#include <assert.h>          // assert
#include <errno.h>           // errno
#include <stddef.h>          // NULL, size_t
#include <stdio.h>           // fclose
#include <stdlib.h>          // calloc, free
#include <string.h>          // memcpy

#include "gemtext-parser.h"

int lineBufferInit(lineBuffer *lb) {
    char *buf = calloc(1, LBUF_SIZE);
    if (buf == NULL) return 2;
    lb->len = 0;
    lb->capacity = LBUF_SIZE;
    lb->buf = buf;
    lb->cursor = buf;
    return 0;
}

int gemtextParserInit(gemtextParser *parser, FILE *stream) {
    int ret = 0;

    parser->stream = stream;
    parser->mode = normalMode;
    parser->state = lineStart;
    parser->linkUrl = NULL;
    ret = lineBufferInit(&parser->buffer);
    return ret;
}

gemtextParser* gemtextParserNew(FILE *stream) {
    gemtextParser *parser = calloc(1, sizeof(gemtextParser));
    if (parser == NULL)
        return NULL;
    if (gemtextParserInit(parser, stream) != 0) {
        free(parser);
        return NULL;
    }
    return parser;
}

void gemtextParserDeinit(gemtextParser *parser) {
    fclose(parser->stream);
    free(parser->buffer.buf);
    if (parser->linkUrl != NULL) {
        free(parser->linkUrl);
    }
}

void gemtextParserDestroy(gemtextParser *parser) {
    gemtextParserDeinit(parser);
    free(parser);
}

int gemtextLineQueueInit(gemtextLineQueue *queue) {
    int ret;

    queue->head = NULL;
    queue->tail = NULL;
    ret = pthread_mutex_init(&queue->mutex, NULL);
    if (ret != 0)
        return ret;
    return pthread_cond_init(&queue->cond, NULL);
}

void gemtextLineQueuePush(gemtextLineQueue *queue, gemtextLine *line) {
    pthread_mutex_lock(&queue->mutex);
    if (queue->tail == NULL) {
        queue->tail = queue->head = line;
    } else {
        line->next = queue->tail;
        queue->tail->prev = line;
        queue->tail = line;
    }
    queue->count++;
    pthread_mutex_unlock(&queue->mutex);
}

gemtextLine* gemtextLineQueuePop(gemtextLineQueue *lq) {
    gemtextLine *line;

    while (lq->count == 0)
        pthread_cond_wait(&lq->cond, &lq->mutex);
    pthread_mutex_lock(&lq->mutex);
    lq->count++;
    line = lq->head;
    if (line->lineType == endOfStream)
        return line;
    if (lq->tail == lq->head) {
        lq->tail = lq->head = NULL;
    } else {
        lq->head = lq->head->prev;
    }
    pthread_mutex_unlock(&lq->mutex);
    line->prev = line->next = NULL;
    return line;
}

gemtextLine* gemtextLineQueueTryPop(gemtextLineQueue *lq) {
    gemtextLine *line;

    if (lq->count == 0)
        return NULL;
    pthread_mutex_lock(&lq->mutex);
    lq->count++;
    line = lq->head;
    if (line->lineType == endOfStream)
        return line;
    if (lq->tail == lq->head) {
        lq->tail = lq->head = NULL;
    } else {
        lq->head = lq->head->prev;
    }
    pthread_mutex_unlock(&lq->mutex);
    line->prev = line->next = NULL;
    return line;
}

void gemtextLineDeinit(gemtextLine *line) {
    switch (line->lineType) {
    case linkLine:
        if (line->link->display != NULL) {
            free(line->link->display);
        }
        free(line->link->url);
        free(line->link);
        break;
    case preformattedLine:
        if (line->node->altText != NULL) {
            free(line->node->altText);
        }
        free(line->node->body);
        free(line->node);
        break;
    case endOfStream:
        break;
    default:
        free(line->str);
        break;
    }
    free(line);
}

int lineBufferExtend(lineBuffer *lb, size_t len) {
    char  *buf = calloc(1, lb->capacity + len);
    if (buf == NULL) return 2;
    memcpy(buf, lb->buf, lb->len);
    free(lb->buf);
    lb->buf = buf;
    lb->cursor = buf + lb->len;
    return 0;
}

int lineBufferAppendChar(lineBuffer *lb, char c) {
    int ret    = 0;

    if (lb->len >= lb->capacity - 1) {
        ret = lineBufferExtend(lb, LBUF_SIZE);
        if (ret != 0) return ret;
    }
    *lb->cursor = c;
    lb->cursor++;
    lb->len++;
    return ret;
}

void lineBufferAppendCharUnchecked(lineBuffer *lb, char c) {
    *lb->cursor = c;
    lb->cursor++;
    lb->len++;
}

int lineBufferAppendString(lineBuffer *lb, char *c, size_t len) {
    int    ret = 0, i = 0;
    size_t rem = 0;

