import assert from "node:assert";
import { describe, it } from "node:test";
import type { Terminal as XtermTerminalType } from "@xterm/headless";
import { type Component, TUI } from "../src/tui.js";
import { VirtualTerminal } from "./virtual-terminal.js";

class TestComponent implements Component {
  lines: string[] = [];
  render(_width: number): string[] {
    return this.lines;
  }
  invalidate(): void {}
}

function getCellItalic(
  terminal: VirtualTerminal,
  row: number,
  col: number,
): number {
  const xterm = (terminal as unknown as { xterm: XtermTerminalType }).xterm;
  const buffer = xterm.buffer.active;
  const line = buffer.getLine(buffer.viewportY + row);
  assert.ok(line, `Missing buffer line at row ${row}`);
  const cell = line.getCell(col);
  assert.ok(cell, `Missing cell at row ${row} col ${col}`);
  return cell.isItalic();
}

describe("TUI resize handling", () => {
  it("triggers full re-render when terminal height changes", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["Line 0", "Line 1", "Line 2"];
    tui.start();
    await terminal.flush();

    const initialRedraws = tui.fullRedraws;

    // Resize height
    terminal.resize(40, 15);
    await terminal.flush();

    // Should have triggered a full redraw
    assert.ok(
      tui.fullRedraws > initialRedraws,
      "Height change should trigger full redraw",
    );

    const viewport = terminal.getViewport();
    assert.ok(
      viewport[0]?.includes("Line 0"),
      "Content preserved after height change",
    );

    tui.stop();
  });

  it("triggers full re-render when terminal width changes", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["Line 0", "Line 1", "Line 2"];
    tui.start();
    await terminal.flush();

    const initialRedraws = tui.fullRedraws;

    // Resize width
    terminal.resize(60, 10);
    await terminal.flush();

    // Should have triggered a full redraw
    assert.ok(
      tui.fullRedraws > initialRedraws,
      "Width change should trigger full redraw",
    );

    tui.stop();
  });
});

describe("TUI content shrinkage", () => {
  it("clears empty rows when content shrinks significantly", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    tui.setClearOnShrink(true); // Explicitly enable (may be disabled via env var)
    const component = new TestComponent();
    tui.addChild(component);

    // Start with many lines
    component.lines = [
      "Line 0",
      "Line 1",
      "Line 2",
      "Line 3",
      "Line 4",
      "Line 5",
    ];
    tui.start();
    await terminal.flush();

    const initialRedraws = tui.fullRedraws;

    // Shrink to fewer lines
    component.lines = ["Line 0", "Line 1"];
    tui.requestRender();
    await terminal.flush();

    // Should have triggered a full redraw to clear empty rows
    assert.ok(
      tui.fullRedraws > initialRedraws,
      "Content shrinkage should trigger full redraw",
    );

    const viewport = terminal.getViewport();
    assert.ok(viewport[0]?.includes("Line 0"), "First line preserved");
    assert.ok(viewport[1]?.includes("Line 1"), "Second line preserved");
    // Lines below should be empty (cleared)
    assert.strictEqual(viewport[2]?.trim(), "", "Line 2 should be cleared");
    assert.strictEqual(viewport[3]?.trim(), "", "Line 3 should be cleared");

    tui.stop();
  });

  it("handles shrink to single line", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    tui.setClearOnShrink(true); // Explicitly enable (may be disabled via env var)
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["Line 0", "Line 1", "Line 2", "Line 3"];
    tui.start();
    await terminal.flush();

    // Shrink to single line
    component.lines = ["Only line"];
    tui.requestRender();
    await terminal.flush();

    const viewport = terminal.getViewport();
    assert.ok(viewport[0]?.includes("Only line"), "Single line rendered");
    assert.strictEqual(viewport[1]?.trim(), "", "Line 1 should be cleared");

    tui.stop();
  });

  it("handles shrink to empty", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    tui.setClearOnShrink(true); // Explicitly enable (may be disabled via env var)
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["Line 0", "Line 1", "Line 2"];
    tui.start();
    await terminal.flush();

    // Shrink to empty
    component.lines = [];
    tui.requestRender();
    await terminal.flush();

    const viewport = terminal.getViewport();
    // All lines should be empty
    assert.strictEqual(viewport[0]?.trim(), "", "Line 0 should be cleared");
    assert.strictEqual(viewport[1]?.trim(), "", "Line 1 should be cleared");

    tui.stop();
  });
});

describe("TUI differential rendering", () => {
  it("tracks cursor correctly when content shrinks with unchanged remaining lines", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    // Initial render: 5 identical lines
    component.lines = ["Line 0", "Line 1", "Line 2", "Line 3", "Line 4"];
    tui.start();
    await terminal.flush();

    // Shrink to 3 lines, all identical to before (no content changes in remaining lines)
    component.lines = ["Line 0", "Line 1", "Line 2"];
    tui.requestRender();
    await terminal.flush();

    // cursorRow should be 2 (last line of new content)
    // Verify by doing another render with a change on line 1
    component.lines = ["Line 0", "CHANGED", "Line 2"];
    tui.requestRender();
    await terminal.flush();

    const viewport = terminal.getViewport();
    // Line 1 should show "CHANGED", proving cursor tracking was correct
    assert.ok(
      viewport[1]?.includes("CHANGED"),
      `Expected "CHANGED" on line 1, got: ${viewport[1]}`,
    );

    tui.stop();
  });

  it("renders correctly when only a middle line changes (spinner case)", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    // Initial render
    component.lines = ["Header", "Working...", "Footer"];
    tui.start();
    await terminal.flush();

