/**
 * session-input-harness.ts — Input injection interface for the live session TUI.
 *
 * Provides a text input area at the bottom of the live session overlay,
 * allowing the user to inject messages into a running agent session.
 */
import {
  type Component,
  matchesKey,
  type TUI,
  truncateToWidth,
} from "@mariozechner/pi-tui";
import type { SessionEventStream } from "../session-events.js";
import type { Theme } from "./agent-widget.js";

/**
 * Input harness component for injecting messages into a running agent session.
 */
export class SessionInputHarness implements Component {
  /** Whether this component has keyboard focus. */
  focused = false;

  private inputBuffer = "";
  private history: string[] = [];
  private historyIndex = -1;
  private closed = false;

  constructor(
    private tui: TUI,
    private events: SessionEventStream,
    private theme: Theme,
    private onClose: () => void,
  ) {}

  // ---- Component Interface ----

  render(width: number): string[] {
    if (this.closed || width < 10) return [];

    const th = this.theme;
    const lines: string[] = [];

    // Separator line
    const sepCount = Math.max(1, width - 2);
    lines.push(th.fg("border", "═".repeat(sepCount)));

    if (this.focused) {
      // Active input mode
      const prompt = "> ";
      const cursor = th.fg("accent", "█"); // static cursor indicator (no blink animation yet)
      const displayText = this.inputBuffer + cursor;
      const promptLine = truncateToWidth(prompt + displayText, width);
      lines.push(promptLine);

      // Hint line
      const hint = "Ctrl+C interrupt · Enter send · ↑↓ history · Esc close";
      lines.push(th.fg("dim", truncateToWidth(hint, width)));
    } else {
      // Inactive: just show hint to focus
      lines.push(th.fg("dim", truncateToWidth("Press Tab to focus input", width)));
      lines.push(""); // spacer to match active height
    }

    return lines;
  }

  handleInput(data: string): void {
    if (this.closed) return;

    // Escape to close the live session
    if (matchesKey(data, "escape")) {
      this.onClose();
      return;
    }

    // Tab to toggle focus
    if (matchesKey(data, "tab")) {
      this.focused = !this.focused;
      this.tui.requestRender();
      return;
    }

    if (!this.focused) return;

    // Enter to send
    if (matchesKey(data, "enter") || matchesKey(data, "return")) {
      const text = this.inputBuffer.trim();
      if (text) {
        this.events.inject(text);
        this.history.push(text);
        this.historyIndex = this.history.length;
        this.inputBuffer = "";
        this.tui.requestRender();
      }
      return;
    }

    // Ctrl+C to interrupt
    if (matchesKey(data, "ctrl+c")) {
      this.events.interrupt();
      this.inputBuffer = "";
      this.tui.requestRender();
      return;
    }

    // Backspace
    if (matchesKey(data, "backspace") || data === "\x7f") {
      this.inputBuffer = this.inputBuffer.slice(0, -1);
      this.tui.requestRender();
      return;
    }

    // Arrow up — history back
    if (matchesKey(data, "up")) {
      if (this.history.length > 0 && this.historyIndex > 0) {
        this.historyIndex--;
        this.inputBuffer = this.history[this.historyIndex] ?? "";
        this.tui.requestRender();
      }
      return;
    }

    // Arrow down — history forward
    if (matchesKey(data, "down")) {
      if (this.historyIndex < this.history.length - 1) {
        this.historyIndex++;
        this.inputBuffer = this.history[this.historyIndex] ?? "";
      } else {
        this.historyIndex = this.history.length;
        this.inputBuffer = "";
      }
      this.tui.requestRender();
      return;
    }

    // Regular character input — currently ASCII-only (printable 0x20-0x7e).
    // TODO: support Unicode multi-byte code points by iterating with for...of or Array.from().
    if (data.length === 1 && data.charCodeAt(0) >= 0x20 && data.charCodeAt(0) <= 0x7e) {
      this.inputBuffer += data;
      this.tui.requestRender();
      return;
    }
  }

  invalidate(): void {
    // No cached state
  }

  dispose(): void {
    this.closed = true;
    this.inputBuffer = "";
    this.history = [];
  }
}