    // Find the remaining length
    rem = lb->capacity - lb->len;
    // if the length won't fit our string, extend the buffer.
    // We do len - rem + LBUF_SIZE for a safety margin
    if (rem < len) {
        ret = lineBufferExtend(lb, len - rem + LBUF_SIZE);
        if (ret != 0) return ret;
    }

    for (i = 0; i < len; i++) {
        // We use 'unchecked' because we did our checks above
        lineBufferAppendCharUnchecked(lb, *c);
        c++;
    }
    return ret;
}

void lineBufferRewind(lineBuffer *lb) {
    lb->len--;
    lb->cursor--;
}

void lineBufferReset(lineBuffer *lb) {
    lb->len = 0;
    lb->cursor = lb->buf;
}

int gemtextParserSendPreformatted(gemtextParser *parser, gemtextLineQueue *lq) {
    preformattedNode *node;
    gemtextLine      *line;
    char             *buf;

    line = calloc(1, sizeof(gemtextLine));
    if (line == NULL) return errno;
    line->lineType = preformattedLine;
    node = calloc(1, sizeof(preformattedNode));
    if (node == NULL) return errno;
    // back up our cursor four spaces and insert a lf char
    parser->buffer.cursor -= 4;
    parser->buffer.len -= 4;
    lineBufferAppendCharUnchecked(&parser->buffer, '\n');
    buf = strndup(parser->buffer.buf, parser->buffer.len);
    if (buf == NULL) return errno;
    node->altText = parser->altText;
    parser->altText = NULL;
    node->body = buf;
    line->node = node;
    gemtextLineQueuePush(lq, line);
    lineBufferReset(&parser->buffer);
    parser->state = lineStart;
    parser->mode = normalMode;
    return 0;
}

int gemtextParserSendLink(gemtextParser *parser, gemtextLineQueue *lq) {
    gemtextLink *link;
    gemtextLine *line;
    char        *url = NULL, *display = NULL;

    link = calloc(1, sizeof(gemtextLink));
    if (link == NULL) return errno;
    link->display = link->url = NULL;
    line = calloc(1, sizeof(gemtextLine));
    if (line == NULL) {
        free(link);
        return errno;
    }
    if (parser->linkUrl == NULL) {
        url = strndup(parser->buffer.buf, parser->buffer.len - 1);
    } else {
        url = parser->linkUrl;
        display = strndup(parser->buffer.buf, parser->buffer.len);
        if (display == NULL) {
            free(link);
            free(line);
            return errno;
        }
    }
    link->url = url;
    link->display = display;
    line->lineType = linkLine;
    line->link = link;
    gemtextLineQueuePush(lq, line);
    lineBufferReset(&parser->buffer);
    parser->state = lineStart;
    parser->mode = normalMode;
    parser->linkUrl = NULL;
    return 0;
}

int gemtextParserSend(gemtextParser *parser, gemtextLineType lt, gemtextLineQueue *lq) {
    gemtextLine *line;
    char        *buf;

    line = calloc(1, sizeof(gemtextLine));
    if (line == NULL) return errno;
    line->lineType = lt;
    buf = strndup(parser->buffer.buf, parser->buffer.len);
    if (buf == NULL) return errno;
    line->str = buf;
    gemtextLineQueuePush(lq, line);
    lineBufferReset(&parser->buffer);
    parser->state = lineStart;
    parser->mode = normalMode;
    return 0;
}

void logParseError(int err) {
    //todo
}

void switchMode(gemtextParser *parser, gemtextParserMode mode, char c) {
    lineBufferReset(&parser->buffer);
    switch (c) {
    case ' ':
    case '\t':
        parser->state = trimStart;
        break;
    default:
        lineBufferReset(&parser->buffer);
        lineBufferAppendCharUnchecked(&parser->buffer, c);
        parser->state = normalState;
    }
    parser->mode = mode;
}

void enterPreformattedMode(gemtextParser *parser) {
    parser->mode = preformattedMode;
    parser->state = preformattedAlt;
    lineBufferReset(&parser->buffer);
}

