#include <emscripten.h>

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

#include "../../src/apfl.h"
#include "../../src/format.h"

struct playground_source_reader_data {
    char *str;
    size_t len;
    size_t off;
    bool eof;
};

EM_ASYNC_JS(char *, get_input, (int need), {
    var s = await window.playground_get_input(!!need);
    var lengthBytes = lengthBytesUTF8(s)+1;
    var stringOnWasmHeap = _malloc(lengthBytes);
    stringToUTF8(s, stringOnWasmHeap, lengthBytes);
    return stringOnWasmHeap;
});

EM_JS(void, web_writer, (int error, const char* str, int size), {
    window.playground_write(!!error, UTF8ToString(str, size));
});

static bool
web_fmt_write(void *opaque, const char *buf, size_t len)
{
    int error = (int)opaque;
    web_writer(error, buf, (int)len);
    return true;
}

static bool
playground_source_reader_cb(void *context, char *buf, size_t *len, bool need)
{
    struct playground_source_reader_data *r = context;

    size_t remain = r->len - r->off;
    if (remain == 0) {
        free(r->str);
        r->str = get_input(need ? 1 : 0);
        assert(r->str != NULL);

        r->len = strlen(r->str);
        r->off = 0;
    }

    remain = r->len - r->off;
    assert(remain > 0);

    if (remain < *len) {
        *len = remain;
    }
    memcpy(buf, r->str+r->off, *len);
    r->off += *len;

    return true;
}

static void
dump_stack_error(apfl_ctx ctx, apfl_iterative_runner runner, struct apfl_format_writer w_err)
{
    if (apfl_iterative_runner_has_error_on_stack(runner)) {
        assert(apfl_debug_print_val(ctx, -1, w_err));
    }
}

int
main(void)
{
    int rv = 0;

    struct apfl_format_writer w_ok = {.write = web_fmt_write, .opaque = (void *)0};
    struct apfl_format_writer w_err = {.write = web_fmt_write, .opaque = (void *)1};

    apfl_ctx ctx = apfl_ctx_new((struct apfl_config) {
        .allocator = apfl_allocator_default(),
        .output_writer = w_ok,
    });
    if (ctx == NULL) {
        assert(apfl_format_put_string(w_err, "Failed to init the context\n"));
        return 1;
    }

    struct playground_source_reader_data source_reader_data = {
        .str = NULL,
        .len = 0,
        .off = 0,
        .eof = false,
    };

    apfl_iterative_runner runner = apfl_iterative_runner_new(ctx, (struct apfl_source_reader) {
        .callback = playground_source_reader_cb,
        .opaque = &source_reader_data,
    });
    if (runner == NULL) {
        apfl_ctx_destroy(ctx);
        assert(apfl_format_put_string(w_err, "Failed to init runner\n"));
        return 1;
    }

    while (apfl_iterative_runner_next(runner)) {
        switch (apfl_iterative_runner_get_result(runner)) {
        case APFL_RESULT_OK :
            if (apfl_get_type(ctx, -1) == APFL_VALUE_NIL) {
                apfl_drop(ctx, -1);
            } else {
                assert(apfl_debug_print_val(ctx, -1, w_ok));
            }
            break;
        case APFL_RESULT_ERR:
            dump_stack_error(ctx, runner, w_err);
            assert(apfl_format_put_string(w_err, "Error occurred during evaluation.\n"));
            break;
        case APFL_RESULT_ERR_FATAL:
            dump_stack_error(ctx, runner, w_err);
            assert(apfl_format_put_string(w_err, "Fatal error occurred during evaluation.\n"));
            rv = 1;
            goto exit;
        }
    }

exit:
    free(source_reader_data.str);
    apfl_iterative_runner_destroy(runner);
    apfl_ctx_destroy(ctx);
    return rv;
}