import { describe, expect, test } from "bun:test";

import { formatDiff, formatNewFileDiff } from "../util/diff.js";

// Strip ANSI codes for easier assertion
const stripAnsi = (str: string) => str.replace(/\x1b\[[0-9;]*m/g, "");

describe("formatDiff", () => {
  test("returns empty string for identical content", () => {
    const result = formatDiff("hello\nworld\n", "hello\nworld\n", "test.ts");
    expect(result).toBe("");
  });

  test("shows single line addition", () => {
    const old = "line1\nline2\nline3";
    const updated = "line1\nline2\nnew line\nline3";
    const result = stripAnsi(formatDiff(old, updated, "test.ts"));
    expect(result).toContain("--- a/test.ts");
    expect(result).toContain("+++ b/test.ts");
    expect(result).toContain("+new line");
    expect(result).not.toContain("-new line");
  });

  test("shows single line removal", () => {
    const old = "line1\nline2\nline3";
    const updated = "line1\nline3";
    const result = stripAnsi(formatDiff(old, updated, "test.ts"));
    expect(result).toContain("-line2");
    expect(result).not.toContain("+line2");
  });

  test("shows line replacement", () => {
    const old = "const x = 1;\nconst y = 2;\nconst z = 3;";
    const updated = "const x = 1;\nconst y = 42;\nconst z = 3;";
    const result = stripAnsi(formatDiff(old, updated, "file.ts"));
    expect(result).toContain("-const y = 2;");
    expect(result).toContain("+const y = 42;");
  });

  test("includes context lines", () => {
    const lines = Array.from({ length: 10 }, (_, i) => `line${i + 1}`);
    const old = lines.join("\n");
    const newLines = [...lines];
    newLines[5] = "CHANGED";
    const updated = newLines.join("\n");
    const result = stripAnsi(formatDiff(old, updated, "ctx.ts"));
    // Should include context before and after the change
    expect(result).toContain(" line4");
    expect(result).toContain(" line5");
    expect(result).toContain("-line6");
    expect(result).toContain("+CHANGED");
    expect(result).toContain(" line7");
    expect(result).toContain(" line8");
  });

  test("handles multi-hunk diffs", () => {
    const lines = Array.from({ length: 20 }, (_, i) => `line${i + 1}`);
    const old = lines.join("\n");
    const newLines = [...lines];
    newLines[2] = "CHANGED_A";
    newLines[17] = "CHANGED_B";
    const updated = newLines.join("\n");
    const result = stripAnsi(formatDiff(old, updated, "multi.ts"));
    expect(result).toContain("-line3");
    expect(result).toContain("+CHANGED_A");
    expect(result).toContain("-line18");
    expect(result).toContain("+CHANGED_B");
    // Should have two @@ hunk headers
    const hunkHeaders = result.match(/@@/g);
    expect(hunkHeaders!.length).toBeGreaterThanOrEqual(4); // 2 hunks, each with @@ ... @@
  });

  test("uses ANSI colors for added/removed lines", () => {
    const old = "old line";
    const updated = "new line";
    const result = formatDiff(old, updated, "test.ts");
    // Red for removed
    expect(result).toContain("\x1b[31m-old line\x1b[0m");
    // Green for added
    expect(result).toContain("\x1b[32m+new line\x1b[0m");
  });

  test("handles empty old content (new file)", () => {
    const result = stripAnsi(formatDiff("", "new content\nline 2", "new.ts"));
    expect(result).toContain("+new content");
    expect(result).toContain("+line 2");
  });

  test("handles empty new content (file deleted)", () => {
    const result = stripAnsi(formatDiff("old content\nline 2", "", "del.ts"));
    expect(result).toContain("-old content");
    expect(result).toContain("-line 2");
  });

  test("uses a full fallback diff for oversized files without truncation markers", () => {
    const old = Array.from({ length: 6 }, (_, i) => `old-${i + 1}`).join("\n");
    const updated = Array.from({ length: 6 }, (_, i) =>
      i === 3 ? "new-4" : `old-${i + 1}`,
    ).join("\n");
    const result = stripAnsi(
      formatDiff(old, updated, "oversized.ts", { maxExactLines: 2 }),
    );

    expect(result).toContain("--- a/oversized.ts");
    expect(result).toContain("+++ b/oversized.ts");
    expect(result).toContain("-old-4");
    expect(result).toContain("+new-4");
    expect(result).not.toContain("Diff too large to display");
  });
});

describe("formatNewFileDiff", () => {
  test("shows all lines as additions", () => {
    const content = "line1\nline2\nline3";
    const result = stripAnsi(formatNewFileDiff(content, "new.ts"));
    expect(result).toContain("--- /dev/null");
    expect(result).toContain("+++ b/new.ts");
    expect(result).toContain("+line1");
    expect(result).toContain("+line2");
    expect(result).toContain("+line3");
  });

  test("truncates long files", () => {
    const lines = Array.from({ length: 50 }, (_, i) => `line${i + 1}`);
    const content = lines.join("\n");
    const result = stripAnsi(formatNewFileDiff(content, "big.ts", 10));
    expect(result).toContain("+line1");
    expect(result).toContain("+line10");
    expect(result).not.toContain("+line11");
    expect(result).toContain("... 40 more lines");
  });

  test("does not truncate short files", () => {
    const content = "a\nb\nc";
    const result = stripAnsi(formatNewFileDiff(content, "small.ts"));
    expect(result).not.toContain("more lines");
  });

  test("allows unbounded output when maxLines is null", () => {
    const lines = Array.from({ length: 50 }, (_, i) => `line${i + 1}`);
    const content = lines.join("\n");
    const result = stripAnsi(formatNewFileDiff(content, "all-lines.ts", null));

    expect(result).toContain("+line1");
    expect(result).toContain("+line50");
    expect(result).not.toContain("more lines");
  });
});