import type { ExtensionUIContext } from "@mariozechner/pi-coding-agent";
import { visibleWidth, wrapTextWithAnsi } from "@mariozechner/pi-tui";
import {
  applyPanelBackground,
  panelInnerWidth,
  renderKylinPanelBottom,
  renderKylinPanelRow,
  renderKylinPanelTop,
} from "../../../vera-theme/src/public";
import type { Answer, Question } from "./types";

// ── Types ────────────────────────────────────────────────────────────────

type ItemKind = "option" | "confirm" | "write" | "edit" | "submit" | "back";

interface Item {
  kind: ItemKind;
  label: string;
  value?: string;
  checked?: boolean;
}

type PanelResult =
  | { action: "select"; value: string }
  | { action: "toggle"; value: string }
  | { action: "confirm" }
  | { action: "edit-comment" }
  | { action: "submit-comment" }
  | { action: "back" }
  | { action: "cancel" };

// ── Helpers ──────────────────────────────────────────────────────────────

function fmtTitle(i: number, n: number, text: string): string {
  return n > 1 ? `[${i + 1}/${n}] ${text}` : text;
}

function trunc(s: string, max = 35): string {
  return s.length > max ? s.slice(0, max - 1) + "\u2026" : s;
}

// ── Build item list ──────────────────────────────────────────────────────

function buildItems(
  q: Question,
  multi: boolean,
  hasComment: boolean,
  canGoBack: boolean,
  checked: Set<string>,
  comment: string | undefined,
): Item[] {
  const items: Item[] = [];

  for (const o of q.options) {
    items.push({ kind: "option", label: o.label, value: o.value, checked: checked.has(o.value) });
  }

  if (multi) {
    const n = checked.size;
    items.push({ kind: "confirm", label: n > 0 ? `Confirm (${n})` : "Confirm" });
  }

  if (hasComment) {
    if (comment) {
      items.push({ kind: "submit", label: `\u201c${trunc(comment)}\u201d` });
      items.push({ kind: "edit", label: "Edit answer\u2026" });
    } else {
      items.push({ kind: "write", label: "Write your own answer\u2026" });
    }
  }

  if (canGoBack) {
    items.push({ kind: "back", label: "Previous question" });
  }

  return items;
}

// ── Render one item ──────────────────────────────────────────────────────

function renderItem(item: Item, active: boolean, multi: boolean, t: any, maxWidth: number): string[] {
  const cur = active ? t.fg("accent", "\u25b8 ") : "  ";

  switch (item.kind) {
    case "option": {
      let mark = "";
      if (multi) {
        mark = item.checked
          ? t.fg("success", "\u25c6 ")
          : t.fg("dim", "\u25c7 ");
      }
      const prefix = `   ${cur}${mark}`;
      const continuationPrefix = " ".repeat(visibleWidth(prefix));
      const labelWidth = Math.max(1, maxWidth - visibleWidth(prefix));
      const labelLines = wrapTextWithAnsi(item.label, labelWidth);
      const labelColor = active ? "accent" : "text";

      return (labelLines.length > 0 ? labelLines : [""]).map((line, idx) => {
        const linePrefix = idx === 0 ? prefix : continuationPrefix;
        return linePrefix + t.fg(labelColor, line);
      });
    }
    case "confirm": {
      const text = active ? t.fg("success", item.label) : t.fg("muted", item.label);
      return [`   ${cur}${text}`];
    }
    case "submit": {
      const text = active ? t.fg("accent", item.label) : t.fg("muted", item.label);
      return [`   ${cur}${text}`];
    }
    case "write":
    case "edit": {
      const text = active ? t.fg("text", item.label) : t.fg("dim", item.label);
      return [`   ${cur}${text}`];
    }
    case "back": {
      const label = "\u2039 " + item.label;
      const text = active ? t.fg("text", label) : t.fg("dim", label);
      return [`   ${cur}${text}`];
    }
    default:
      return [""];
  }
}