    // Simulate spinner animation - only middle line changes
    const spinnerFrames = ["|", "/", "-", "\\"];
    for (const frame of spinnerFrames) {
      component.lines = ["Header", `Working ${frame}`, "Footer"];
      tui.requestRender();
      await terminal.flush();

      const viewport = terminal.getViewport();
      assert.ok(
        viewport[0]?.includes("Header"),
        `Header preserved: ${viewport[0]}`,
      );
      assert.ok(
        viewport[1]?.includes(`Working ${frame}`),
        `Spinner updated: ${viewport[1]}`,
      );
      assert.ok(
        viewport[2]?.includes("Footer"),
        `Footer preserved: ${viewport[2]}`,
      );
    }

    tui.stop();
  });

  it("resets styles after each rendered line", async () => {
    const terminal = new VirtualTerminal(20, 6);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["\x1b[3mItalic", "Plain"];
    tui.start();
    await terminal.flush();

    assert.strictEqual(getCellItalic(terminal, 1, 0), 0);
    tui.stop();
  });

  it("renders correctly when first line changes but rest stays same", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["Line 0", "Line 1", "Line 2", "Line 3"];
    tui.start();
    await terminal.flush();

    // Change only first line
    component.lines = ["CHANGED", "Line 1", "Line 2", "Line 3"];
    tui.requestRender();
    await terminal.flush();

    const viewport = terminal.getViewport();
    assert.ok(
      viewport[0]?.includes("CHANGED"),
      `First line changed: ${viewport[0]}`,
    );
    assert.ok(
      viewport[1]?.includes("Line 1"),
      `Line 1 preserved: ${viewport[1]}`,
    );
    assert.ok(
      viewport[2]?.includes("Line 2"),
      `Line 2 preserved: ${viewport[2]}`,
    );
    assert.ok(
      viewport[3]?.includes("Line 3"),
      `Line 3 preserved: ${viewport[3]}`,
    );

    tui.stop();
  });

  it("renders correctly when last line changes but rest stays same", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["Line 0", "Line 1", "Line 2", "Line 3"];
    tui.start();
    await terminal.flush();

    // Change only last line
    component.lines = ["Line 0", "Line 1", "Line 2", "CHANGED"];
    tui.requestRender();
    await terminal.flush();

    const viewport = terminal.getViewport();
    assert.ok(
      viewport[0]?.includes("Line 0"),
      `Line 0 preserved: ${viewport[0]}`,
    );
    assert.ok(
      viewport[1]?.includes("Line 1"),
      `Line 1 preserved: ${viewport[1]}`,
    );
    assert.ok(
      viewport[2]?.includes("Line 2"),
      `Line 2 preserved: ${viewport[2]}`,
    );
    assert.ok(
      viewport[3]?.includes("CHANGED"),
      `Last line changed: ${viewport[3]}`,
    );

    tui.stop();
  });

  it("renders correctly when multiple non-adjacent lines change", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    component.lines = ["Line 0", "Line 1", "Line 2", "Line 3", "Line 4"];
    tui.start();
    await terminal.flush();

    // Change lines 1 and 3, keep 0, 2, 4 the same
    component.lines = ["Line 0", "CHANGED 1", "Line 2", "CHANGED 3", "Line 4"];
    tui.requestRender();
    await terminal.flush();

    const viewport = terminal.getViewport();
    assert.ok(
      viewport[0]?.includes("Line 0"),
      `Line 0 preserved: ${viewport[0]}`,
    );
    assert.ok(
      viewport[1]?.includes("CHANGED 1"),
      `Line 1 changed: ${viewport[1]}`,
    );
    assert.ok(
      viewport[2]?.includes("Line 2"),
      `Line 2 preserved: ${viewport[2]}`,
    );
    assert.ok(
      viewport[3]?.includes("CHANGED 3"),
      `Line 3 changed: ${viewport[3]}`,
    );
    assert.ok(
      viewport[4]?.includes("Line 4"),
      `Line 4 preserved: ${viewport[4]}`,
    );

    tui.stop();
  });

  it("handles transition from content to empty and back to content", async () => {
    const terminal = new VirtualTerminal(40, 10);
    const tui = new TUI(terminal);
    const component = new TestComponent();
    tui.addChild(component);

    // Start with content
    component.lines = ["Line 0", "Line 1", "Line 2"];
    tui.start();
    await terminal.flush();

    let viewport = terminal.getViewport();
    assert.ok(viewport[0]?.includes("Line 0"), "Initial content rendered");

    // Clear to empty
    component.lines = [];
    tui.requestRender();
    await terminal.flush();

    // Add content back - this should work correctly even after empty state
    component.lines = ["New Line 0", "New Line 1"];
    tui.requestRender();
    await terminal.flush();

    viewport = terminal.getViewport();
    assert.ok(
      viewport[0]?.includes("New Line 0"),
      `New content rendered: ${viewport[0]}`,
    );
    assert.ok(
      viewport[1]?.includes("New Line 1"),
      `New content line 1: ${viewport[1]}`,
    );

    tui.stop();
  });
});