plan` is still valid here -- neither next() nor fini() has been
     * called again on plan_iter since it was returned above, per the
     * header's own "valid until the next next()/fini() call" contract. */
    TEST_ASSERT_EQUAL_INT(0, host_iter->init(host_iter, plan, NULL));

    w = host_iter->next(host_iter);
    TEST_ASSERT_NOT_NULL(w);
    TEST_ASSERT_EQUAL_STRING("stub-host", w->name);

    /* Req 3 AC 3: exhausted for this instance's bucket search, stable. */
    TEST_ASSERT_NULL(host_iter->next(host_iter));
    TEST_ASSERT_NULL(host_iter->next(host_iter));

    /* Req 3 AC 5: fini() on host_iter is independent of plan_iter's own
     * lifecycle -- finiing it here must not disturb plan_iter, which is
     * still fini()'d separately, afterward, below. */
    host_iter->fini(host_iter);
    TEST_ASSERT_NULL(host_iter->private);

    /* plan_iter is unaffected by host_iter->fini() -- still stably
     * exhausted (it already served its one plan above). Only now is its
     * own storage (and the `plan` pointer into it) released. */
    TEST_ASSERT_NULL(plan_iter->next(plan_iter));
    plan_iter->fini(plan_iter);
    TEST_ASSERT_NULL(plan_iter->private);
}

/*
 * Req 3 AC 4 / Req 4 AC 2 composition shape: a fresh xce_host_iter_t
 * instance is constructed from the SAME plan once per bucket, each a
 * fully independent instance -- the exact plan -> bucket -> host_iter
 * nesting requirements.md's Composition Algorithm pseudocode describes
 * for allocate_primary(), exercised here end to end against the stub
 * implementations (a 2-bucket plan, each bucket getting its own fresh
 * host_iter instance that is init()'d and fini()'d independently).
 */
static void test_fresh_host_iter_per_bucket_composes_with_one_plan(void)
{
    int              bucket_slots[2] = { 2, 1 };
    xce_alloc_plan_t two_bucket_plan
        = { .nbuckets = 2, .bucket_slots = bucket_slots };
    int b;

    for (b = 0; b < two_bucket_plan.nbuckets; b++) {
        xce_host_iter_t     host_iter_storage;
        xce_host_iter_t*    host_iter = &host_iter_storage;
        xce_sched_worker_t* w;

        memset(host_iter, 0, sizeof(*host_iter));
        host_iter->init = stub_host_iter_init;
        host_iter->next = stub_host_iter_next;
        host_iter->fini = stub_host_iter_fini;

        /* A brand-new init() per bucket -- never one instance reused
         * across the loop (Req 3's "fresh per bucket" requirement). */
        TEST_ASSERT_EQUAL_INT(
            0, host_iter->init(host_iter, &two_bucket_plan, NULL));

        w = host_iter->next(host_iter);
        TEST_ASSERT_NOT_NULL(w);

        host_iter->fini(host_iter);
        TEST_ASSERT_NULL(host_iter->private);
    }
}

int main(void)
{
    UNITY_BEGIN();
    RUN_TEST(test_plan_iter_stub_produces_one_plan_then_stable_null);
    RUN_TEST(test_host_iter_stub_produces_one_worker_then_stable_null);
    RUN_TEST(test_fresh_host_iter_per_bucket_composes_with_one_plan);
    return UNITY_END();
}