int parseLink(gemtextParser *parser, gemtextLineQueue *lq, char c) {
    int   ret = 0;
    char *buf = NULL;

    assert(parser->mode == linkMode);
    switch (parser->state) {
    case lineStart:
        if (c != ' ' && c != '\t') {
            lineBufferReset(&parser->buffer);
            lineBufferAppendCharUnchecked(&parser->buffer, c);
            parser->state = normalState;
        } else if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
        }
        break;
    case normalState:
        if (c == ' ' || c == '\t') {
            buf = strndup(parser->buffer.buf, parser->buffer.len - 1);
            if (buf == NULL) return errno;
            parser->linkUrl = buf;
            parser->state = linkDisplayStart;
            lineBufferReset(&parser->buffer);
        } else if (c == '\n') {
            buf = strndup(parser->buffer.buf, parser->buffer.len);
            if (buf == NULL) return errno;
            ret = gemtextParserSendLink(parser, lq);
        }
        break;
    case linkDisplayStart:
        if (c == ' ' || c == '\t') {
            lineBufferRewind(&parser->buffer);
        } else if (c == '\n') {
            ret = gemtextParserSendLink(parser, lq);
        } else {
            parser->state = linkDisplay;
        }
        break;
    case linkDisplay:
        if (c == '\n') {
            ret = gemtextParserSendLink(parser, lq);
        }
        break;
    default:
        ret = 1;
        break;
    }
    return ret;
}

int parsePreformatted(gemtextParser *parser, gemtextLineQueue *lq, char c) {
    char *buf = NULL;

    assert(parser->mode == preformattedMode);
    switch (parser->state) {
    case preformattedAlt:
        if (c == '\n') {
            parser->state = normalState;
            if (parser->buffer.len > 0) {
                buf = strncpy(buf, parser->buffer.buf, parser->buffer.len);
                if (buf == NULL) return errno;
                parser->altText = buf;
            }
        }
        break;
    case normalState:
        if (c == '\n') {
            parser->state = lineStart;
        }
        break;
    case lineStart:
        if (c == '\n') {
            parser->state = firstBacktickChar;
        }
        break;
    case firstBacktickChar:
        if (c == '`') {
            parser->state = secondBacktickChar;
        } else {
            parser->state = normalState;
        }
        break;
    case secondBacktickChar:
        if (c == '`') {
            parser->state = thirdBacktickChar;
        } else {
            parser->state = normalState;
        }
        break;
    case thirdBacktickChar:
        if (c == '\n') {
            gemtextParserSendPreformatted(parser, lq);
        } else {
            // We discard anything past the third backtick
            parser->buffer.cursor--;
            parser->buffer.len--;
        }
        break;
    default:
        return 1;
    }
    return 0;
}

int parseQuote(gemtextParser *parser, gemtextLineQueue *lq, char c) {
    int ret = 0;

    switch (parser->state) {
    case lineStart:
        if (c == '>') {
            parser->state = trimStart;
            lineBufferRewind(&parser->buffer);
        } else {
            lineBufferRewind(&parser->buffer);
            ret = gemtextParserSend(parser, quoteLine, lq);
            if (ret) return ret;
            ret = fseek(parser->stream, -1, SEEK_CUR);
            if (ret) return ret;
            parser->state = lineStart;
            parser->mode = normalMode;
        }
        break;
    case normalState:
        if (c == '\n') {
            parser->state = lineStart;
        }
        break;
    case trimStart:
        if (c == ' ' || c == '\t') {
            // rewind and trim the whitespace
            parser->buffer.len--;
            parser->buffer.cursor--;
        } else if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
        } else {
            parser->state = normalState;
        }
        break;
    default:
        // Should be unreachable
        ret = 1;
        break;
    }
    return ret;
}

int parseGeneric(gemtextParser *parser, gemtextLineQueue *lq, gemtextLineType lt, char c) {
    int ret = 0;

    switch (parser->state) {
    case lineStart:
    case trimStart:
        if (c == ' ' || c == '\t') {
            // rewind the cursor to trim the line start
            parser->buffer.len--;
            parser->buffer.cursor--;
        } else if (c == '\n') {
            ret = gemtextParserSend(parser, lt, lq);
        } else {
            parser->state = normalState;
        }
        break;
    case normalState:
        if (c == '\n') {
            ret = gemtextParserSend(parser, lt, lq);
        }
        break;
    default:
        // Should be unreachable
        ret = 1;
        break;
    }
    return ret;
}

