#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

#include "apfl.h"

enum repl_mode {
    REPL_TOKENIZER,
    REPL_PARSER,
    REPL_EVAL,
};

static bool
repl_source_reader(void *context, char *buf, size_t *len, bool need)
{
    (void)context;

    printf(need ? "... " : "> ");
    fflush(stdout);

    size_t maxlen = *len;

    if (fgets(buf, maxlen, stdin) == NULL) {
        if (feof(stdin)) {
            *len = 0;
            return true;
        } else {
            return false;
        }
    }

    *len = strlen(buf);
    return true;
}

static int
repl_tokenizer(apfl_tokenizer_ptr tokenizer)
{
    while (true) {
        struct apfl_error err;
        struct apfl_token token;

        switch (apfl_tokenizer_next(tokenizer, false)) {
        case APFL_PARSE_OK:
            token = apfl_tokenizer_get_token(tokenizer);
            apfl_token_print(token, stdout);
            apfl_token_deinit(&token);

            break;
        case APFL_PARSE_EOF:
            return 0;
        case APFL_PARSE_ERROR:
            err = apfl_tokenizer_get_error(tokenizer);
            apfl_error_print(err, stderr);

            if (APFL_ERROR_IS_FATAL(err)) {
                return 1;
            }
            break;
        }
    }
}

static bool
repl_parser_generic(apfl_parser_ptr parser, struct apfl_expr *expr, int *rv)
{
    while (true) {
        struct apfl_error err;

        switch (apfl_parser_next(parser)) {
        case APFL_PARSE_OK:
            *expr = apfl_parser_get_expr(parser);
            return true;
        case APFL_PARSE_EOF:
            *rv = 0;
            return false;
        case APFL_PARSE_ERROR:
            err = apfl_parser_get_error(parser);
            apfl_error_print(err, stderr);

            if (APFL_ERROR_IS_FATAL(err)) {
                *rv = 1;
                return false;
            }
            break;
        }
    }
}

static int
repl_parser(apfl_parser_ptr parser)
{
    struct apfl_expr expr;
    int rv;
    while (repl_parser_generic(parser, &expr, &rv)) {
        apfl_expr_print(expr, stdout);
        apfl_expr_deinit(&expr);
    }
    return rv;
}

static int
repl_eval(apfl_parser_ptr parser, apfl_ctx ctx)
{
    struct apfl_expr expr;
    int rv;
    while (repl_parser_generic(parser, &expr, &rv)) {
        struct apfl_result result = apfl_eval(ctx, expr);
        switch (result.type) {
        case APFL_RESULT_OK:
            apfl_value_print(result.value, stdout);
            apfl_value_deinit(&result.value);
            break;
        case APFL_RESULT_ERR:
            fprintf(stderr, "Error occurred during evaluation.\n");
            break;
        case APFL_RESULT_ERR_FATAL:
            fprintf(stderr, "Fatal error occurred during evaluation.\n");
            return 1;
        }
    }
    return rv;
}

int
main(int argc, const char **argv)
{
    int rv = 0;

    enum repl_mode mode = REPL_PARSER;

    if (argc > 1) {
        if (apfl_string_eq(argv[1], "tokenizer")) {
            mode = REPL_TOKENIZER;
        } else if (apfl_string_eq(argv[1], "parser")) {
            mode = REPL_PARSER;
        } else if (apfl_string_eq(argv[1], "eval")) {
            mode = REPL_EVAL;
        } else {
            fprintf(stderr, "Unknown mode: %s\n", argv[1]);
            return 1;
        }
    }

    apfl_tokenizer_ptr tokenizer = NULL;
    apfl_parser_ptr parser = NULL;
    apfl_ctx ctx = NULL;

    if ((tokenizer = apfl_tokenizer_new(repl_source_reader, NULL)) == NULL) {
        fprintf(stderr, "Failed initializing tokenizer\n");
        rv = 1;
        goto exit;
    }

    if (mode >= REPL_PARSER) {
        if ((parser = apfl_parser_new(apfl_tokenizer_as_token_source(tokenizer))) == NULL) {
            fprintf(stderr, "Failed initializing parser\n");
            rv = 1;
            goto exit;
        }
    }

    if (mode >= REPL_EVAL) {
        if ((ctx = apfl_ctx_new()) == NULL) {
            fprintf(stderr, "Failed initializing context\n");
            rv = 1;
            goto exit;
        }
    }

    switch (mode) {
    case REPL_TOKENIZER:
        rv = repl_tokenizer(tokenizer);
        break;
    case REPL_PARSER:
        rv = repl_parser(parser);
        break;
    case REPL_EVAL:
        rv = repl_eval(parser, ctx);
        break;
    }

exit:
    apfl_tokenizer_destroy(tokenizer);
    apfl_parser_destroy(parser);
    apfl_ctx_destroy(ctx);

    return rv;
}