#include <ctype.h>
#define i_header
#include <stc/cstr.h>
#include "utf8tabs.inc"

// https://news.ycombinator.com/item?id=15423674
// https://gist.github.com/s4y/344a355f8c1f99c6a4cb2347ec4323cc

void utf8_decode(utf8_decode_t *d, const uint8_t b)
{
    switch (d->state) {
    case UTF8_OK:
        if      (b < 0x80) d->codep = b, d->size = 1;
        else if (b < 0xC2) d->state = UTF8_ERROR, d->size = 0;
        else if (b < 0xE0) d->state = 1, d->codep = b & 0x1F, d->size = 2;
        else if (b < 0xF0) d->state = 2, d->codep = b & 0x0F, d->size = 3;
        else if (b < 0xF5) d->state = 3, d->codep = b & 0x07, d->size = 4;
        else d->state = UTF8_ERROR, d->size = 0;
        break;
    case 1: case 2: case 3:
        if ((b & 0xC0) == 0x80) {
            d->state -= 1;
            d->codep = (d->codep << 6) | (b & 0x3F);
        } else
            d->state = UTF8_ERROR, d->size = 0;
    }
}

unsigned utf8_encode(char *out, uint32_t c)
{
    if (c < 0x80U) {
        out[0] = (char) c;
        return 1;
    } else if (c < 0x0800U) {
        out[0] = (char) ((c>>6  & 0x1F) | 0xC0);
        out[1] = (char) ((c     & 0x3F) | 0x80);
        return 2;
    } else if (c < 0x010000U) {
        if ((c < 0xD800U) | (c >= 0xE000U)) {
            out[0] = (char) ((c>>12 & 0x0F) | 0xE0);
            out[1] = (char) ((c>>6  & 0x3F) | 0x80);
            out[2] = (char) ((c     & 0x3F) | 0x80);
            return 3;
        }
    } else if (c < 0x110000U) {
        out[0] = (char) ((c>>18 & 0x07) | 0xF0);
        out[1] = (char) ((c>>12 & 0x3F) | 0x80);
        out[2] = (char) ((c>>6  & 0x3F) | 0x80);
        out[3] = (char) ((c     & 0x3F) | 0x80);
        return 4;
    }
    return 0;
}

void utf8_peek(utf8_decode_t* d, const char *s) {
    utf8_decode(d, (uint8_t)*s++);
    switch (d->size) {
        case 4: utf8_decode(d, (uint8_t)*s++);
        case 3: utf8_decode(d, (uint8_t)*s++);
        case 2: utf8_decode(d, (uint8_t)*s++);
    }
}

bool utf8_valid(const char* s) {
    utf8_decode_t d = {UTF8_OK};
    while (*s)
        utf8_decode(&d, (uint8_t)*s++);
    return d.state == UTF8_OK;
}

bool utf8_valid_n(const char* s, size_t n) {
    utf8_decode_t d = {UTF8_OK};
    while ((n-- != 0) & (*s != 0))
        utf8_decode(&d, (uint8_t)*s++);
    return d.state == UTF8_OK;
}

uint32_t utf8_tolower(uint32_t c) {
    for (size_t i=0; i < sizeof casefold/sizeof *casefold; ++i) {
        if (c <= casefold[i].c1) {
            if (c < casefold[i].c0) return c;
            int d = casefold[i].m1 - casefold[i].c1;
            if (d == 1) return c + ((casefold[i].c1 & 1) == (c & 1));
            return c + d;
        }
    }
    return c;
}

uint32_t utf8_toupper(uint32_t c) {
    for (size_t i=0; i < sizeof cfold_low/sizeof *cfold_low; ++i) {
        struct CaseFold cfold = casefold[cfold_low[i]];
        if (c <= cfold.m1) {
            int d = cfold.m1 - cfold.c1;
            if (c < (uint32_t)(cfold.c0 + d)) return c;
            if (d == 1) return c - ((cfold.m1 & 1) == (c & 1));
            return c - d;
        }
    }
    return c;
}

bool utf8_isupper(uint32_t c) {
    return utf8_tolower(c) != c;
}

bool utf8_islower(uint32_t c) {
    return utf8_toupper(c) != c;
}

bool utf8_isspace(uint32_t c) {
    static uint16_t t[] = {0x20, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x85, 0xA0,
                           0x1680, 0x2028, 0x2029, 0x202F, 0x205F, 0x3000};
    for (size_t i=0; i<sizeof t/sizeof *t; ++i)
        if (c == t[i]) return true;
    return (c >= 0x2000) & (c <= 0x200A);
}

bool utf8_isdigit(uint32_t c) {
    return ((c >= '0') & (c <= '9')) ||
           ((c >= 0xFF10) & (c <= 0xFF19));
}

bool utf8_isxdigit(uint32_t c) {
    static uint16_t t[] = {0x30, 0x39, 0x41, 0x46, 0x61, 0x66, 0xFF10,
                           0xFF19, 0xFF21, 0xFF26, 0xFF41, 0xFF46};
    for (size_t i=1; i<sizeof t/sizeof *t; i += 2)
        if (c <= t[i]) return c >= t[i - 1];
    return false;
}

bool utf8_isalnum(uint32_t c) {
    if (c < 128) return isalnum(c) != 0;
    if ((c >= 0xFF10) & (c <= 0xFF19)) return true;
    return utf8_islower(c) || utf8_isupper(c);
}

bool utf8_isalpha(uint32_t c) {
    if (c < 128) return isalpha(c) != 0;
    return utf8_islower(c) || utf8_isupper(c);
}

static struct fnfold {
    int (*conv_asc)(int);
    uint32_t (*conv_u8)(uint32_t);
}
fn_tolower = {tolower, utf8_tolower},
fn_toupper = {toupper, utf8_toupper};


static cstr cstr_casefold(const cstr* self, struct fnfold fold) {
    csview sv = cstr_sv(self);
    cstr out = cstr_null;
    char *buf = cstr_reserve(&out, sv.size*3/2);
    uint32_t cp; size_t sz = 0;
    utf8_decode_t d = {UTF8_OK};

    for (; *sv.str; sv.str += d.size) {
        utf8_peek(&d, sv.str);
        switch (d.size) {
        case 1:
            buf[sz++] = (char)fold.conv_asc(*sv.str);
            break;
        default:
            cp = fold.conv_u8(d.codep);
            sz += utf8_encode(buf + sz, cp);
        }
    }
    _cstr_set_size(&out, sz);
    cstr_shrink_to_fit(&out);
    return out;
}

cstr cstr_tolower(const cstr* self) {
    return cstr_casefold(self, fn_tolower);
}

cstr cstr_toupper(const cstr* self) {
    return cstr_casefold(self, fn_toupper);
}

void cstr_lowercase(cstr* self) {
    cstr_take(self, cstr_casefold(self, fn_tolower));
}

void cstr_uppercase(cstr* self) {
    cstr_take(self, cstr_casefold(self, fn_toupper));
}