#include "osc.h"
#include "../internal.h"
#include <stdlib.h>
#include <string.h>

static int b64_val(char c)
{
    if (c >= 'A' && c <= 'Z') return c - 'A';
    if (c >= 'a' && c <= 'z') return c - 'a' + 26;
    if (c >= '0' && c <= '9') return c - '0' + 52;
    if (c == '+') return 62;
    if (c == '/') return 63;
    return -1;
}

static bool b64_decode(const char *s, size_t n, char *out, size_t *out_len)
{
    size_t pad = 0;
    while (pad < n && s[n - pad - 1] == '=')
        pad++;
    n -= pad;
    if (pad > 2 || (pad && n % 4 + pad != 4))
        return false;
    size_t rem = n % 4;
    if (rem == 1)
        return false;
    size_t i = 0, o = 0;
    for (; i + 4 <= n; i += 4) {
        int a = b64_val(s[i]), b = b64_val(s[i + 1]);
        int c = b64_val(s[i + 2]), d = b64_val(s[i + 3]);
        if ((a | b | c | d) < 0)
            return false;
        out[o++] = (char)(a << 2 | b >> 4);
        out[o++] = (char)(b << 4 | c >> 2);
        out[o++] = (char)(c << 6 | d);
    }
    if (rem >= 2) {
        int a = b64_val(s[i]), b = b64_val(s[i + 1]);
        if ((a | b) < 0)
            return false;
        out[o++] = (char)(a << 2 | b >> 4);
        if (rem == 3) {
            int c = b64_val(s[i + 2]);
            if (c < 0)
                return false;
            out[o++] = (char)(b << 4 | c >> 2);
        }
    }
    *out_len = o;
    return true;
}

void term_osc52(struct term *t, const char *params)
{
    const char *sep = strchr(params, ';');
    if (!sep || sep == params)
        return;
    const char *pd = sep + 1;
    if (!strcmp(pd, "?") || !t->cb.clipboard)
        return;
    size_t sel_len = (size_t)(sep - params);
    char sel[64];
    if (sel_len >= sizeof(sel))
        return;
    memcpy(sel, params, sel_len);
    sel[sel_len] = '\0';
    if (!*pd) {
        t->cb.clipboard(t->cb.ud, sel, "", 0);
        return;
    }
    size_t enc_len = strlen(pd);
    char *dec = (char *)pd;
    size_t dec_len;
    if (b64_decode(pd, enc_len, dec, &dec_len))
        t->cb.clipboard(t->cb.ud, sel, dec, dec_len);
}