#include "fsm.h"
#include <string.h>

const uint8_t CH_HTML_ESCAPE[256] = {
    ['&'] = 1, ['<'] = 1, ['>'] = 1, ['"'] = 1,
};

const uint8_t CH_JSON_ESCAPE[256] = {
    ['"'] = 1, ['\\'] = 1,
    [0x00] = 1, [0x01] = 1, [0x02] = 1, [0x03] = 1,
    [0x04] = 1, [0x05] = 1, [0x06] = 1, [0x07] = 1,
    [0x08] = 1, [0x09] = 1, [0x0A] = 1, [0x0B] = 1,
    [0x0C] = 1, [0x0D] = 1, [0x0E] = 1, [0x0F] = 1,
    [0x10] = 1, [0x11] = 1, [0x12] = 1, [0x13] = 1,
    [0x14] = 1, [0x15] = 1, [0x16] = 1, [0x17] = 1,
    [0x18] = 1, [0x19] = 1, [0x1A] = 1, [0x1B] = 1,
    [0x1C] = 1, [0x1D] = 1, [0x1E] = 1, [0x1F] = 1,
};

/* Inline special + HTML escape; combine with (c & 0x80) in the scan loop. */
const uint8_t CH_SCAN_STOP[256] = {
    ['*'] = 1, ['_'] = 1, ['`'] = 1, ['$'] = 1, ['!'] = 1, ['['] = 1,
    ['&'] = 1, ['<'] = 1, ['>'] = 1, ['\\'] = 1, ['~'] = 1,
};

void fsm_write_begin(sashidown_ctx_t *ctx)
{
    ctx->overflow = 0;
    ctx->write_ptr = ctx->output + ctx->output_len;
    ctx->write_end = ctx->output + ctx->output_cap - 1;
}

void fsm_write_end(sashidown_ctx_t *ctx)
{
    if (ctx->write_ptr)
        ctx->output_len = (size_t)(ctx->write_ptr - ctx->output);
    ctx->write_ptr = NULL;
    ctx->write_end = NULL;
}

int fsm_append(sashidown_ctx_t *ctx, char c)
{
    if (unlikely(ctx->overflow))
        return -1;
    if (ctx->write_ptr) {
        if (unlikely(ctx->write_ptr >= ctx->write_end)) {
            ctx->overflow = 1;
            return -1;
        }
        *ctx->write_ptr++ = c;
        return 0;
    }
    if (unlikely(ctx->output_len + 1 >= ctx->output_cap)) {
        ctx->overflow = 1;
        return -1;
    }
    ctx->output[ctx->output_len++] = c;
    return 0;
}

int fsm_append_len(sashidown_ctx_t *restrict ctx, const char *restrict s, size_t n)
{
    if (n == 0)
        return 0;
    if (unlikely(ctx->overflow))
        return -1;
    if (ctx->write_ptr) {
        if (unlikely(ctx->write_ptr + n > ctx->write_end)) {
            ctx->overflow = 1;
            return -1;
        }
        memcpy(ctx->write_ptr, s, n);
        ctx->write_ptr += n;
        return 0;
    }
    if (unlikely(ctx->output_len + n >= ctx->output_cap)) {
        ctx->overflow = 1;
        return -1;
    }
    memcpy(ctx->output + ctx->output_len, s, n);
    ctx->output_len += n;
    return 0;
}

int fsm_append_str(sashidown_ctx_t *ctx, const char *s)
{
    return fsm_append_len(ctx, s, strlen(s));
}

void fsm_append_fast(sashidown_ctx_t *ctx, char c)
{
    if (unlikely(ctx->overflow)) return;
    if (unlikely(ctx->write_ptr >= ctx->write_end)) {
        ctx->overflow = 1;
        return;
    }
    *ctx->write_ptr++ = c;
}

void fsm_append_len_fast(sashidown_ctx_t *restrict ctx, const char *restrict s, size_t n)
{
    if (n == 0) return;
    if (unlikely(ctx->overflow)) return;
    if (unlikely(ctx->write_ptr + n > ctx->write_end)) {
        ctx->overflow = 1;
        return;
    }
    memcpy(ctx->write_ptr, s, n);
    ctx->write_ptr += n;
}