#include <assert.h>

#include "apfl.h"
#include "internal.h"
#include "resizable.h"

struct apfl_ctx_data {
    char nothing_here_yet;
};

static struct apfl_result evaluate(apfl_ctx, struct apfl_expr *);

apfl_ctx
apfl_ctx_new()
{
    apfl_ctx ctx = ALLOC(struct apfl_ctx_data);
    if (ctx == NULL) {
        return NULL;
    }

    return ctx;
}

void
apfl_ctx_destroy(apfl_ctx ctx)
{
    free(ctx);
}

static struct apfl_value
evaluate_constant(struct apfl_expr_const *constant)
{
    struct apfl_refcounted_string *rcstring;

    switch (constant->type) {
    case APFL_EXPR_CONST_NIL:
        return (struct apfl_value) {
            .type = APFL_VALUE_NIL,
        };
    case APFL_EXPR_CONST_BOOLEAN:
        return (struct apfl_value) {
            .type = APFL_VALUE_BOOLEAN,
            .boolean = constant->boolean,
        };
    case APFL_EXPR_CONST_STRING:
        rcstring = apfl_string_move_into_new_refcounted(&constant->string);
        assert(rcstring != NULL); // TODO: This can fail!

        return (struct apfl_value) {
            .type = APFL_VALUE_STRING,
            .string = rcstring,
        };
    case APFL_EXPR_CONST_NUMBER:
        return (struct apfl_value) {
            .type = APFL_VALUE_NUMBER,
            .number = constant->number,
        };
    }

    assert(false);
}

static struct apfl_result
evaluate_list_expr_to_list(apfl_ctx ctx, struct apfl_expr *expr, struct apfl_list *out)
{
    struct apfl_result result = evaluate(ctx, expr);
    if (result.type != APFL_RESULT_OK) {
        return result;
    }

    if (result.value.type != APFL_VALUE_LIST) {
        apfl_value_deinit(&result.value);
        return (struct apfl_result) { .type = APFL_RESULT_ERR };
    }

    struct apfl_list *list = result.value.list;

    if (!apfl_resizable_ensure_cap_for_more_elements(
        sizeof(struct apfl_value),
        (void **)&out->items,
        out->len,
        &out->cap,
        list->len
    )) {
        apfl_value_deinit(&result.value);
        return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
    }

    for (size_t i = 0; i < list->len; i++) {
        if (!apfl_value_copy(&out->items[out->len], list->items[i])) {
            apfl_value_deinit(&result.value);
            return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
        }
        out->len++;
    }

    apfl_value_deinit(&result.value);
    return (struct apfl_result) { .type = APFL_RESULT_OK, .value.type = APFL_VALUE_NIL };
}

static struct apfl_result
evaluate_expr_list_into_list(apfl_ctx ctx, struct apfl_expr_list *list, struct apfl_list *out)
{
    for (size_t i = 0; i < list->len; i++) {
        struct apfl_expr_list_item *item = &list->items[i];

        if (item->expand) {
            struct apfl_result result = evaluate_list_expr_to_list(ctx, item->expr, out);
            if (result.type != APFL_RESULT_OK) {
                return result;
            }
        } else {
            struct apfl_result result = evaluate(ctx, item->expr);
            if (result.type != APFL_RESULT_OK) {
                return result;
            }

            if (!apfl_resizable_append(
                sizeof(struct apfl_value),
                (void **)&out->items,
                &out->len,
                &out->cap,
                &result.value,
                1
            )) {
                apfl_value_deinit(&result.value);
                return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
            }
        }
    }

    return (struct apfl_result) { .type = APFL_RESULT_OK, .value.type = APFL_VALUE_NIL };
}

static struct apfl_result
evaluate_list(apfl_ctx ctx, struct apfl_expr_list *list)
{
    struct apfl_list *out = apfl_list_new();
    if (out == NULL) {
        return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
    }

    struct apfl_result result = evaluate_expr_list_into_list(ctx, list, out);
    if (result.type != APFL_RESULT_OK) {
        DESTROY(out, apfl_list_deinit);
        return result;
    }

    return (struct apfl_result) {
        .type = APFL_RESULT_OK,
        .value = {
            .type = APFL_VALUE_LIST,
            .list = out,
        },
    };
}

static struct apfl_result
evaluate(apfl_ctx ctx, struct apfl_expr *expr)
{
    (void)ctx;
    switch (expr->type) {
    case APFL_EXPR_CONSTANT:
        return (struct apfl_result) {
            .type = APFL_RESULT_OK,
            .value = evaluate_constant(&expr->constant),
        };
    case APFL_EXPR_LIST:
        return evaluate_list(ctx, &expr->list);
    case APFL_EXPR_VAR:
    case APFL_EXPR_CALL:
    case APFL_EXPR_DICT:
    case APFL_EXPR_SIMPLE_FUNC:
    case APFL_EXPR_COMPLEX_FUNC:
    case APFL_EXPR_ASSIGNMENT:
    case APFL_EXPR_DOT:
    case APFL_EXPR_AT:
        break; // Not implemented yet
    }

    return (struct apfl_result) { .type = APFL_RESULT_ERR };
}

struct apfl_result
apfl_eval(apfl_ctx ctx, struct apfl_expr expr)
{
    struct apfl_result result = evaluate(ctx, &expr);
    apfl_expr_deinit(&expr);
    return result;
}