// ── The panel component ──────────────────────────────────────────────────

const WIDGET_KEY = "ask_user";

function stripControlInput(data: string): string {
  return data
    // Bracketed paste wrappers.
    .replace(/^\x1b\[200~/, "")
    .replace(/\x1b\[201~$/, "")
    // Common CSI/SS3 escape sequences.
    .replace(/\x1b\[[0-9;?]*[ -/]*[@-~]/g, "")
    .replace(/\x1bO./g, "")
    // Remaining C0 controls and DEL.
    .replace(/[\x00-\x08\x0b-\x1f\x7f]/g, "");
}

function showPanel(
  ui: ExtensionUIContext,
  title: string,
  q: Question,
  multi: boolean,
  hasComment: boolean,
  canGoBack: boolean,
  checked: Set<string>,
  comment: string | undefined,
  initialCursor: number,
  signal?: AbortSignal,
): Promise<{ result: PanelResult; cursor: number; comment: string | undefined }> {
  return new Promise((resolve) => {
    let currentComment = comment;
    let items = buildItems(q, multi, hasComment, canGoBack, checked, currentComment);
    let cursor = Math.min(initialCursor, items.length - 1);
    let commentMode = false;
    let draft = currentComment ?? "";
    let widgetTui: { requestRender(): void } | undefined;
    let unsubscribeInput: (() => void) | undefined;
    let closed = false;

    const requestRender = () => widgetTui?.requestRender();

    function rebuild(): void {
      items = buildItems(q, multi, hasComment, canGoBack, checked, currentComment);
      if (cursor >= items.length) cursor = items.length - 1;
    }

    function close(result: PanelResult): void {
      if (closed) return;
      closed = true;
      signal?.removeEventListener("abort", onAbort);
      unsubscribeInput?.();
      ui.setWidget(WIDGET_KEY, undefined);
      resolve({ result, cursor, comment: currentComment });
    }

    function onAbort(): void {
      close({ action: "cancel" });
    }

    if (signal?.aborted) {
      close({ action: "cancel" });
      return;
    }
    signal?.addEventListener("abort", onAbort, { once: true });

    function saveDraft(): void {
      currentComment = draft.trim() || undefined;
      commentMode = false;
      rebuild();
      requestRender();
    }

    function cancelDraft(): void {
      draft = currentComment ?? "";
      commentMode = false;
      requestRender();
    }

    function act(): void {
      const it = items[cursor];
      if (!it) return;

      switch (it.kind) {
        case "option":
          if (multi) {
            if (it.value) {
              if (checked.has(it.value)) checked.delete(it.value); else checked.add(it.value);
            }
            rebuild();
            requestRender();
            return;
          }
          close({ action: "select", value: it.value! });
          return;
        case "confirm":
          close({ action: "confirm" });
          return;
        case "write":
        case "edit":
          draft = currentComment ?? "";
          commentMode = true;
          requestRender();
          return;
        case "submit":
          close({ action: "submit-comment" });
          return;
        case "back":
          close({ action: "back" });
          return;
      }
    }

    function handleCommentInput(data: string): boolean {
      if (data === "\x1b" || data === "\x1b\x1b") {
        cancelDraft();
        return true;
      }
      if (data === "\r" || data === "\n") {
        saveDraft();
        return true;
      }
      if (data === "\x7f" || data === "\b") {
        draft = Array.from(draft).slice(0, -1).join("");
        requestRender();
        return true;
      }
      if (data === "\x15") {
        draft = "";
        requestRender();
        return true;
      }
      if (data.startsWith("\x1b")) {
        return true;
      }

      const text = stripControlInput(data);
      if (text) {
        draft += text;
        requestRender();
      }
      return true;
    }

    function handlePanelInput(data: string): boolean {
      if (commentMode) return handleCommentInput(data);

      if (data === "\x1b" || data === "\x1b\x1b") {
        close({ action: "cancel" });
        return true;
      }
      if (data === "\x1b[A" || data === "\x1bOA" || data === "k") { // allow-ansi: keyboard-input
        cursor = cursor === 0 ? items.length - 1 : cursor - 1;
        requestRender();
        return true;
      }
      if (data === "\x1b[B" || data === "\x1bOB" || data === "j") { // allow-ansi: keyboard-input
        cursor = cursor === items.length - 1 ? 0 : cursor + 1;
        requestRender();
        return true;
      }
      if (data === " " && multi && cursor < q.options.length) {
        act();
        return true;
      }
      if (data === "\r" || data === "\n") {
        act();
        return true;
      }
      return false;
    }

    unsubscribeInput = ui.onTerminalInput((data) => {
      if (closed) return undefined;
      return handlePanelInput(data) ? { consume: true } : undefined;
    });

    ui.setWidget(WIDGET_KEY, (tui, theme) => {
      widgetTui = tui;

      return {
        render(width: number): string[] {
          const innerW = panelInnerWidth(width);
          const panelWidth = innerW + 4;
          const out: string[] = [];

          const leftTitle = theme.fg("toolTitle", "Question");
          const right = theme.fg("dim", commentMode ? "answer mode" : `${q.options.length} options`);
          out.push(renderKylinPanelTop(panelWidth, leftTitle, right, theme));

