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

#include "apfl.h"
#include "alloc.h"
#include "context.h"
#include "gc.h"
#include "hashmap.h"
#include "resizable.h"
#include "strings.h"
#include "value.h"

static struct stack *
stack_new(struct gc *gc)
{
    struct stack *stack = apfl_gc_new_stack(gc);
    if (stack == NULL) {
        return NULL;
    }

    *stack = (struct stack) {
        .items = NULL,
        .len = 0,
        .cap = 0,
    };

    return stack;
}

void
apfl_stack_deinit(struct apfl_allocator allocator, struct stack *stack)
{
    FREE_LIST(allocator, stack->items, stack->cap);
}

bool
apfl_stack_push(apfl_ctx ctx, struct apfl_value value)
{
    return apfl_resizable_append(
        ctx->gc.allocator,
        sizeof(struct apfl_value),
        (void **)&ctx->stack->items,
        &ctx->stack->len,
        &ctx->stack->cap,
        &value,
        1
    );
}

bool
apfl_stack_check_index(apfl_ctx ctx, apfl_stackidx *index)
{
    if (*index < 0) {
        if ((size_t)-*index > ctx->stack->len) {
            return false;
        }
        *index = ctx->stack->len + *index;
    } else if ((size_t)*index >= ctx->stack->len) {
        return false;
    }

    assert(0 <= *index && (size_t)*index < ctx->stack->len);

    return true;
}

static int
cmp_stackidx(const void *_a, const void *_b)
{
    const apfl_stackidx *a = _a;
    const apfl_stackidx *b = _b;
    return *a - *b;
}

bool apfl_stack_drop_multi(apfl_ctx ctx, size_t count, apfl_stackidx *indices)
{
    for (size_t i = 0; i < count; i++) {
        if (!apfl_stack_check_index(ctx, &indices[i])) {
            return false;
        }
    }

    qsort(indices, count, sizeof(apfl_stackidx), cmp_stackidx);

    for (size_t i = count; i-- > 0; ) {
        // Will not fail, as we've already checked the indices
        assert(apfl_resizable_cut_without_resize(
            sizeof(struct apfl_value),
            (void **)&ctx->stack->items,
            &ctx->stack->len,
            indices[i],
            1
        ));
    }

    // TODO: Shrink stack

    return true;
}

bool
apfl_stack_pop(apfl_ctx ctx, struct apfl_value *value, apfl_stackidx index)
{
    if (!apfl_stack_check_index(ctx, &index)) {
        return false;
    }

    *value = ctx->stack->items[index];

    assert(apfl_resizable_splice(
        ctx->gc.allocator,
        sizeof(struct apfl_value),
        (void **)ctx->stack,
        &ctx->stack->len,
        &ctx->stack->cap,
        index,
        1,
        NULL,
        0
    ));

    return true;
}

static struct apfl_value *
stack_get_pointer(apfl_ctx ctx, apfl_stackidx index)
{
    if (!apfl_stack_check_index(ctx, &index)) {
        return NULL;
    }

    return &ctx->stack->items[index];
}

static bool
stack_get_and_adjust_index(apfl_ctx ctx, struct apfl_value *value, apfl_stackidx *index)
{
    if (!apfl_stack_check_index(ctx, index)) {
        return false;
    }

    *value = ctx->stack->items[*index];

    return true;
}

bool
apfl_stack_get(apfl_ctx ctx, struct apfl_value *value, apfl_stackidx index)
{
    return stack_get_and_adjust_index(ctx, value, &index);
}

struct apfl_value *
apfl_stack_push_placeholder(apfl_ctx ctx)
{
    if (!apfl_stack_push(ctx, (struct apfl_value) {.type = VALUE_NIL})) {
        return NULL;
    }

    return stack_get_pointer(ctx, -1);
}

bool
apfl_stack_drop(apfl_ctx ctx, apfl_stackidx index)
{
    struct apfl_value value;
    return apfl_stack_pop(ctx, &value, index);
}

void
apfl_stack_clear(apfl_ctx ctx)
{
    ctx->stack->len = 0;
}

apfl_ctx
apfl_ctx_new(struct apfl_allocator base_allocator)
{
    apfl_ctx ctx = ALLOC_OBJ(base_allocator, struct apfl_ctx_data);
    if (ctx == NULL) {
        return NULL;
    }

    if (!apfl_gc_init(&ctx->gc, base_allocator)) {
        FREE_OBJ(base_allocator, ctx);
        return NULL;
    }

