#include "tim.h"

i32 tim_ztrlen(cstr s) {
    if(s == NULL)
        return 0;
    i32 n = strlen(s);
    if(n < 0)
        n = 0;
    return n;
}

i32 tim_bsr8(u8 x) {
#if defined __GNUC__ || defined __clang__
    unsigned int b = x;
    b <<= sizeof(b) * CHAR_BIT - 8;
    b  |= 1 << (sizeof(b) * CHAR_BIT - 9);
    return __builtin_clz(b);
#elif defined _MSC_VER
    unsigned long n = 0;
    unsigned long b = x;
    b <<= sizeof(b) * CHAR_BIT - 8;
    b  |= 1 << (sizeof(b) * CHAR_BIT - 9);
    _BitScanReverse(&n, b);
    return n;
#else
    i32 n = 0;
    for (; n < 8 && !(x & 128); n++, x <<= 1) {}
    return n;
#endif
}


i32 tim_utf8_to_i32(cstr s) {
    s = s ? s : "";
    // use bit magic to mask out leading utf8 1s
    u32 c = s[0] & ((1 << (8 - tim_bsr8(~s[0]))) - 1);
    for (i32 i = 1; s[0] && s[i] && i < 4; i++) {
        c = (c << 6) | (s[i] & 63);
    }
    return (i32)c;
}

i32 tim_utf8_len(cstr s) {
    i32 n = 0;
    for (i32 i = 0; s && s[i]; i++) {
        n += (s[i] & 192) != 128;
    }
    return n;
}

i32 tim_utf8_pos(cstr s, i32 pos) {
    i32 i = 0;
    for (i32 n = 0; pos >= 0 && s && s[i]; i++) {
        n += (s[i] & 192) != 128;
        if (n == pos + 1) {
            return i;
        }
    }
    return i;
}

bool tim_utf8_is_wide_perhaps(const u8* s, i32 n) {
    // Character width depends on character, terminal and font. There is no
    // reliable method, however most frequently used characters are narrow.
    // Zero with characters are ignored, and hope that user input is benign.
    if (n < 3 || s[0] < 225) {
        // u+0000 - u+1000, basic latin - tibetan
        return false;
    } else if (s[0] == 226 && s[1] >= 148 && s[1] < 152) {
        // u+2500 - u+2600 box drawing, block elements, geometric shapes
        return false;
    }
    return true;
}

TimText tim_scan_str(cstr s) {
    if(s == NULL)
        s = "";
    TimText t = {
        .width = 0,
        .lines = (s[0] != 0),
    };
    i32 width = 0;
    for (t.size = 0; s[t.size]; t.size++) {
        char ch      = s[t.size];
        i32  newline = (ch == '\n');
        width = newline ? 0 : width;
        width += (ch & 192) != 128 && (u8)ch > 31;
        t.lines += newline;
        t.width = MAX(t.width, width);
    }
    return t;
}

bool tim_next_line(TimLine* l) {
    if (!l->s || !l->s[0]) {
        return false;
    }
    l->line  = l->s;
    l->size  = 0;
    l->width = 0;
    for (cstr s = l->s; s[0] && s[0] != '\n'; s++) {
        l->size  += 1;
        l->width += (s[0] & 192) != 128 && (u8)s[0] > 31;
    }
    l->s += l->size + !!l->s[l->size];
    return true;
}