#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "parser.h"

int ConsumeWhitespace(char* s) {
    int i = 0;
    while (s[i])
    {
        switch (s[i])
        {
            case ' ':
            case '\t':
            case '\r':
                break;
            default:
                goto end;
        }
        i++;
    }
end:
    return i;
}

/* Return a pointer to the first line-ending character
 * in this line (i.e. CR in case of CRLF, LF in case of just LF,
 * or NUL if this line does not end with CR or LF). */
char* LineEnd(char* line)
{
    while (*line)
    {
        switch (*line)
        {
            case '\r':
                if (line[1] == '\n')
                    return line;
                break;
            case '\n':
                return line;
                break;
            default:
                break;
        }
        line++;
    }
    return line;
}

/* A la glibc 2.11 strchrnul */
char* strchrnul(const char* s, int c) {
    while (*s && (*s != c))
        s++;
    return (char*)s;
}

/* Parse a line in-place, without allocating any new memory */
enum parse_result
ParseLine(struct parse_state* s, struct line* l)
{
    int i = 0, link_end;
    char* line;
    char* line_end;
    char* line_next;
    enum parse_result res = PARSE_LINE;

    line = s->buf;
    line_end = LineEnd(s->buf);
    if (*line_end == 0)
        line_next = line_end;
    else if (*line_end == '\n')
        line_next = line_end + 1;
    else if (*line_end == '\r')
        line_next = line_end + 2;

    *line_end = 0;

    if (strncmp(line, "```", 3) == 0) {
        s->preformatted = !s->preformatted;
        res = PARSE_NOLINE;
    } else if (s->preformatted) {
        l->type = LT_PRETEXT;
        l->text = line;
    } else if (*line == '>') {
        i++;
        i += ConsumeWhitespace(&line[i]);
        l->type = LT_QUOTE;
        l->text = &line[i];
    } else if (*line == '#') {
        i = strchrnul(line, ' ') - line;
        if (i > 3) i = 3;
        l->level = i;
        i += ConsumeWhitespace(&line[i]);
        l->text = &line[i];
        l->type = LT_HEADING;
    } else if (*line == '*') {
        i++;
        i += ConsumeWhitespace(&line[i]);
        l->type = LT_LISTITEM;
        l->text = &line[i];
    } else if (strncmp(line, "=>", 2) == 0) {
        l->type = LT_LINK;
        i = 2;
        i += ConsumeWhitespace(&line[i]);
        l->url = &line[i];
        for (; line[i] && !isspace(line[i]); i++);
        if (line[i] == 0) {
            /* no title */
            l->text = l->url;
        } else {
            line[i++] = 0;
            l->text = &line[i];
        }
    } else {
        /* just text */
        l->type = LT_TEXT;
        l->text = line;
    }

    s->buf = line_next;
    return res;
}