    if ((ctx->scope = apfl_scope_new(&ctx->gc)) == NULL) {
        goto error;
    }

    if (!apfl_gc_root_add(&ctx->gc, GC_OBJECT_FROM(ctx->scope, GC_TYPE_SCOPE))) {
        goto error;
    }

    if ((ctx->stack = stack_new(&ctx->gc)) == NULL) {
        goto error;
    }

    if (!apfl_gc_root_add(&ctx->gc, GC_OBJECT_FROM(ctx->stack, GC_TYPE_STACK))) {
        goto error;
    }

    return ctx;

error:
    apfl_ctx_destroy(ctx);
    return NULL;
}

void
apfl_ctx_destroy(apfl_ctx ctx)
{
    if (ctx == NULL) {
        return;
    }

    struct apfl_allocator base_allocator = ctx->gc.base_allocator;

    apfl_gc_full(&ctx->gc);
    apfl_gc_deinit(&ctx->gc);

    FREE_OBJ(base_allocator, ctx);
}

#define CREATE_GC_OBJECT_VALUE_ON_STACK(ctx, TYPE, MEMB, NEW)    \
    struct apfl_value *value = apfl_stack_push_placeholder(ctx); \
    if (value == NULL) {                                         \
        return APFL_RESULT_ERR_FATAL;                            \
    }                                                            \
                                                                 \
    struct apfl_value new_value = {.type = TYPE};                \
    if ((new_value.MEMB = NEW) == NULL) {                        \
        assert(apfl_stack_drop(ctx, -1));                        \
        return APFL_RESULT_ERR_FATAL;                            \
    }                                                            \
                                                                 \
    *value = new_value;                                          \
                                                                 \
    return APFL_RESULT_OK;

enum apfl_result
apfl_push_nil(apfl_ctx ctx)
{
    return apfl_stack_push(ctx, (struct apfl_value) {
        .type = VALUE_NIL,
    }) ? APFL_RESULT_OK : APFL_RESULT_ERR;
}

enum apfl_result
apfl_push_bool(apfl_ctx ctx, bool b)
{
    return apfl_stack_push(ctx, (struct apfl_value) {
        .type = VALUE_BOOLEAN,
        .boolean = b,
    }) ? APFL_RESULT_OK : APFL_RESULT_ERR;
}

enum apfl_result
apfl_push_number(apfl_ctx ctx, apfl_number num)
{
    return apfl_stack_push(ctx, (struct apfl_value) {
        .type = VALUE_NUMBER,
        .number = num,
    }) ? APFL_RESULT_OK : APFL_RESULT_ERR;
}

static struct apfl_string *
new_copied_string(struct gc *gc, struct apfl_string_view sv)
{
    struct apfl_string s = apfl_string_blank();
    if (!apfl_string_copy(gc->allocator, &s, sv)) {
        return NULL;
    }

    struct apfl_string *out = apfl_string_move_into_new_gc_string(gc, &s);
    if (out == NULL) {
        apfl_string_deinit(gc->allocator, &s);
        return NULL;
    }

    return out;
}

enum apfl_result
apfl_push_string_view_copy(apfl_ctx ctx, struct apfl_string_view sv)
{
    CREATE_GC_OBJECT_VALUE_ON_STACK(
        ctx,
        VALUE_STRING,
        string,
        new_copied_string(&ctx->gc, sv)
    )
}

enum apfl_result
apfl_push_const_string(apfl_ctx ctx, const char *string)
{
    return apfl_stack_push(ctx, (struct apfl_value) {
        .type = VALUE_CONST_STRING,
        .const_string = apfl_string_view_from(string),
    }) ? APFL_RESULT_OK : APFL_RESULT_ERR_FATAL;
}

enum apfl_result
apfl_list_create(apfl_ctx ctx, size_t initial_cap)
{
    CREATE_GC_OBJECT_VALUE_ON_STACK(
        ctx,
        VALUE_LIST,
        list,
        apfl_list_new(&ctx->gc, initial_cap)
    )
}

enum apfl_result
apfl_list_append(apfl_ctx ctx, apfl_stackidx list_index, apfl_stackidx value_index)
{
    struct apfl_value *list_val = stack_get_pointer(ctx, list_index);
    if (list_val == NULL) {
        return APFL_RESULT_ERR;
    }

