/*
 * blogc: A blog compiler.
 * Copyright (C) 2015 Rafael G. Martins <rafael@rafaelmartins.eng.br>
 *
 * This program can be distributed under the terms of the BSD License.
 * See the file COPYING.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /* HAVE_CONFIG_H */

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

#include "utils/utils.h"
#include "content-parser.h"
#include "error.h"


// this is a half ass implementation of a markdown-like syntax. bugs are
// expected. feel free to improve the parser and and new features.


// TODO: inline elements: links, emphasis, code, images, line breaks
// TODO: automatic scaping of html entities
// TODO: automatic links
// TODO: error handling


typedef enum {
    CONTENT_START_LINE = 1,
    CONTENT_HEADER,
    CONTENT_HEADER_TITLE_START,
    CONTENT_HEADER_TITLE,
    CONTENT_HTML,
    CONTENT_HTML_END,
    CONTENT_BLOCKQUOTE,
    CONTENT_BLOCKQUOTE_START,
    CONTENT_BLOCKQUOTE_END,
    CONTENT_CODE,
    CONTENT_CODE_START,
    CONTENT_CODE_END,
    CONTENT_UNORDERED_LIST_OR_HORIZONTAL_RULE,
    CONTENT_HORIZONTAL_RULE,
    CONTENT_UNORDERED_LIST_START,
    CONTENT_UNORDERED_LIST_END,
    CONTENT_ORDERED_LIST,
    CONTENT_ORDERED_LIST_SPACE,
    CONTENT_ORDERED_LIST_START,
    CONTENT_ORDERED_LIST_END,
    CONTENT_PARAGRAPH,
    CONTENT_PARAGRAPH_END,
} blogc_content_parser_state_t;


char*
blogc_content_parse(const char *src, size_t src_len, blogc_error_t **err)
{
    if (err == NULL || *err != NULL)
        return NULL;

    size_t current = 0;
    size_t start = 0;
    size_t end = 0;

    unsigned int header_level = 0;
    char *prefix = NULL;
    size_t prefix_len = 0;
    char *tmp = NULL;
    char *tmp2 = NULL;
    char **tmpv = NULL;

    char d;

    b_slist_t *lines = NULL;

    b_string_t *rv = b_string_new();
    b_string_t *tmp_str = NULL;

    blogc_content_parser_state_t state = CONTENT_START_LINE;

    while (current < src_len) {
        char c = src[current];
        bool is_last = current == src_len - 1;

        switch (state) {

            case CONTENT_START_LINE:
                if (c == '\n' || c == '\r')
                    break;
                if (c == '#') {
                    header_level = 1;
                    state = CONTENT_HEADER;
                    break;
                }
                if (c == '*' || c == '+' || c == '-') {
                    state = CONTENT_UNORDERED_LIST_OR_HORIZONTAL_RULE;
                    start = current;
                    d = c;
                    break;
                }
                if (c >= '0' && c <= '9') {
                    state = CONTENT_ORDERED_LIST;
                    start = current;
                    break;
                }
                if (c == ' ' || c == '\t') {
                    state = CONTENT_CODE;
                    start = current;
                    break;
                }
                if (c == '<') {
                    state = CONTENT_HTML;
                    start = current;
                    break;
                }
                if (c == '>') {
                    state = CONTENT_BLOCKQUOTE;
                    start = current;
                    break;
                }
                start = current;
                state = CONTENT_PARAGRAPH;
                break;

            case CONTENT_HEADER:
                if (c == '#') {
                    header_level += 1;
                    break;
                }
                if (c == ' ' || c == '\t') {
                    state = CONTENT_HEADER_TITLE_START;
                    break;
                }
                *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                    current, "Malformed header, no space or tab after '#'");
                break;

            case CONTENT_HEADER_TITLE_START:
                if (c == ' ' || c == '\t')
                    break;
                if (c != '\n' || c != '\r') {
                    start = current;
                    state = CONTENT_HEADER_TITLE;
                    break;
                }
                *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                    current, "Empty header");
                break;

            case CONTENT_HEADER_TITLE:
                if (c == '\n' || c == '\r' || is_last) {
                    end = is_last ? src_len : current;
                    tmp = b_strndup(src + start, end - start);
                    b_string_append_printf(rv, "<h%d>%s</h%d>\n", header_level,
                        tmp, header_level);
                    free(tmp);
                    tmp = NULL;
                    state = CONTENT_START_LINE;
                    start = current;
                    break;
                }
                break;

            case CONTENT_HTML:
                if (c == '\n' || c == '\r' || is_last) {
                    state = CONTENT_HTML_END;
                    end = is_last ? src_len : current;
                }
                if (!is_last)
                    break;

