/**
 * TUI state — the single source-of-truth struct for the TUI interface plus
 * all the types it owns. Mirrors `apps/interfaces/tui/src/state/**`.
 *
 * Design: `AppStateRest` is mutated by `applyAction` and read by the renderer
 * each frame. Everything here is logic-pure (no terminal I/O), so it is
 * unit-testable in Bun.
 */

import { Roles, type Role } from "@zesdex/domain";

/* ── Input state ──────────────────────────────────────────────────── */

/** Which source populated the autocomplete dropdown. */
export const AutocompleteKind = {
  Command: "command",
  FileMention: "file_mention",
} as const;
export type AutocompleteKind = (typeof AutocompleteKind)[keyof typeof AutocompleteKind];

/** Builtin slash-commands recognised by the chat input autocomplete. */
export const COMMANDS: string[] = [
  "/help",
  "/quit",
  "/clear",
  "/login",
  "/login zen",
  "/login openai",
  "/edit",
  "/mcp add",
  "/model",
  "/model ls",
  "/model add",
  "/todo",
  "/usage",
  "/compact",
];

/** The user's input buffer, cursor, history, and autocomplete state. */
export class InputState {
  buffer = "";
  cursor = 0;
  history: string[] = [];
  historyIdx: number | null = null;
  autocompleteCandidates: string[] = [];
  autocompleteIdx = 0;
  autocompleteVisible = false;
  autocompleteKind: AutocompleteKind = AutocompleteKind.Command;
  mentionStart = 0;
  historyFile: string | null = null;

  /** Hide the autocomplete dropdown and clear its state. */
  closeAutocomplete(): void {
    this.autocompleteVisible = false;
    this.autocompleteCandidates = [];
    this.autocompleteIdx = 0;
    this.autocompleteKind = AutocompleteKind.Command;
    this.mentionStart = 0;
  }

  /** Open or refresh the autocomplete dropdown by filtering COMMANDS. */
  openAutocomplete(): void {
    const trimmed = this.buffer.trim();
    if (trimmed.length === 0 || !trimmed.startsWith("/")) {
      this.closeAutocomplete();
      return;
    }
    const prefix = trimmed.toLowerCase();
    this.autocompleteCandidates = COMMANDS.filter((c) => c.startsWith(prefix));
    this.autocompleteKind = AutocompleteKind.Command;
    this.autocompleteIdx = 0;
    this.autocompleteVisible = this.autocompleteCandidates.length > 0;
  }

  /** Find the `@mention` token (if any) immediately before the cursor. */
  mentionQueryAtCursor(): [number, string] | null {
    const beforeCursor = this.buffer.slice(0, this.cursor);
    const atPos = beforeCursor.lastIndexOf("@");
    if (atPos === -1) return null;
    const between = beforeCursor.slice(atPos + 1);
    if (/[\s]/.test(between)) return null;
    const boundaryOk =
      atPos === 0 || /[\s]/.test(beforeCursor[atPos - 1] ?? "") || /\s/.test(beforeCursor[atPos - 1] ?? "");
    if (!boundaryOk) return null;
    return [atPos, between];
  }

  /** Open or refresh the `@file` mention dropdown from `files`. */
  openMentionAutocomplete(files: string[]): void {
    const q = this.mentionQueryAtCursor();
    if (!q) {
      this.closeAutocomplete();
      return;
    }
    const [, query] = q;
    const ql = query.toLowerCase();
    // Simple substring + prefix fuzzy match over the file list.
    const matched = files
      .filter((f) => {
        const fl = f.toLowerCase();
        return fl.includes(ql) || f.replace(/.*\//, "").toLowerCase().startsWith(ql);
      })
      .slice(0, 10);
    this.autocompleteCandidates = matched;
    this.autocompleteKind = AutocompleteKind.FileMention;
    this.mentionStart = q[0];
    this.autocompleteIdx = 0;
    this.autocompleteVisible = matched.length > 0;
  }

