//
//  damus.c
//  damus
//
//  Created by William Casarin on 2022-10-17.
//

#include "damus.h"
#include "cursor.h"
#include "bolt11.h"
#include "bech32.h"
#include <stdlib.h>
#include <string.h>

static int parse_digit(struct cursor *cur, int *digit) {
    int c;
    if ((c = peek_char(cur, 0)) == -1)
        return 0;
    
    c -= '0';
    
    if (c >= 0 && c <= 9) {
        *digit = c;
        cur->p++;
        return 1;
    }
    return 0;
}


static int parse_mention_index(struct cursor *cur, struct note_block *block) {
    int d1, d2, d3, ind;
    u8 *start = cur->p;
    
    if (!parse_str(cur, "#["))
        return 0;
    
    if (!parse_digit(cur, &d1)) {
        cur->p = start;
        return 0;
    }
    
    ind = d1;
    
    if (parse_digit(cur, &d2))
        ind = (d1 * 10) + d2;
    
    if (parse_digit(cur, &d3))
        ind = (d1 * 100) + (d2 * 10) + d3;
    
    if (!parse_char(cur, ']')) {
        cur->p = start;
        return 0;
    }
    
    block->type = BLOCK_MENTION_INDEX;
    block->block.mention_index = ind;
    
    return 1;
}

static int parse_hashtag(struct cursor *cur, struct note_block *block) {
    int c;
    u8 *start = cur->p;
    
    if (!parse_char(cur, '#'))
        return 0;
    
    c = peek_char(cur, 0);
    if (c == -1 || is_whitespace(c) || c == '#') {
        cur->p = start;
        return 0;
    }
    
    consume_until_boundary(cur);
    
    block->type = BLOCK_HASHTAG;
    block->block.str.start = (const char*)(start + 1);
    block->block.str.end = (const char*)cur->p;
    
    return 1;
}

static int add_block(struct note_blocks *blocks, struct note_block block)
{
    if (blocks->num_blocks + 1 >= MAX_BLOCKS)
        return 0;
    
    blocks->blocks[blocks->num_blocks++] = block;
    return 1;
}

static int add_text_block(struct note_blocks *blocks, const u8 *start, const u8 *end)
{
    struct note_block b;
    
    if (start == end)
        return 1;
    
    b.type = BLOCK_TEXT;
    b.block.str.start = (const char*)start;
    b.block.str.end = (const char*)end;
    
    return add_block(blocks, b);
}

static int consume_url_fragment(struct cursor *cur)
{
    int c;

    if ((c = peek_char(cur, 0)) < 0)
        return 1;

    if (c != '#' && c != '?') {
        return 1;
    }

    cur->p++;

    return consume_until_whitespace(cur, 1);
}

static int consume_url_path(struct cursor *cur)
{
    int c;

    if ((c = peek_char(cur, 0)) < 0)
        return 1;

    if (c != '/') {
        return 1;
    }

    while (cur->p < cur->end) {
        c = *cur->p;

        if (c == '?' || c == '#' || is_whitespace(c)) {
            return 1;
        }

        cur->p++;
    }

    return 1;
}

static int consume_url_host(struct cursor *cur)
{
	char c;
	int count = 0;

	while (cur->p < cur->end) {
		c = *cur->p;
		// TODO: handle IDNs
        if (is_alphanumeric(c) || c == '.' || c == '-')
		{
			count++;
			cur->p++;
			continue;
		}

		return count != 0;
	}


	// this means the end of the URL hostname is the end of the buffer and we finished
	return count != 0;
}

static int parse_url(struct cursor *cur, struct note_block *block) {
    u8 *start = cur->p;
    u8 *host;
    int host_len;
    struct cursor path_cur;
    struct nostr_bech32 bech32;
    
    if (!parse_str(cur, "http"))
        return 0;
    
    if (parse_char(cur, 's') || parse_char(cur, 'S')) {
        if (!parse_str(cur, "://")) {
            cur->p = start;
            return 0;
        }
    } else {
        if (!parse_str(cur, "://")) {
            cur->p = start;
            return 0;
        }
    }

    // make sure to save the hostname. We will use this to detect damus.io links
    host = cur->p;

    if (!consume_url_host(cur)) {
	    cur->p = start;
	    return 0;
    }

    // get the length of the host string
    host_len = cur->p - host;

    // save the current parse state so that we can continue from here when
    // parsing the bech32 in the damus.io link if we have it
    copy_cursor(cur, &path_cur);

    // skip leading /
    cursor_skip(&path_cur, 1);

    if (!consume_url_path(cur)) {
	    cur->p = start;
	    return 0;
    }

    if (!consume_url_fragment(cur)) {
	    cur->p = start;
	    return 0;
    }

    // smart parens
    if (start - 1 >= 0 &&
        start < cur->end &&
        *(start - 1) == '(' &&
        (cur->p - 1) < cur->end &&
        *(cur->p - 1) == ')')
    {
        cur->p--;
    }