            case CONTENT_HTML_END:
                if (c == '\n' || c == '\r' || is_last) {
                    tmp = b_strndup(src + start, end - start);
                    b_string_append_printf(rv, "%s\n", tmp);
                    free(tmp);
                    tmp = NULL;
                    state = CONTENT_START_LINE;
                    start = current;
                }
                else
                    state = CONTENT_HTML;
                break;

            case CONTENT_BLOCKQUOTE:
                if (c == ' ' || c == '\t')
                    break;
                prefix = b_strndup(src + start, current - start);
                state = CONTENT_BLOCKQUOTE_START;

            case CONTENT_BLOCKQUOTE_START:
                if (c == '\n' || c == '\r' || is_last) {
                    end = is_last ? src_len : current;
                    tmp = b_strndup(src + start, end - start);
                    if (b_str_starts_with(tmp, prefix)) {
                        lines = b_slist_append(lines, b_strdup(tmp + strlen(prefix)));
                        state = CONTENT_BLOCKQUOTE_END;
                    }
                    else {
                        *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                            current, "Malformed blockquote, must use same prefix "
                            "as previous line(s): %s", prefix);
                    }
                    free(tmp);
                    tmp = NULL;
                }
                if (!is_last)
                    break;

            case CONTENT_BLOCKQUOTE_END:
                if (c == '\n' || c == '\r' || is_last) {
                    tmp_str = b_string_new();
                    for (b_slist_t *l = lines; l != NULL; l = l->next) {
                        if (l->next == NULL)
                            b_string_append_printf(tmp_str, "%s", l->data);
                        else
                            b_string_append_printf(tmp_str, "%s\n", l->data);
                    }
                    tmp = blogc_content_parse(tmp_str->str, tmp_str->len, err);
                    if (*err == NULL) {
                        b_string_append_printf(rv, "<blockquote>%s</blockquote>\n",
                            tmp);
                    }
                    free(tmp);
                    tmp = NULL;
                    b_string_free(tmp_str, true);
                    tmp_str = NULL;
                    b_slist_free_full(lines, free);
                    lines = NULL;
                    free(prefix);
                    prefix = NULL;
                    state = CONTENT_START_LINE;
                    start = current;
                }
                else {
                    start = current;
                    state = CONTENT_BLOCKQUOTE_START;
                }
                break;

            case CONTENT_CODE:
                if (c == ' ' || c == '\t')
                    break;
                prefix = b_strndup(src + start, current - start);
                state = CONTENT_CODE_START;

            case CONTENT_CODE_START:
                if (c == '\n' || c == '\r' || is_last) {
                    end = is_last ? src_len : current;
                    tmp = b_strndup(src + start, end - start);
                    if (b_str_starts_with(tmp, prefix)) {
                        lines = b_slist_append(lines, b_strdup(tmp + strlen(prefix)));
                        state = CONTENT_CODE_END;
                    }
                    else {
                        *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                            current, "Malformed code block, must use same prefix "
                            "as previous line(s): '%s'", prefix);
                    }
                    free(tmp);
                    tmp = NULL;
                }
                if (!is_last)
                    break;

            case CONTENT_CODE_END:
                if (c == '\n' || c == '\r' || is_last) {
                    b_string_append(rv, "<pre><code>");
                    for (b_slist_t *l = lines; l != NULL; l = l->next) {
                        if (l->next == NULL)
                            b_string_append_printf(rv, "%s", l->data);
                        else
                            b_string_append_printf(rv, "%s\n", l->data);
                    }
                    b_string_append(rv, "</code></pre>\n");
                    b_slist_free_full(lines, free);
                    lines = NULL;
                    free(prefix);
                    prefix = NULL;
                    state = CONTENT_START_LINE;
                    start = current;
                }
                else {
                    start = current;
                    state = CONTENT_CODE_START;
                }
                break;

            case CONTENT_UNORDERED_LIST_OR_HORIZONTAL_RULE:
                if (c == d) {
                    state = CONTENT_HORIZONTAL_RULE;
                    break;
                }
                if (c == ' ' || c == '\t')
                    break;
                prefix = b_strndup(src + start, current - start);
                state = CONTENT_UNORDERED_LIST_START;
                break;

            case CONTENT_HORIZONTAL_RULE:
                if (c == d) {
                    break;
                }
                if (c == '\n' || c == '\r' || is_last) {
                    b_string_append(rv, "<hr />\n");
                    state = CONTENT_START_LINE;
                    start = current;
                    d = '\0';
                    break;
                }
                *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                    current, "Malformed horizontal rule, must use only '%c'", d);
                break;

            case CONTENT_UNORDERED_LIST_START:
                if (c == '\n' || c == '\r' || is_last) {
                    end = is_last ? src_len : current;
                    tmp = b_strndup(src + start, end - start);
                    if (b_str_starts_with(tmp, prefix)) {
                        lines = b_slist_append(lines, b_strdup(tmp + strlen(prefix)));
                    }
                    else {
                        *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                            current, "Malformed unordered list, must use same prefix "
                            "as previous line(s): %s", prefix);
                    }
                    free(tmp);
                    tmp = NULL;
                    state = CONTENT_UNORDERED_LIST_END;
                }
                if (!is_last)
                    break;