  /** Move the autocomplete selection up (false) or down (true). */
  cycleAutocomplete(forward: boolean): void {
    const n = this.autocompleteCandidates.length;
    if (n === 0) return;
    if (forward) {
      this.autocompleteIdx = (this.autocompleteIdx + 1) % n;
    } else {
      this.autocompleteIdx =
        this.autocompleteIdx === 0 ? n - 1 : this.autocompleteIdx - 1;
    }
  }

  /** Accept the currently selected autocomplete candidate. Returns true on success. */
  selectAutocomplete(): boolean {
    const candidate = this.autocompleteCandidates[this.autocompleteIdx];
    if (candidate === undefined || candidate === null) return false;
    if (this.autocompleteKind === AutocompleteKind.Command) {
      this.buffer = candidate;
      this.cursor = this.buffer.length;
    } else {
      if (this.cursor < this.mentionStart || this.mentionStart > this.buffer.length) {
        this.closeAutocomplete();
        return false;
      }
      const replacement = `@${candidate} `;
      this.buffer =
        this.buffer.slice(0, this.mentionStart) + replacement + this.buffer.slice(this.cursor);
      this.cursor = this.mentionStart + replacement.length;
    }
    this.closeAutocomplete();
    return true;
  }

  /** Tab-complete: open dropdown or cycle forward. */
  tabComplete(): void {
    if (this.autocompleteVisible) {
      this.cycleAutocomplete(true);
    } else {
      this.openAutocomplete();
    }
  }

  /** Insert a character at the cursor position. */
  insert(c: string): void {
    this.buffer = this.buffer.slice(0, this.cursor) + c + this.buffer.slice(this.cursor);
    this.cursor += c.length;
  }

  /** Delete the character to the left of the cursor (backspace). */
  deleteLeft(): void {
    if (this.cursor > 0) {
      this.cursor -= 1;
      this.buffer = this.buffer.slice(0, this.cursor) + this.buffer.slice(this.cursor + 1);
    }
  }

  /** Delete the character at the cursor position (forward delete). */
  deleteRight(): void {
    if (this.cursor < this.buffer.length) {
      this.buffer = this.buffer.slice(0, this.cursor) + this.buffer.slice(this.cursor + 1);
    }
  }

  /** Submit the current buffer and return the submitted text. */
  submit(): string {
    const result = this.buffer;
    if (result.length > 0) {
      if (this.history[this.history.length - 1] !== result) {
        this.history.push(result);
      }
      this.historyIdx = null;
    }
    this.buffer = "";
    this.cursor = 0;
    return result;
  }

  /** Navigate backward through input history. */
  historyUp(): void {
    if (this.history.length === 0) return;
    let idx: number;
    if (this.historyIdx !== null && this.historyIdx > 0) {
      idx = this.historyIdx - 1;
    } else if (this.historyIdx === null) {
      idx = this.history.length - 1;
    } else {
      return;
    }
    this.historyIdx = idx;
    this.buffer = this.history[idx] ?? "";
    this.cursor = this.buffer.length;
  }

  /** Navigate forward through input history. */
  historyDown(): void {
    if (this.historyIdx !== null && this.historyIdx < this.history.length - 1) {
      const idx = this.historyIdx + 1;
      this.historyIdx = idx;
      this.buffer = this.history[idx] ?? "";
      this.cursor = this.buffer.length;
    } else if (this.historyIdx !== null) {
      this.historyIdx = null;
      this.buffer = "";
      this.cursor = 0;
    }
    // else nothing to do
  }
}

/* ── Overlay ──────────────────────────────────────────────────────── */

/** Which modal overlay, if any, is currently shown over the main TUI view. */
export const Overlay = {
  None: "none",
  Help: "help",
  Settings: "settings",
  Bash: "bash",
  QuitConfirm: "quit_confirm",
  KeyInput: "key_input",
  Editor: "editor",
  Effort: "effort",
  Mcp: "mcp",
  Todo: "todo",
  Plan: "plan",
  Rewind: "rewind",
  Learning: "learning",
  Usage: "usage",
  Loading: "loading",
  ModelSelector: "model_selector",
  ClearConfirm: "clear_confirm",
  Diff: "diff",
} as const;
export type Overlay = (typeof Overlay)[keyof typeof Overlay];

export function overlayIsActive(overlay: Overlay): boolean {
  return overlay !== Overlay.None;
}

