/**
 * Lightweight line-based terminal renderer for the TUI. Renders the
 * `AppStateRest` transcript, input line, overlay, and status into an array of
 * plain-text + ANSI escaped lines. No external ncurses dependency — outputs
 * raw ANSI sequences that work in any terminal. Conceptually mirrors
 * `apps/interfaces/tui/src/view/**` but simplified to line output.
 */
import { Roles } from "@zesdex/domain";
import type { AppStateRest } from "./state.ts";
import { Overlay } from "./state.ts";

const roleLabel: Record<string, string> = {
  [Roles.User]: "you",
  [Roles.Assistant]: "zesdex",
  [Roles.System]: "system",
  [Roles.Tool]: "tool",
};

/** Render the full TUI frame into an array of lines (with ANSI colours). */
export function renderFrame(state: AppStateRest, height: number, width: number): string[] {
  const lines: string[] = [];

  // Header bar.
  lines.push(renderHeader(state, width));

  // Transcript pane.
  const transcriptLines = renderTranscript(state, width);
  lines.push(...transcriptLines);

  // Padding to fill remaining height.
  const used = lines.length;
  for (let i = used; i < height - 3; i++) {
    lines.push("");
  }

  // Overlay content (if any) replaces the input area.
  if (state.misc.overlay !== Overlay.None) {
    lines.push(renderOverlay(state, width));
  } else {
    lines.push(renderInput(state, width));
  }

  // Status/footer bar.
  lines.push(renderStatus(state, width));

  return lines.slice(0, height);
}

function renderHeader(_state: AppStateRest, width: number): string {
  const title = " zesdex ";
  const pad = Math.max(0, width - title.length);
  return `\x1b[1;44m${title}\x1b[0m${" ".repeat(pad)}`;
}

function renderTranscript(state: AppStateRest, width: number): string[] {
  const out: string[] = [];
  const messages = state.transcriptCache.messages;
  // Honour scroll offset from the bottom like a typical chat TUI.
  const start = Math.max(0, messages.length - 30 - state.scroll.offset);
  for (let i = start; i < messages.length; i++) {
    const m = messages[i];
    if (!m) continue;
    const label = (roleLabel[m.role] ?? m.role).padEnd(8);
    const color = m.role === Roles.User ? "\x1b[36m" : m.role === Roles.System ? "\x1b[33m" : "\x1b[32m";
    out.push(`${color}${label}\x1b[0m ${m.content}`);
    if (m.reasoning) {
      out.push(`  \x1b[2m(reasoning) ${m.reasoning}\x1b[0m`);
    }
  }
  void width;
  return out;
}

function renderInput(state: AppStateRest, width: number): string {
  const prompt = "> ";
  const shown = state.input.buffer.length > width - prompt.length
    ? state.input.buffer.slice(state.input.buffer.length - (width - prompt.length))
    : state.input.buffer;
  let line = `\x1b[1m${prompt}\x1b[0m${shown}`;
  // Append autocomplete hint if visible.
  if (state.input.autocompleteVisible && state.input.autocompleteCandidates[state.input.autocompleteIdx]) {
    const cand = state.input.autocompleteCandidates[state.input.autocompleteIdx];
    line += `  \x1b[2m[tab: ${cand}]\x1b[0m`;
  }
  // Toasts.
  for (const t of state.misc.toasts.slice(-2)) {
    line += `  \x1b[3m(${t.message})\x1b[0m`;
  }
  return line.length > width ? line.slice(0, width) : line;
}

function renderOverlay(state: AppStateRest, width: number): string {
  const name = state.misc.overlay;
  if (name === "diff") {
    const diffLines = state.misc.diffContent.split("\n");
    const from = state.misc.diffScroll;
    return diffLines.slice(from, from + 10).join("\n  ");
  }
  if (name === "quit_confirm") {
    return " \x1b[1;31mQuit?\x1b[0m  (y=yes)  \x1b[2mCtrl+C again / /quit to confirm\x1b[0m";
  }
  if (name === "help") {
    return state.helpText;
  }
  void width;
  return ` \x1b[1mOverlay: ${name}\x1b[0m  \x1b[2m(Esc to close)\x1b[0m`;
}

function renderStatus(state: AppStateRest, width: number): string {
  const left = ` model=${(state.settings as { provider?: string }).provider ?? "?"}`;
  const right = state.turnInFlightFlag.value
    ? " \x1b[5m● running\x1b[0m"
    : " \x1b[2m● idle\x1b[0m";
  const combined = `${left}${right}`;
  return combined.length > width ? combined.slice(0, width) : combined;
}