/**
 * KHAELOR
 * File: src/tui/renderer/ansi.ts
 * Description: ANSI escape primitives and pure string-measurement helpers (strip, width, truncate, wrap).
 *
 * Author: Simon-Pierre Boucher
 * Contact: contact@spboucher.ai
 */

export const ESC = "\x1b";
export const CSI = "\x1b[";

/** DEC 2026 synchronized-output frame markers (TUI_DESIGN §1.3). */
export const SYNC_ON = "\x1b[?2026h";
export const SYNC_OFF = "\x1b[?2026l";

export const HIDE_CURSOR = "\x1b[?25l";
export const SHOW_CURSOR = "\x1b[?25h";

export const BRACKETED_PASTE_ON = "\x1b[?2004h";
export const BRACKETED_PASTE_OFF = "\x1b[?2004l";

export const ERASE_LINE = "\x1b[2K";
export const ERASE_DOWN = "\x1b[0J";
export const SGR_RESET = "\x1b[0m";

/** Matches CSI sequences, OSC sequences (BEL or ST terminated), and lone two-byte escapes. */
const ANSI_RE = /\x1b\[[0-9;?]*[ -/]*[@-~]|\x1b\][^\x07\x1b]*(?:\x07|\x1b\\)|\x1b./g;

export function stripAnsi(s: string): string {
  return s.replace(ANSI_RE, "");
}

/**
 * Visible width in terminal columns. Code-point counting: correct for the
 * ASCII/Latin/box-drawing/symbol repertoire KHAELOR emits; East-Asian
 * double-width content may over-run by design in V1 (documented limitation).
 */
export function visibleWidth(s: string): number {
  return [...stripAnsi(s)].length;
}

/**
 * Truncate a (possibly styled) string to `width` visible columns.
 * Escape sequences are preserved; if any styling was emitted before the cut,
 * a reset is appended so truncation never leaks styles into following text.
 */
export function truncateAnsi(s: string, width: number): string {
  if (width <= 0) return "";
  if (visibleWidth(s) <= width) return s;
  let out = "";
  let visible = 0;
  let sawEscape = false;
  let i = 0;
  while (i < s.length && visible < width) {
    if (s[i] === ESC) {
      ANSI_RE.lastIndex = i;
      const m = ANSI_RE.exec(s);
      if (m && m.index === i) {
        out += m[0];
        sawEscape = true;
        i += m[0].length;
        continue;
      }
    }
    const cp = s.codePointAt(i);
    const ch = cp !== undefined ? String.fromCodePoint(cp) : (s[i] as string);
    out += ch;
    visible += 1;
    i += ch.length;
  }
  return sawEscape ? out + SGR_RESET : out;
}

/** Greedy word wrap for plain (unstyled) text; hard-splits words longer than the width. */
export function wrapText(text: string, width: number): string[] {
  const w = Math.max(1, width);
  const out: string[] = [];
  for (const raw of text.split("\n")) {
    if ([...raw].length <= w) {
      out.push(raw);
      continue;
    }
    let line = "";
    for (const word of raw.split(" ")) {
      const candidate = line === "" ? word : line + " " + word;
      if ([...candidate].length <= w) {
        line = candidate;
      } else {
        if (line !== "") out.push(line);
        let rest = word;
        while ([...rest].length > w) {
          out.push([...rest].slice(0, w).join(""));
          rest = [...rest].slice(w).join("");
        }
        line = rest;
      }
    }
    out.push(line);
  }
  return out;
}

/** Pad a (possibly styled) string with spaces to `width` visible columns. */
export function padEndAnsi(s: string, width: number): string {
  const w = visibleWidth(s);
  return w >= width ? s : s + " ".repeat(width - w);
}