/* ── Editor state ─────────────────────────────────────────────────── */

/** Simple inline editor state for the TUI. */
export class EditorState {
  constructor(
    public path: string,
    public content: string,
    public cursor: number = content.length,
  ) {}

  asString(): string {
    return this.content;
  }

  deleteLeft(): void {
    if (this.cursor > 0) {
      this.cursor -= 1;
      this.content = this.content.slice(0, this.cursor) + this.content.slice(this.cursor + 1);
    }
  }
}

/* ── Misc state ───────────────────────────────────────────────────── */

/** The "miscellaneous" slice of app state. */
export class MiscState {
  overlay: Overlay = Overlay.None;
  toasts: { kind: string; message: string; createdMs: number; ttlMs: number }[] = [];
  lastStalenessSweepMs = 0;
  thinking = false;
  effortLevel = 1;
  selectedIndex = 0;
  editor: EditorState | null = null;
  apiConnected = false;
  tickCount = 0;
  todoContent = "";
  planContent = "";
  lessonRunning = false;
  pendingClipboardCopy: string | null = null;
  diffContent = "";
  diffScroll = 0;

  pushToast(toast: { kind: string; message: string; createdMs: number; ttlMs: number }): void {
    this.toasts.push(toast);
  }

  drainExpiredToasts(nowMs: number): void {
    this.toasts = this.toasts.filter((t) => !(nowMs - t.createdMs >= t.ttlMs));
  }
}

/* ── Scroll state ─────────────────────────────────────────────────── */

/** Viewport scroll state: current offset and visible-line count. */
export class ScrollState {
  offset = 0;
  maxVisible = 30;

  scrollUp(amount: number): void {
    this.offset += amount;
  }
  scrollDown(amount: number): void {
    this.offset = Math.max(0, this.offset - amount);
  }
}

/* ── Transcript ───────────────────────────────────────────────────── */

/** A single transcript entry rendered in the TUI chat pane. */
export interface ChatMessageDisplay {
  role: Role;
  content: string;
  reasoning: string;
  timestamp: number;
}

export function makeChatMessage(role: Role, content: string): ChatMessageDisplay {
  return { role, content, reasoning: "", timestamp: Date.now() };
}

/** Bounded ring of recent chat messages used to render the transcript view. */
export class TranscriptCache {
  messages: ChatMessageDisplay[] = [];
  maxLines: number;
  dirty = true;

  constructor(maxLines = 200) {
    this.maxLines = maxLines;
  }

  push(msg: ChatMessageDisplay): void {
    this.messages.push(msg);
    while (this.messages.length > this.maxLines) {
      this.messages.shift();
    }
    this.dirty = true;
  }

  appendToLast(text: string, isReasoning: boolean): void {
    const msg = this.messages[this.messages.length - 1];
    if (msg && msg.role === Roles.Assistant) {
      if (isReasoning) {
        msg.reasoning += text;
      } else {
        msg.content += text;
      }
      this.dirty = true;
    }
  }
}

/* ── AppStateRest ─────────────────────────────────────────────────── */

/**
 * The single source-of-truth state struct for the TUI interface.
 * Mutated via `applyAction`; read by the renderer every frame.
 */
export interface AppStateRest {
  settings: Record<string, unknown>;
  appConfig: { providers: Record<string, { apiBase?: string; defaultApiKey?: string; apiKeyEnv?: string }> };
  workspaceRoots: string[];
  sessionId: string;
  sessionDir: string;
  memoryDir: string;
  worktreesDir: string;
  transcriptCache: TranscriptCache;
  scroll: ScrollState;
  input: InputState;
  misc: MiscState;
  turnInFlightFlag: { value: boolean };
  abortFlag: { value: boolean };
  dirty: boolean;
  quit: boolean;
  helpText: string;
  displayLinesCache: string[];
  cachedTokenCount: number;
  tokenCountDirty: boolean;
  lastRenderWidth: number;
  cachedMsgCount: number;
  cachedLastStart: number;
  cachedLastLen: number;
  renderWidthAtCache: number;
  mentionFiles: string[];
  pendingSubmit: string | null; // set when a turn should be spawned
}

export const DEFAULT_HELP_TEXT = ` Zesdex TUI — Keyboard Shortcuts

 ─── General ───
  Ctrl+C        Quit confirm
  Ctrl+D        Close overlay
  Ctrl+Y        Copy last assistant message
  Esc           Abort turn / Close overlay
  Tab           Autocomplete