            case CONTENT_UNORDERED_LIST_END:
                if (c == '\n' || c == '\r' || is_last) {
                    b_string_append(rv, "<ul>\n");
                    for (b_slist_t *l = lines; l != NULL; l = l->next)
                        b_string_append_printf(rv, "<li>%s</li>\n", l->data);
                    b_string_append(rv, "</ul>\n");
                    b_slist_free_full(lines, free);
                    lines = NULL;
                    free(prefix);
                    prefix = NULL;
                    state = CONTENT_START_LINE;
                    start = current;
                }
                else {
                    start = current;
                    state = CONTENT_UNORDERED_LIST_START;
                }
                break;

            case CONTENT_ORDERED_LIST:
                if (c >= '0' && c <= '9')
                    break;
                if (c == '.') {
                    state = CONTENT_ORDERED_LIST_SPACE;
                    break;
                }
                state = CONTENT_PARAGRAPH;
                break;

            case CONTENT_ORDERED_LIST_SPACE:
                if (c == ' ' || c == '\t')
                    break;
                prefix_len = current - start;
                state = CONTENT_ORDERED_LIST_START;

            case CONTENT_ORDERED_LIST_START:
                if (c == '\n' || c == '\r' || is_last) {
                    end = is_last ? src_len : current;
                    tmp = b_strndup(src + start, end - start);
                    if (strlen(tmp) >= prefix_len) {
                        tmp2 = b_strndup(tmp, prefix_len);
                        tmpv = b_str_split(tmp2, '.', 2);
                        free(tmp2);
                        tmp2 = NULL;
                        if (b_strv_length(tmpv) != 2) {
                            *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                                current, "Malformed ordered list, prefix must be a "
                                "number, followed by a '.', followed by the content. "
                                "Content must be aligned with content from previous line(s)");
                            goto err_li;
                        }
                        for (unsigned int i = 0; tmpv[0][i] != '\0'; i++) {
                            if (!(tmpv[0][i] >= '0' && tmpv[0][i] <= '9')) {
                                *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                                    current, "Malformed ordered list, prefix must be a "
                                    "number, followed by a '.', followed by the content. "
                                    "Content must be aligned with content from previous line(s)");
                                goto err_li;
                            }
                        }
                        for (unsigned int i = 0; tmpv[1][i] != '\0'; i++) {
                            if (!(tmpv[1][i] == ' ' || tmpv[1][i] == '\t')) {
                                *err = blogc_error_parser(BLOGC_ERROR_CONTENT_PARSER, src, src_len,
                                    current, "Malformed ordered list, prefix must be a "
                                    "number, followed by a '.', followed by the content. "
                                    "Content must be aligned with content from previous line(s)");
                                goto err_li;
                            }
                        }
                        lines = b_slist_append(lines, b_strdup(tmp + prefix_len));
                        state = CONTENT_ORDERED_LIST_END;
err_li:
                        b_strv_free(tmpv);
                        tmpv = NULL;
                    }
                    free(tmp);
                    tmp = NULL;
                }
                if (!is_last)
                    break;

            case CONTENT_ORDERED_LIST_END:
                if (c == '\n' || c == '\r' || is_last) {
                    b_string_append(rv, "<ol>\n");
                    for (b_slist_t *l = lines; l != NULL; l = l->next)
                        b_string_append_printf(rv, "<li>%s</li>\n", l->data);
                    b_string_append(rv, "</ol>\n");
                    b_slist_free_full(lines, free);
                    lines = NULL;
                    free(prefix);
                    prefix = NULL;
                    state = CONTENT_START_LINE;
                    start = current;
                }
                else {
                    start = current;
                    state = CONTENT_ORDERED_LIST_START;
                }
                break;

            case CONTENT_PARAGRAPH:
                if (c == '\n' || c == '\r' || is_last) {
                    state = CONTENT_PARAGRAPH_END;
                    end = is_last ? src_len : current;
                }
                if (!is_last)
                    break;

            case CONTENT_PARAGRAPH_END:
                if (c == '\n' || c == '\r' || is_last) {
                    tmp = b_strndup(src + start, end - start);
                    b_string_append_printf(rv, "<p>%s</p>\n", tmp);
                    free(tmp);
                    tmp = NULL;
                    state = CONTENT_START_LINE;
                    start = current;
                }
                else
                    state = CONTENT_PARAGRAPH;
                break;

        }

        if (*err != NULL)
            break;

        current++;
    }

    if (*err != NULL) {
        b_string_free(rv, true);
        return NULL;
    }

    return b_string_free(rv, false);
}