int parseNormal(gemtextParser *parser, gemtextLineQueue *lq, char c) {
    int ret;

    switch (parser->state) {
    case lineStart:
        switch (c) {
        case '=':
            parser->state = firstLinkChar;
            break;
        case '>':
            parser->mode = quoteMode;
            parser->state = trimStart;
            lineBufferRewind(&parser->buffer);
            break;
        case '*':
            parser->mode = listMode;
            parser->state = trimStart;
            lineBufferRewind(&parser->buffer);
            break;
        case '#':
            parser->state = firstHashChar;
            break;
        case '`':
            parser->state = firstBacktickChar;
            break;
        case '\n':
            ret = gemtextParserSend(parser, normalLine, lq);
            if (ret) return ret;
            break;
        default:
            break;
        }
        break;
    case firstLinkChar:
        if (c == '>') {
            parser->mode = linkMode;
            parser->state = lineStart;
        } else if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
            if (ret) return ret;
        } else {
            parser->state = normalState;
        }
        break;
    case firstHashChar:
        if (c == '#') {
            parser->state = secondHashChar;
        } else if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
            if (ret) return ret;
        } else {
            switchMode(parser, h1Mode, c);
        }
        break;
    case secondHashChar:
        if (c == '#') {
            parser->mode = h3Mode;
            parser->state = trimStart;
            lineBufferReset(&parser->buffer);
        } else if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
            if (ret) return ret;
        } else {
            switchMode(parser, h2Mode, c);
        }
        break;
    case thirdHashChar:
        if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
            if (ret) return ret;
        } else {
            switchMode(parser, h3Mode, c);
        }
        break;
    case firstBacktickChar:
        if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
            if (ret) return ret;
        } else if (c == '`') {
            parser->state = secondBacktickChar;
        } else {
            parser->state = normalState;
            parser->mode = normalMode;
        }
    case secondBacktickChar:
        if (c == '`') {
            enterPreformattedMode(parser);
        } else if (c == '\n') {
            ret = gemtextParserSend(parser, normalLine, lq);
            if (ret) return ret;
        } else {
            parser->state = normalState;
            parser->mode = normalMode;
        }
    default:
        break;
    }
    return 0;
}

int parseGemtext(gemtextParser *parser, gemtextLineQueue *lq) {
    char         c;
    int          ret;
    gemtextLine *line;

    for (;;) {
        ret = fread(&c, 1, 1, parser->stream);
        if (ret == 1) {
            ret = lineBufferAppendChar(&parser->buffer, c);
            if (ret) {
                logParseError(ret);
                return ret;
            }
        } else {
            switch (parser->mode) {
            case normalMode:
                ret = gemtextParserSend(parser, normalLine, lq);
                break;
            case preformattedMode:
                ret = gemtextParserSendPreformatted(parser, lq);
                break;
            case quoteMode:
                ret = gemtextParserSend(parser, quoteLine, lq);
                break;
            case linkMode:
                ret = gemtextParserSendLink(parser, lq);
                break;
            case h1Mode:
                ret = gemtextParserSend(parser, h1Line, lq);
                break;
            case h2Mode:
                ret = gemtextParserSend(parser, h2Line, lq);
                break;
            case h3Mode:
                ret = gemtextParserSend(parser, h3Line, lq);
                break;
            case listMode:
                ret = gemtextParserSend(parser, listLine, lq);
                break;
            }
            if (ret) return ret;
            line = calloc(1, sizeof(gemtextLine));
            if (line == NULL) return errno;
            line->lineType = endOfStream;
            line->prev = line->next = NULL;
            line->str = NULL;
            gemtextLineQueuePush(lq, line);
            break;
        }
        switch (parser->mode) {
        case normalMode:
            ret = parseNormal(parser, lq, c);
            break;
        case preformattedMode:
            ret = parsePreformatted(parser, lq, c);
            break;
        case quoteMode:
            ret = parseQuote(parser, lq, c);
            break;
        case linkMode:
            ret = parseLink(parser, lq, c);
            break;
        case h1Mode:
            ret = parseGeneric(parser, lq, h1Line, c);
            break;
        case h2Mode:
            ret = parseGeneric(parser, lq, h2Line, c);
            break;
        case h3Mode:
            ret = parseGeneric(parser, lq, h3Line, c);
            break;
        case listMode:
            ret = parseGeneric(parser, lq, listLine, c);
            break;
        }
        if (ret) {
            logParseError(ret);
            return ret;
        }
    }
    return 0;
}