 ─── Navigation ───
  ↑ / ↓         History browse / Overlay navigate
  Ctrl+↑/↓      Scroll transcript
  PgUp / PgDown Scroll transcript
  Enter         Submit / Select autocomplete

 ─── Overlays ───
  /help         Show this help
  /settings     Open settings overlay
  /todo         Open tasks (todo) overlay
  /usage        Open usage statistics
  /bash         Open bash jobs overlay
  /mcp          Open MCP server management
  /model        Open model selector
  /compact      Compact conversation
  /clear        Clear transcript
  /rewind       Rewind conversation history

 ─── Editor Mode ───
  /edit <path>  Open file for inline editing
  Ctrl+S        Save changes
  Esc           Dismiss editor`;

/** Construct fresh TUI state. */
export function createTuiState(
  workspaceRoots: string[],
  sessionDir: string,
  memoryDir: string,
): AppStateRest {
  const sessionId = sessionDir.split(/[/\\]/).filter(Boolean).pop() ?? "";
  const worktreesDir = memoryDir.replace(/[\\/][^\\/]*$/, "") + "/worktrees";
  return {
    settings: { provider: "claude" },
    appConfig: { providers: {} },
    workspaceRoots,
    sessionId,
    sessionDir,
    memoryDir,
    worktreesDir,
    transcriptCache: new TranscriptCache(200),
    scroll: new ScrollState(),
    input: new InputState(),
    misc: new MiscState(),
    turnInFlightFlag: { value: false },
    abortFlag: { value: false },
    dirty: true,
    quit: false,
    helpText: DEFAULT_HELP_TEXT,
    displayLinesCache: [],
    cachedTokenCount: 0,
    tokenCountDirty: true,
    lastRenderWidth: 0,
    cachedMsgCount: 0,
    cachedLastStart: 0,
    cachedLastLen: 0,
    renderWidthAtCache: 0,
    mentionFiles: [],
    pendingSubmit: null,
  };
}

/** Whether an agent turn is currently running. */
export function turnInFlight(state: AppStateRest): boolean {
  return state.turnInFlightFlag.value;
}

/** Append a message to the transcript. */
export function pushTranscript(state: AppStateRest, msg: ChatMessageDisplay): void {
  state.transcriptCache.push(msg);
  state.tokenCountDirty = true;
  state.dirty = true;
}

/** Append text to the last assistant message. */
export function appendToLastTranscript(state: AppStateRest, text: string, isReasoning: boolean): void {
  state.transcriptCache.appendToLast(text, isReasoning);
  if (state.transcriptCache.dirty) state.dirty = true;
}

export function markDirty(state: AppStateRest): void {
  state.dirty = true;
}

export function pushToast(
  state: AppStateRest,
  toast: { kind: string; message: string; createdMs: number; ttlMs: number },
): void {
  state.misc.pushToast(toast);
  state.dirty = true;
}

export function toastInfo(state: AppStateRest, message: string): void {
  pushToast(state, { kind: "info", message, createdMs: Date.now(), ttlMs: 4000 });
}
export function toastSuccess(state: AppStateRest, message: string): void {
  pushToast(state, { kind: "success", message, createdMs: Date.now(), ttlMs: 4000 });
}
export function toastWarning(state: AppStateRest, message: string): void {
  pushToast(state, { kind: "warning", message, createdMs: Date.now(), ttlMs: 4000 });
}
export function toastError(state: AppStateRest, message: string): void {
  pushToast(state, { kind: "error", message, createdMs: Date.now(), ttlMs: 5000 });
}

/** Resolve the base directory of the store (grandparent of the session dir). */
export function storeBaseDir(state: AppStateRest): string {
  return state.sessionDir.replace(/[\\/][^\\/]*[\\/][^\\/]*$/, "");
}