src/agents/sessions/tools/edit-diff.test.ts

import { describe, expect, it } from "vitest";
import { applyEditsPreservingLineEndings, generateDiffString } from "./edit-diff.js";

function getMismatchMessage(
  content: string,
  edits: Array<{ oldText: string; newText: string }>,
): string {
  try {
    applyEditsPreservingLineEndings(content, edits, "test.ts");
  } catch (error) {
    return error instanceof Error ? error.message : String(error);
  }
  throw new Error("Expected edit mismatch");
}

describe("applyEditsToNormalizedContent", () => {
  it("shows the closest matching line with expected, found, and difference marker", () => {
    const message = getMismatchMessage(
      "line one\nthis is a test line\nanother line here\nconst value = 42;\nfinal line\n",
      [{ oldText: "const value = 99;", newText: "" }],
    );

    expect(message).toMatch(/near line 4 \(\d+% match\)/);
    expect(message).toContain('expected: "const value = 99;"');
    expect(message).toContain('found:    "const value = 42;"');
    expect(message).toMatch(/\^{1,12}/);
  });

  it("shows up to 3 best candidates sorted by similarity", () => {
    const message = getMismatchMessage(
      "function alpha() {}\nfunction beta() {}\nfunction bet() {}\nfunction delta() {}\n",
      [{ oldText: "function betaa() {}", newText: "" }],
    );

    expect(message.match(/near line/g)).toHaveLength(3);
    expect(message.indexOf("near line 2")).toBeLessThan(message.indexOf("near line 3"));
  });

  it("uses the most meaningful oldText line for multiline diagnostics", () => {
    const message = getMismatchMessage("header\nconst actualValue = 42;\nfooter\n", [
      { oldText: "x\nconst actualValue = 99;\n", newText: "" },
    ]);

    expect(message).toContain("near line 2");
    expect(message).toContain('expected: "const actualValue = 99;"');
  });

  it("calls out indentation differences", () => {
    const message = getMismatchMessage("      const value = 42;\n", [
      { oldText: "            const value = 42;", newText: "" },
    ]);

    expect(message).toContain("indentation differs (expected 12 spaces, found 6 spaces)");
  });

  it("calls out escaping differences", () => {
    const message = getMismatchMessage('const pattern = "\\bword\\b";\n', [
      { oldText: 'const pattern = "\\\\bword\\\\b";', newText: "" },
    ]);

    expect(message).toContain("escaping differs (expected 4 backslashes, found 2)");
  });

  it("omits candidates below the similarity threshold", () => {
    const message = getMismatchMessage("abc\nxyz\n123\n", [
      { oldText: "completely different text here", newText: "" },
    ]);

    expect(message).toContain("Could not find the exact text");
    expect(message).not.toContain("Closest matching lines");
  });

  it("bounds candidate scanning and displayed line length", () => {
    const content = `${Array.from({ length: 1000 }, () => "unrelated").join("\n")}\n${"x".repeat(
      200_000,
    )}const value = 42;`;
    const message = getMismatchMessage(content, [{ oldText: "const value = 99;", newText: "" }]);

    expect(message).not.toContain("const value = 42");
    expect(message.length).toBeLessThan(1000);
  });

  it("does not split surrogate pairs at the displayed line boundary", () => {
    const message = getMismatchMessage(`${"x".repeat(119)}🙂found\n`, [
      { oldText: `${"x".repeat(119)}🙂expected`, newText: "" },
    ]);

    expect(message).toContain("Closest matching lines");
    expect(message).not.toContain("\\ud83d");
  });

  it("includes candidate hints for multi-edit failures", () => {
    const message = getMismatchMessage("alpha\nbeta\ngamma\n", [
      { oldText: "alpha", newText: "A" },
      { oldText: "bta", newText: "B" },
    ]);

    expect(message).toMatch(/Could not find edits\[1\][\s\S]*near line 2/);
  });
});

describe("generateDiffString", () => {
  it("numbers context lines from the new file after an insertion", () => {
    const result = generateDiffString(
      "first\nthird\nfourth\n",
      "first\nsecond\nthird\nfourth\n",
      2,
    );

    expect(result).toEqual({
      diff: " 1 first\n+2 second\n 3 third\n 4 fourth",
      firstChangedLine: 2,
    });
  });

  it("numbers context lines from the new file after a deletion", () => {
    const result = generateDiffString(
      "first\nsecond\nthird\nfourth\n",
      "first\nthird\nfourth\n",
      2,
    );

    expect(result).toEqual({
      diff: " 1 first\n-2 second\n 2 third\n 3 fourth",
      firstChangedLine: 2,
    });
  });

  it("separates distant hunks without displaying dependency EOF markers", () => {
    const oldContent = Array.from({ length: 10 }, (_, index) => String(index + 1)).join("\n");
    const newContent = oldContent.replace(/^2$/m, "TWO").replace(/^9$/m, "NINE");

    expect(generateDiffString(oldContent, newContent, 1)).toEqual({
      diff: "  1 1\n- 2 2\n+ 2 TWO\n  3 3\n    ...\n  8 8\n- 9 9\n+ 9 NINE\n 10 10",
      firstChangedLine: 2,
    });
  });
});