    // save the bech32 string pos in case we hit a damus.io link
    block->block.str.start = path_cur.p;

    // if we have a damus link, make it a mention
    if (host_len == 8
	&& !strncmp(host, "damus.io", 8)
	&& parse_nostr_bech32(&path_cur, &block->block.mention_bech32.bech32))
    {
	    block->block.str.end = path_cur.p;
	    block->type = BLOCK_MENTION_BECH32;
	    return 1;
    }

    block->type = BLOCK_URL;
    block->block.str.start = (const char *)start;
    block->block.str.end = (const char *)cur->p;
    
    return 1;
}

static int parse_invoice(struct cursor *cur, struct note_block *block) {
    u8 *start, *end;
    char *fail;
    struct bolt11 *bolt11;
    // optional
    parse_str(cur, "lightning:");
    
    start = cur->p;
    
    if (!parse_str(cur, "lnbc"))
        return 0;
    
    if (!consume_until_whitespace(cur, 1)) {
        cur->p = start;
        return 0;
    }
    
    end = cur->p;
    
    char str[end - start + 1];
    str[end - start] = 0;
    memcpy(str, start, end - start);
    
    if (!(bolt11 = bolt11_decode(NULL, str, &fail))) {
        cur->p = start;
        return 0;
    }
    
    block->type = BLOCK_INVOICE;
    
    block->block.invoice.invstr.start = (const char*)start;
    block->block.invoice.invstr.end = (const char*)end;
    block->block.invoice.bolt11 = bolt11;
    
    cur->p = end;
    
    return 1;
}


static int parse_mention_bech32(struct cursor *cur, struct note_block *block) {
    u8 *start = cur->p;
    
    parse_char(cur, '@');
    parse_str(cur, "nostr:");

    block->block.str.start = (const char *)cur->p;
    
    if (!parse_nostr_bech32(cur, &block->block.mention_bech32.bech32)) {
        cur->p = start;
        return 0;
    }
    
    block->block.str.end = (const char *)cur->p;
    
    block->type = BLOCK_MENTION_BECH32;

    return 1;
}

static int add_text_then_block(struct cursor *cur, struct note_blocks *blocks, struct note_block block, u8 **start, const u8 *pre_mention)
{
    if (!add_text_block(blocks, *start, pre_mention))
        return 0;
    
    *start = (u8*)cur->p;
    
    if (!add_block(blocks, block))
        return 0;
    
    return 1;
}

int damus_parse_content(struct note_blocks *blocks, const char *content) {
    int cp, c;
    struct cursor cur;
    struct note_block block;
    u8 *start, *pre_mention;
    
    blocks->words = 0;
    blocks->num_blocks = 0;
    make_cursor((u8*)content, (u8*)content + strlen(content), &cur);
    
    start = cur.p;
    while (cur.p < cur.end && blocks->num_blocks < MAX_BLOCKS) {
        cp = peek_char(&cur, -1);
        c  = peek_char(&cur, 0);
        
        // new word
        if (is_whitespace(cp) && !is_whitespace(c)) {
            blocks->words++;
        }
        
        pre_mention = cur.p;
        if (cp == -1 || is_left_boundary(cp) || c == '#') {
            if (c == '#' && (parse_mention_index(&cur, &block) || parse_hashtag(&cur, &block))) {
                if (!add_text_then_block(&cur, blocks, block, &start, pre_mention))
                    return 0;
                continue;
            } else if ((c == 'h' || c == 'H') && parse_url(&cur, &block)) {
                if (!add_text_then_block(&cur, blocks, block, &start, pre_mention))
                    return 0;
                continue;
            } else if ((c == 'l' || c == 'L') && parse_invoice(&cur, &block)) {
                if (!add_text_then_block(&cur, blocks, block, &start, pre_mention))
                    return 0;
                continue;
            } else if ((c == 'n' || c == '@') && parse_mention_bech32(&cur, &block)) {
                if (!add_text_then_block(&cur, blocks, block, &start, pre_mention))
                    return 0;
                continue;
            }
        }
        
        cur.p++;
    }
    
    if (cur.p - start > 0) {
        if (!add_text_block(blocks, start, cur.p))
            return 0;
    }
    
    return 1;
}

void blocks_init(struct note_blocks *blocks) {
    blocks->blocks = malloc(sizeof(struct note_block) * MAX_BLOCKS);
    blocks->num_blocks = 0;
}

void blocks_free(struct note_blocks *blocks) {
    if (!blocks->blocks) {
        return;
    }
    
    for (int i = 0; i < blocks->num_blocks; ++i) {
        if (blocks->blocks[i].type == BLOCK_MENTION_BECH32) {
            free(blocks->blocks[i].block.mention_bech32.bech32.buffer);
            blocks->blocks[i].block.mention_bech32.bech32.buffer = NULL;
        }
    }

    free(blocks->blocks);
    blocks->num_blocks = 0;
}