import { existsSync, mkdirSync, readFileSync, rmSync, writeFileSync } from "fs";
import { join } from "path";
import { afterEach, beforeEach, describe, expect, it } from "vitest";
import { SettingsManager } from "../src/core/settings-manager.js";

/**
 * Tests for the fix to a bug where external file changes to arrays were overwritten.
 *
 * The bug scenario was:
 * 1. Pi starts with settings.json containing packages: ["npm:some-pkg"]
 * 2. User externally edits file to packages: []
 * 3. User changes an unrelated setting (e.g., theme) via UI
 * 4. save() would overwrite packages back to ["npm:some-pkg"] from stale in-memory state
 *
 * The fix tracks which fields were explicitly modified during the session, and only
 * those fields override file values during save().
 */
describe("SettingsManager - External Edit Preservation", () => {
  const testDir = join(process.cwd(), "test-settings-bug-tmp");
  const agentDir = join(testDir, "agent");
  const projectDir = join(testDir, "project");

  beforeEach(() => {
    if (existsSync(testDir)) {
      rmSync(testDir, { recursive: true });
    }
    mkdirSync(agentDir, { recursive: true });
    mkdirSync(join(projectDir, ".pi"), { recursive: true });
  });

  afterEach(() => {
    if (existsSync(testDir)) {
      rmSync(testDir, { recursive: true });
    }
  });

  it("should preserve file changes to packages array when changing unrelated setting", async () => {
    const settingsPath = join(agentDir, "settings.json");

    // Initial state: packages has one item
    writeFileSync(
      settingsPath,
      JSON.stringify({
        theme: "dark",
        packages: ["npm:pi-mcp-adapter"],
      }),
    );

    // Pi starts up, loads settings into memory
    const manager = SettingsManager.create(projectDir, agentDir);

    // At this point, globalSettings.packages = ["npm:pi-mcp-adapter"]
    expect(manager.getPackages()).toEqual(["npm:pi-mcp-adapter"]);

    // User externally edits settings.json to remove the package
    const currentSettings = JSON.parse(readFileSync(settingsPath, "utf-8"));
    currentSettings.packages = []; // User wants to remove this!
    writeFileSync(settingsPath, JSON.stringify(currentSettings, null, 2));

    // Verify file was changed
    expect(JSON.parse(readFileSync(settingsPath, "utf-8")).packages).toEqual(
      [],
    );

    // User changes an UNRELATED setting via UI (this triggers save)
    manager.setTheme("light");
    await manager.flush();

    // With the fix, packages should be preserved as [] (not reverted to startup value)
    const savedSettings = JSON.parse(readFileSync(settingsPath, "utf-8"));

    expect(savedSettings.packages).toEqual([]);
    expect(savedSettings.theme).toBe("light");
  });

  it("should preserve file changes to extensions array when changing unrelated setting", async () => {
    const settingsPath = join(agentDir, "settings.json");

    writeFileSync(
      settingsPath,
      JSON.stringify({
        theme: "dark",
        extensions: ["/old/extension.ts"],
      }),
    );

    const manager = SettingsManager.create(projectDir, agentDir);

    // User externally updates extensions
    const currentSettings = JSON.parse(readFileSync(settingsPath, "utf-8"));
    currentSettings.extensions = ["/new/extension.ts"];
    writeFileSync(settingsPath, JSON.stringify(currentSettings, null, 2));

    // Change unrelated setting
    manager.setDefaultThinkingLevel("high");
    await manager.flush();

    const savedSettings = JSON.parse(readFileSync(settingsPath, "utf-8"));

    // With the fix, extensions should be preserved (not reverted to startup value)
    expect(savedSettings.extensions).toEqual(["/new/extension.ts"]);
  });

  it("should preserve external project settings changes when updating unrelated project field", async () => {
    const projectSettingsPath = join(projectDir, ".pi", "settings.json");
    writeFileSync(
      projectSettingsPath,
      JSON.stringify({
        extensions: ["./old-extension.ts"],
        prompts: ["./old-prompt.md"],
      }),
    );

    const manager = SettingsManager.create(projectDir, agentDir);

    const currentProjectSettings = JSON.parse(
      readFileSync(projectSettingsPath, "utf-8"),
    );
    currentProjectSettings.prompts = ["./new-prompt.md"];
    writeFileSync(
      projectSettingsPath,
      JSON.stringify(currentProjectSettings, null, 2),
    );

    manager.setProjectExtensionPaths(["./updated-extension.ts"]);
    await manager.flush();

    const savedProjectSettings = JSON.parse(
      readFileSync(projectSettingsPath, "utf-8"),
    );
    expect(savedProjectSettings.prompts).toEqual(["./new-prompt.md"]);
    expect(savedProjectSettings.extensions).toEqual(["./updated-extension.ts"]);
  });

  it("should let in-memory project changes override external changes for the same project field", async () => {
    const projectSettingsPath = join(projectDir, ".pi", "settings.json");
    writeFileSync(
      projectSettingsPath,
      JSON.stringify({
        extensions: ["./initial-extension.ts"],
      }),
    );

    const manager = SettingsManager.create(projectDir, agentDir);

    const currentProjectSettings = JSON.parse(
      readFileSync(projectSettingsPath, "utf-8"),
    );
    currentProjectSettings.extensions = ["./external-extension.ts"];
    writeFileSync(
      projectSettingsPath,
      JSON.stringify(currentProjectSettings, null, 2),
    );

    manager.setProjectExtensionPaths(["./in-memory-extension.ts"]);
    await manager.flush();

    const savedProjectSettings = JSON.parse(
      readFileSync(projectSettingsPath, "utf-8"),
    );
    expect(savedProjectSettings.extensions).toEqual([
      "./in-memory-extension.ts",
    ]);
  });
});