#include "termbox.h"

static const unsigned char utf8_length[256] = {
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
    4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 1, 1};

static const unsigned char utf8_mask[6] = {0x7F, 0x1F, 0x0F, 0x07, 0x03, 0x01};

int tb_utf8_char_length(char c) { return utf8_length[(unsigned char)c]; }

int tb_utf8_char_to_unicode(uint32_t *out, const char *c) {
    if (*c == 0)
        return TB_EOF;

    int i;
    unsigned char len = tb_utf8_char_length(*c);
    unsigned char mask = utf8_mask[len - 1];
    uint32_t result = c[0] & mask;
    for (i = 1; i < len; ++i) {
        result <<= 6;
        result |= c[i] & 0x3f;
    }

    *out = result;
    return (int)len;
}

int tb_utf8_unicode_to_char(char *out, uint32_t c) {
    int len = 0;
    int first;
    int i;

    if (c < 0x80) {
        first = 0;
        len = 1;
    } else if (c < 0x800) {
        first = 0xc0;
        len = 2;
    } else if (c < 0x10000) {
        first = 0xe0;
        len = 3;
    } else if (c < 0x200000) {
        first = 0xf0;
        len = 4;
    } else if (c < 0x4000000) {
        first = 0xf8;
        len = 5;
    } else {
        first = 0xfc;
        len = 6;
    }

    for (i = len - 1; i > 0; --i) {
        out[i] = (c & 0x3f) | 0x80;
        c >>= 6;
    }
    out[0] = c | first;

    return len;
}