describe("applyEditsToNormalizedContent uniqueness", () => {
  it("replaces an exactly unique match when trailing whitespace makes a sibling line fuzzy-identical", () => {
    const content = "foo();  \nfoo();\nbar();\n";

    const result = applyEditsPreservingLineEndings(
      content,
      [{ oldText: "foo();\n", newText: "baz();\n" }],
      "test.ts",
    );

    expect(result.newContent).toBe("foo();  \nbaz();\nbar();\n");
  });
});

describe("fuzzy edit source-span mapping", () => {
  it("preserves escaped Unicode bytes outside a fuzzy-matched span", () => {
    const content =
      "export const RETRY\u00A0MAX = 3; // \u518D\u8A66\u884C\uFF08\u6700\u5927\uFF13\u56DE\uFF09\uFF71\uFF72\uFF73 \u2014 \u8A2D\u5B9A\n" +
      "export const OTHER = 1;\n";

    const result = applyEditsPreservingLineEndings(
      content,
      [{ oldText: "export const RETRY MAX = 3;", newText: "export const RETRY_MAX = 5;" }],
      "config.ts",
    );

    expect(result.finalContent).toBe(
      "export const RETRY_MAX = 5; // \u518D\u8A66\u884C\uFF08\u6700\u5927\uFF13\u56DE\uFF09\uFF71\uFF72\uFF73 \u2014 \u8A2D\u5B9A\n" +
        "export const OTHER = 1;\n",
    );
  });

  it("maps smart-quote folds while preserving a smart-quote comment", () => {
    const content =
      "const label = \u201Chello\u201D; // keep \u201Ccomment\u201D \u2014 unchanged\n";
    const result = applyEditsPreservingLineEndings(
      content,
      [{ oldText: 'const label = "hello";', newText: "const label = 'hi';" }],
      "test.ts",
    );

    expect(result.finalContent).toBe(
      "const label = 'hi'; // keep \u201Ccomment\u201D \u2014 unchanged\n",
    );
  });

  it("allows a match that covers a complete NFKC expansion", () => {
    const result = applyEditsPreservingLineEndings(
      "const value = \uFB01;\n",
      [{ oldText: "fi", newText: "pair" }],
      "test.ts",
    );

    expect(result.finalContent).toBe("const value = pair;\n");
  });

  it("rejects a match ending inside an NFKC expansion", () => {
    expect(() =>
      applyEditsPreservingLineEndings(
        "const value = \uFB01;\n",
        [{ oldText: "f", newText: "x" }],
        "test.ts",
      ),
    ).toThrow(/ambiguous Unicode-normalization or trimmed-whitespace boundary/);
  });

  it("maps a complete combining sequence and preserves supplementary characters", () => {
    const content = "const caf\u0065\u0301 = 1; // \u{1F642}\n";
    const result = applyEditsPreservingLineEndings(
      content,
      [{ oldText: "const caf\u00E9 = 1;", newText: "const cafe = 2;" }],
      "test.ts",
    );

    expect(result.finalContent).toBe("const cafe = 2; // \u{1F642}\n");
  });

  it("preserves trimmed bytes at EOF", () => {
    const result = applyEditsPreservingLineEndings(
      "const value\u00A0= 1;  ",
      [{ oldText: "const value = 1;", newText: "const value = 2;" }],
      "test.ts",
    );

    expect(result.finalContent).toBe("const value = 2;  ");
  });

  it("keeps trim-folding behavior inside a complete fuzzy span", () => {
    const result = applyEditsPreservingLineEndings(
      "before\nfirst  \nsecond\nafter  \n",
      [{ oldText: "first\nsecond", newText: "combined" }],
      "test.ts",
    );

    expect(result.finalContent).toBe("before\ncombined\nafter  \n");
  });

  it("preserves CRLF while mapping a fuzzy Unicode span", () => {
    const result = applyEditsPreservingLineEndings(
      "const value\u00A0= 1;\r\nnext\r\n",
      [{ oldText: "const value = 1;", newText: "const value = 2;" }],
      "test.ts",
    );

    expect(result.finalContent).toBe("const value = 2;\r\nnext\r\n");
  });

  it.each(["fuzzy first", "exact first"])(
    "keeps mixed replacements in original coordinates with %s",
    (order) => {
      const edits = [
        { oldText: "const a = 1;", newText: "const a = 3;" },
        { oldText: "const b = 2;", newText: "const b = 4;" },
      ];
      const result = applyEditsPreservingLineEndings(
        "const a\u00A0= 1;\nconst b = 2;\n",
        order === "exact first" ? edits.toReversed() : edits,
        "test.ts",
      );

      expect(result.finalContent).toBe("const a = 3;\nconst b = 4;\n");
    },
  );
});

describe("applyEditsToNormalizedContent fuzzy uniqueness", () => {
  it("still rejects a fuzzy match that is ambiguous once normalization is applied", () => {
    const content = "foo();  \nfoo();\t\nbar();\n";

    expect(() =>
      applyEditsPreservingLineEndings(
        content,
        [{ oldText: "foo();\n", newText: "baz();\n" }],
        "test.ts",
      ),
    ).toThrow(/Found 2 occurrences/);
  });
});