#ifndef _GNU_SOURCE
#define _GNU_SOURCE /* wcwidth */
#endif

#include "cst_textsel.h"
#include "os_compat.h"

#include <stdlib.h>
#include <string.h>
#include <wctype.h>

int cst_utf8_decode(const char *s, size_t avail, wchar_t *wc, size_t *eaten) {
  unsigned long cp = 0;
  int n;
  if (avail == 0)
    return -1;
  /* os_utf8_decode(), not mbrtowc(): the latter follows setlocale(), which on
   * Windows means the ANSI code page, so UTF-8 text would be decoded as GBK
   * and rendered as mojibake. */
  n = os_utf8_decode(s, avail, &cp);
  if (n <= 0) {
    /* Not a valid sequence: fall back to one raw byte, as before. */
    *wc = (wchar_t)(unsigned char)s[0];
    *eaten = 1;
    return 0;
  }
  *wc = (wchar_t)cp;
  *eaten = (size_t)n;
  return 0;
}

int cst_wcwidth(wchar_t wc) {
#ifdef _WIN32
  unsigned long c = (unsigned long)wc;
  if (c == 0)
    return 0;
  if (c < 32 || (c >= 0x7f && c < 0xa0))
    return -1;
  if (c >= 0x1100 &&
      (c <= 0x115f || c == 0x2329 || c == 0x232a ||
       (c >= 0x2e80 && c <= 0xa4cf && c != 0x303f) ||
       (c >= 0xac00 && c <= 0xd7a3) || (c >= 0xf900 && c <= 0xfaff) ||
       (c >= 0xfe10 && c <= 0xfe19) || (c >= 0xfe30 && c <= 0xfe6f) ||
       (c >= 0xff00 && c <= 0xff60) || (c >= 0xffe0 && c <= 0xffe6) ||
       (c >= 0x20000 && c <= 0x2fffd) || (c >= 0x30000 && c <= 0x3fffd)))
    return 2;
  return 1;
#else
  return wcwidth(wc);
#endif
}

int cst_utf8_width(wchar_t wc) {
  int w = cst_wcwidth(wc);
  if (w < 0)
    return 1;
  return w;
}

size_t cst_ansi_skip(const char *s, size_t n) {
  if (n < 2 || (unsigned char)s[0] != 0x1b)
    return 0;
  if (s[1] == '[') {
    size_t i = 2;
    while (i < n) {
      unsigned char c = (unsigned char)s[i++];
      if (c >= 0x40 && c <= 0x7e)
        return i;
    }
    return 0;
  }
  return 2;
}

void cst_selbuf_free(cst_selbuf_t *b) {
  free(b->s);
  b->s = NULL;
  b->n = b->cap = 0;
}

static int selbuf_put(cst_selbuf_t *b, const char *p, size_t n) {
  if (b->n + n + 1 > b->cap) {
    size_t nc = b->cap ? b->cap * 2 : 256;
    while (nc < b->n + n + 1)
      nc *= 2;
    char *ns = realloc(b->s, nc);
    if (!ns)
      return -1;
    b->s = ns;
    b->cap = nc;
  }
  memcpy(b->s + b->n, p, n);
  b->n += n;
  b->s[b->n] = 0;
  return 0;
}

int cst_selbuf_putc(cst_selbuf_t *b, char c) { return selbuf_put(b, &c, 1); }

/* One drawn character: its bytes in the line and the columns it covers. */
typedef struct {
  size_t off, len;
  int col, width;
  wchar_t wc;
} cell_t;

/* Advances to the next drawn character of line, skipping escapes. */
static int next_cell(const char *line, size_t n, size_t *i, int *col,
                     cell_t *c) {
  while (*i < n) {
    size_t skip = cst_ansi_skip(line + *i, n - *i);
    if (skip) {
      *i += skip;
      continue;
    }
    size_t eaten;
    cst_utf8_decode(line + *i, n - *i, &c->wc, &eaten);
    c->off = *i;
    c->len = eaten;
    c->col = *col;
    c->width = cst_utf8_width(c->wc);
    *i += eaten;
    *col += c->width;
    return 1;
  }
  return 0;
}

int cst_textsel_append(cst_selbuf_t *b, const char *line, int indent, int c1,
                       int c2, int trim) {
  size_t n = line ? strlen(line) : 0, i = 0;
  size_t start = b->n;
  int col = indent;
  cell_t c;
  while (next_cell(line, n, &i, &col, &c)) {
    if (c2 >= 0 && c.col > c2)
      break;
    if (c.width == 0 || c.col + c.width - 1 < c1)
      continue;
    if (selbuf_put(b, line + c.off, c.len) < 0)
      return -1;
  }
  if (trim)
    while (b->n > start && b->s[b->n - 1] == ' ')
      b->s[--b->n] = 0;
  return 0;
}

static int is_word(wchar_t wc) {
  return iswalnum((wint_t)wc) || (wc < 128 && wc && strchr("_-./:@~%+=?&#$", (int)wc));
}

void cst_textsel_snap(const char *line, int indent, int *c1, int *c2) {
  size_t n = line ? strlen(line) : 0, i = 0;
  int x = indent;
  cell_t c;
  while (next_cell(line, n, &i, &x, &c)) {
    if (c.width < 2)
      continue;
    int last = c.col + c.width - 1;
    if (*c1 > c.col && *c1 <= last)
      *c1 = c.col;
    if (*c2 >= c.col && *c2 < last)
      *c2 = last;
  }
}

void cst_textsel_word(const char *line, int indent, int col, int *c1, int *c2) {
  *c1 = *c2 = col;
  size_t n = line ? strlen(line) : 0, i = 0;
  int x = indent;
  cell_t c;
  int run_start = -1, in_run = 0;
  while (next_cell(line, n, &i, &x, &c)) {
    if (c.width == 0)
      continue;
    int word = is_word(c.wc);
    if (word && !in_run)
      run_start = c.col;
    in_run = word;
    if (col >= c.col && col < c.col + c.width) {
      if (!word) {
        *c1 = c.col;
        *c2 = c.col + c.width - 1;
        return;
      }
      *c1 = run_start;
      *c2 = c.col + c.width - 1;
      cell_t d;
      while (next_cell(line, n, &i, &x, &d)) {
        if (d.width == 0)
          continue;
        if (!is_word(d.wc))
          break;
        *c2 = d.col + d.width - 1;
      }
      return;
    }
  }
}