import { assert, assertEquals } from "@std/assert";
import { parseDiff } from "../lib/view/diff.ts";
import { buildDiffDocument, type DiffWorkspace } from "../lib/view/diffdoc.ts";

const NO_WS: DiffWorkspace = { resolve: () => null, read: () => null };

//
// a deleted Markdown file keeps Markdown highlighting
//

Deno.test("buildDiffDocument: a deleted Markdown file (new path /dev/null) highlights as Markdown", () => {
  // A plain `diff -u doc.md /dev/null` has no `diff --git` line, so the new
  // path is /dev/null (absent) while the old path is the .md file. The markdown
  // flag must fall back to the old path; otherwise the removed heading reads as
  // TypeScript and loses its heading structure.
  const diff = `--- doc.md\t2026-06-30 14:00:10
+++ /dev/null\t2026-06-30 14:00:10
@@ -1,6 +0,0 @@
-# Title
-
-Some prose here.
-
-- item one
-- item two
`;
  const model = parseDiff(diff)!;
  // Precondition for the bug: the new path is absent, the old path is the .md.
  assertEquals(
    model.files[0].newPath,
    undefined,
    "deleted file has no new path",
  );
  assertEquals(model.files[0].oldPath, "doc.md", "old path is the .md file");

  const { doc } = buildDiffDocument(diff, model, NO_WS);
  const rawLines = diff.split("\n");
  const headIdx = rawLines.indexOf("-# Title");

  // The heading content past the diff marker is one Markdown heading span, not
  // a soup of TypeScript identifiers.
  const codeSpans = doc.lines[headIdx].spans.filter((s) => s.col >= 1);
  assertEquals(
    codeSpans.map((s) => s.cls),
    ["sectionHeader"],
    `the removed heading is a Markdown section header, got ${
      JSON.stringify(doc.lines[headIdx].spans)
    }`,
  );
  // The marker keeps its removal color.
  assertEquals(doc.lines[headIdx].spans[0].cls, "diffDel", "marker is diffDel");

  // No TypeScript identifier classification leaked onto the removed prose.
  assert(
    !doc.lines.some((l) => l.spans.some((s) => s.cls === "identifier")),
    "no TypeScript identifier spans on a deleted Markdown file",
  );
});

//
// a deleted non-Markdown file is unaffected by the fallback
//

Deno.test("buildDiffDocument: a deleted .ts file (new path /dev/null) stays TypeScript", () => {
  // The old-path fallback must not turn a deleted TypeScript file into
  // Markdown: isMarkdownPath of the .ts old path is false.
  const diff = `--- m.ts\t2026-06-30 14:00:10
+++ /dev/null\t2026-06-30 14:00:10
@@ -1,1 +0,0 @@
-const a = 1;
`;
  const model = parseDiff(diff)!;
  assertEquals(
    model.files[0].newPath,
    undefined,
    "deleted file has no new path",
  );
  assertEquals(model.files[0].oldPath, "m.ts", "old path is the .ts file");

  const { doc } = buildDiffDocument(diff, model, NO_WS);
  const rawLines = diff.split("\n");
  const codeIdx = rawLines.indexOf("-const a = 1;");
  // A TypeScript keyword classification survives, confirming the .ts side is
  // still parsed as TypeScript rather than flattened to Markdown prose.
  const codeSpans = doc.lines[codeIdx].spans.filter((s) => s.col >= 1);
  assert(
    codeSpans.some((s) => s.cls === "storageKeyword"),
    `the removed .ts line keeps a TypeScript keyword span, got ${
      JSON.stringify(doc.lines[codeIdx].spans)
    }`,
  );
});