          const titleLines = wrapTextWithAnsi(title, innerW);
          for (const tl of titleLines) {
            out.push(renderKylinPanelRow(theme.fg("mdHeading", tl), panelWidth, theme));
          }
          out.push(renderKylinPanelRow("", panelWidth, theme));

          if (commentMode) {
            const placeholder = q.commentPlaceholder ?? "Enter your answer";
            const inputText = draft
              ? theme.fg("text", draft) + theme.fg("accent", "\u258c")
              : theme.fg("dim", placeholder) + theme.fg("accent", "\u258c");
            out.push(renderKylinPanelRow(theme.fg("muted", "Custom answer"), panelWidth, theme));
            for (const line of wrapTextWithAnsi(inputText, innerW)) {
              out.push(renderKylinPanelRow(line, panelWidth, theme));
            }
            out.push(renderKylinPanelRow("", panelWidth, theme));

            const dot = theme.fg("borderMuted", " \u00b7 ");
            const h = [
              theme.fg("dim", "type") + theme.fg("muted", " answer"),
              theme.fg("dim", "\u232b") + theme.fg("muted", " delete"),
              theme.fg("dim", "\u21b5") + theme.fg("muted", " save"),
              theme.fg("dim", "esc") + theme.fg("muted", " back"),
            ];
            out.push(renderKylinPanelRow(h.join(dot), panelWidth, theme));
          } else {
            const optionCount = q.options.length;
            const itemW = innerW;
            for (let i = 0; i < items.length; i++) {
              if (i === optionCount && items.length > optionCount) {
                out.push(renderKylinPanelRow("", panelWidth, theme));
              }
              for (const line of renderItem(items[i], i === cursor, multi, theme, itemW)) {
                out.push(renderKylinPanelRow(line, panelWidth, theme));
              }
            }

            out.push(renderKylinPanelRow("", panelWidth, theme));

            const dot = theme.fg("borderMuted", " \u00b7 ");
            const h: string[] = [
              theme.fg("dim", "\u2191\u2193") + theme.fg("muted", " move"),
            ];
            if (multi) h.push(theme.fg("dim", "\u2423") + theme.fg("muted", " toggle"));
            h.push(theme.fg("dim", "\u21b5") + theme.fg("muted", " select"));
            h.push(theme.fg("dim", "esc") + theme.fg("muted", " cancel"));
            out.push(renderKylinPanelRow(h.join(dot), panelWidth, theme));
          }

          out.push(renderKylinPanelBottom(panelWidth, theme));

          return applyPanelBackground(out, "pending", theme);
        },

        invalidate(): void {},
      };
    }, { placement: "aboveEditor" });
  });
}

// ── Ask one question ─────────────────────────────────────────────────────

async function askOne(
  ui: ExtensionUIContext,
  q: Question,
  idx: number,
  total: number,
  canGoBack: boolean,
  signal?: AbortSignal,
): Promise<Answer | "back"> {
  const title = fmtTitle(idx, total, q.text);
  const multi = q.type === "multi";
  const hasComment = q.allowComment !== false;
  const checked = new Set<string>();
  let comment: string | undefined;
  let cursor = 0;

  while (true) {
    if (signal?.aborted) return { questionId: q.id, selected: [], skipped: true };

    const panel = await showPanel(
      ui, title, q, multi, hasComment, canGoBack, checked, comment, cursor, signal,
    );
    const { result, cursor: lastCursor } = panel;
    cursor = lastCursor;
    comment = panel.comment;

    switch (result.action) {
      case "select":
        return { questionId: q.id, selected: [result.value], comment, skipped: false };

      case "confirm": {
        const ordered = q.options.filter((o) => checked.has(o.value)).map((o) => o.value);
        return { questionId: q.id, selected: ordered, comment, skipped: ordered.length === 0 && !comment };
      }

      case "submit-comment":
        return { questionId: q.id, selected: [], comment, skipped: false };

      case "edit-comment":
        continue;

      case "back":
        return "back";

      case "cancel":
        return { questionId: q.id, selected: [], skipped: true };
    }
  }
}

// ── Public entry point ───────────────────────────────────────────────────

export async function promptQuestions(
  ui: ExtensionUIContext,
  questions: Question[],
  signal?: AbortSignal,
): Promise<Answer[]> {
  const answers: Answer[] = [];
  let i = 0;

  while (i < questions.length) {
    if (signal?.aborted) break;

    const q = questions[i];
    const result = await askOne(ui, q, i, questions.length, i > 0, signal);

    if (result === "back") { i--; answers.pop(); continue; }
    answers.push(result);
    i++;
  }

  return answers;
}