    if (list_val->type != VALUE_LIST) {
        return APFL_RESULT_ERR;
    }

    struct apfl_value value;
    if (!apfl_stack_get(ctx, &value, value_index)) {
        return APFL_RESULT_ERR;
    }

    enum apfl_result result = apfl_list_splice(
        &ctx->gc,
        &list_val->list,
        list_val->list->len,
        0,
        &value,
        1
    )
        ? APFL_RESULT_OK
        : APFL_RESULT_ERR;

    assert(apfl_stack_drop(ctx, value_index));

    return result;
}

enum apfl_result
apfl_list_append_list(apfl_ctx ctx, apfl_stackidx dst_index, apfl_stackidx src_index)
{
    struct apfl_value *dst_val = stack_get_pointer(ctx, dst_index);
    if (dst_val == NULL) {
        return APFL_RESULT_ERR;
    }

    if (dst_val->type != VALUE_LIST) {
        return APFL_RESULT_ERR;
    }

    struct apfl_value src_val;
    if (!apfl_stack_get(ctx, &src_val, src_index)) {
        return APFL_RESULT_ERR;
    }

    if (src_val.type != VALUE_LIST) {
        assert(apfl_stack_drop(ctx, src_index));
        return APFL_RESULT_ERR;
    }

    enum apfl_result result = apfl_list_splice(
        &ctx->gc,
        &dst_val->list,
        dst_val->list->len,
        0,
        src_val.list->items,
        src_val.list->len
    )
        ? APFL_RESULT_OK
        : APFL_RESULT_ERR;

    assert(apfl_stack_drop(ctx, src_index));
    return result;
}

enum apfl_result
apfl_dict_create(apfl_ctx ctx)
{
    CREATE_GC_OBJECT_VALUE_ON_STACK(
        ctx,
        VALUE_DICT,
        dict,
        apfl_dict_new(&ctx->gc)
    )
}

enum apfl_result
apfl_dict_set(
    apfl_ctx ctx,
    apfl_stackidx dict_index,
    apfl_stackidx k_index,
    apfl_stackidx v_index
) {
    struct apfl_value k;
    struct apfl_value v;
    struct apfl_value *dict_value;

    if (
        !apfl_stack_get(ctx, &k, k_index)
        || !apfl_stack_get(ctx, &v, v_index)
        || (dict_value = stack_get_pointer(ctx, dict_index)) == NULL
    ) {
        return APFL_RESULT_ERR;
    }

    if (dict_value->type != VALUE_DICT) {
        assert(apfl_stack_drop_multi(ctx, 2, (apfl_stackidx[]){k_index, v_index}));
        return APFL_RESULT_ERR;
    }

    if (!apfl_dict_set_raw(&ctx->gc, &dict_value->dict, k, v)) {
        assert(apfl_stack_drop_multi(ctx, 2, (apfl_stackidx[]){k_index, v_index}));
        return APFL_RESULT_ERR;
    }

    assert(apfl_stack_drop_multi(ctx, 2, (apfl_stackidx[]){k_index, v_index}));
    return APFL_RESULT_OK;
}

static enum apfl_result
apfl_get_member_inner(
    apfl_ctx ctx,
    struct apfl_value container,
    struct apfl_value k
) {
    struct apfl_value *value = apfl_stack_push_placeholder(ctx);
    if (value == NULL) {
        return APFL_RESULT_ERR;
    }

    if (apfl_value_get_item(container, k, value) != GET_ITEM_OK) {
        assert(apfl_stack_drop(ctx, -1));
        return APFL_RESULT_ERR;
    }

    return APFL_RESULT_OK;
}

enum apfl_result
apfl_get_member(
    apfl_ctx ctx,
    apfl_stackidx container_index,
    apfl_stackidx k_index
) {
    struct apfl_value container;
    struct apfl_value k;
    if (
        !stack_get_and_adjust_index(ctx, &container, &container_index)
        || !stack_get_and_adjust_index(ctx, &k, &k_index)
    ) {
        return APFL_RESULT_ERR;
    }

    enum apfl_result result = apfl_get_member_inner(ctx, container, k);
    assert(apfl_stack_drop_multi(ctx, 2, (apfl_stackidx[]){k_index, container_index}));
    return result;
}

void
apfl_gc_stack_traverse(struct stack *stack, gc_visitor visitor, void *opaque)
{
    for (size_t i = 0; i < stack->len; i++) {
        struct gc_object *object = apfl_value_get_gc_object(stack->items[i]);
        if (object != NULL) {
            visitor(opaque, object);
        }
    }
}