import { afterEach, beforeEach, describe, expect, test } from "bun:test";
import * as fs from "node:fs/promises";
import * as os from "node:os";
import * as path from "node:path";
import { computeFileHash, formatHashlineHeader, InMemorySnapshotStore } from "@oh-my-pi/hashline";
import { dropIncompleteLastEdit, EDIT_MODE_STRATEGIES } from "@oh-my-pi/pi-coding-agent/edit";

describe("dropIncompleteLastEdit", () => {
	test("keeps all entries when partialJson is undefined", () => {
		const edits = [{ path: "a" }, { path: "b" }];
		expect(dropIncompleteLastEdit(edits, undefined, "edits")).toEqual(edits);
	});

	test("keeps all entries when the trailing object is closed", () => {
		const edits = [{ path: "a" }, { path: "b" }];
		const partial = '{"edits":[{"path":"a"},{"path":"b"}]}';
		expect(dropIncompleteLastEdit(edits, partial, "edits")).toEqual(edits);
	});

	test("drops the last entry when its closing } has not arrived", () => {
		const edits = [{ path: "a" }, { path: "b" }];
		const partial = '{"edits":[{"path":"a"},{"path":"b"';
		expect(dropIncompleteLastEdit(edits, partial, "edits")).toEqual([{ path: "a" }]);
	});

	test("drops the last entry when a new {} has opened after the last close", () => {
		const edits = [{ path: "a" }, { path: "b" }];
		const partial = '{"edits":[{"path":"a"},{"pat';
		expect(dropIncompleteLastEdit(edits, partial, "edits")).toEqual([{ path: "a" }]);
	});

	test("leaves empty edits alone", () => {
		expect(dropIncompleteLastEdit([], '{"edits":[', "edits")).toEqual([]);
	});
});

describe("hashline streaming preview (multi-section)", () => {
	const strategy = EDIT_MODE_STRATEGIES.hashline;
	const textA = "const a = 1;\nconst b = 2;\n";
	const textB = "export const c = 3;\n";
	let tmpDir: string;
	let fileA: string;
	let fileB: string;
	let snapshots: InMemorySnapshotStore;
	let headerA: string;
	let headerB: string;

	beforeEach(async () => {
		tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "hashline-stream-"));
		fileA = path.join(tmpDir, "a.ts");
		fileB = path.join(tmpDir, "b.ts");
		await Bun.write(fileA, textA);
		await Bun.write(fileB, textB);
		// Snapshot tags are mandatory on every section (preview path mirrors
		// the apply path). Record each file's content under the absolute path
		// the section resolves to, then build tagged headers.
		snapshots = new InMemorySnapshotStore();
		headerA = formatHashlineHeader("a.ts", snapshots.record(fileA, textA));
		headerB = formatHashlineHeader("b.ts", snapshots.record(fileB, textB));
	});

	afterEach(async () => {
		await fs.rm(tmpDir, { recursive: true, force: true });
	});

	const ctx = (cwd: string) => ({ cwd, signal: new AbortController().signal, snapshots });

	test("keeps section A's preview when section B's header just arrived", async () => {
		const input = [headerA, "insert head:", "+// new", headerB].join("\n");
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
		expect(previews).not.toBeNull();
		expect(previews).toHaveLength(1);
		expect(previews?.[0]?.path).toBe("a.ts");
		expect(previews?.[0]?.diff).toBeTruthy();
		expect(previews?.[0]?.error).toBeUndefined();
	});

	test("ignores parse errors from the trailing in-progress section", async () => {
		// `7:bad` has invalid payload — the trailing section is still being typed.
		const input = [headerA, "insert head:", "+// new", headerB, "7:bad"].join("\n");
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
		expect(previews).not.toBeNull();
		expect(previews).toHaveLength(1);
		expect(previews?.[0]?.path).toBe("a.ts");
		expect(previews?.[0]?.diff).toBeTruthy();
	});

	test("renders both sections once each has at least one valid op", async () => {
		const input = [headerA, "insert head:", "+// new a", headerB, "insert head:", "+// new b"].join("\n");
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
		expect(previews).toHaveLength(2);
		expect(previews?.map(p => p.path).sort()).toEqual(["a.ts", "b.ts"]);
		for (const p of previews ?? []) {
			expect(p.diff).toBeTruthy();
			expect(p.error).toBeUndefined();
		}
	});
});

describe("hashline streaming preview (single-op trailing payload)", () => {
	const strategy = EDIT_MODE_STRATEGIES.hashline;
	const text = "const a = 1;\nconst b = 2;\nconst c = 3;\n";
	let tmpDir: string;
	let file: string;
	let snapshots: InMemorySnapshotStore;
	let header: string;

	beforeEach(async () => {
		tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "hashline-stream-single-"));
		file = path.join(tmpDir, "a.ts");
		await Bun.write(file, text);
		snapshots = new InMemorySnapshotStore();
		header = formatHashlineHeader("a.ts", snapshots.record(file, text));
	});

	afterEach(async () => {
		await fs.rm(tmpDir, { recursive: true, force: true });
	});

	const ctx = (cwd: string, isStreaming = true) => ({
		cwd,
		signal: new AbortController().signal,
		snapshots,
		isStreaming,
	});

	test("renders a live diff while the sole payload line is still being typed", async () => {
		// The `+` payload has no trailing newline — the common single-op case
		// the trailing-line trim used to erase, collapsing the preview to a
		// "No changes" error that rendered as a blank box for the whole stream.
		const input = `${header}\nreplace 2..2:\n+const b = 22`;
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
		expect(previews).toHaveLength(1);
		expect(previews?.[0]?.error).toBeUndefined();
		expect(previews?.[0]?.diff).toContain("const b = 22");
	});

	test("does not surface stale hash errors while streaming", async () => {
		const input = "¶a.ts#FFFF\nreplace 2..2:\n+const b = 22";
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
		expect(previews).toHaveLength(1);
		expect(previews?.[0]?.error).toBeUndefined();
		expect(previews?.[0]?.diff).toContain("const b = 22");
	});

	test("final preview accepts a live content hash even when the snapshot store has no history", async () => {
		const liveHeader = formatHashlineHeader("a.ts", computeFileHash(text));
		const input = `${liveHeader}\nreplace 2..2:\n+const b = 22\n`;
		const previews = await strategy.computeDiffPreview(
			{ input } as never,
			{
				cwd: tmpDir,
				signal: new AbortController().signal,
				snapshots: new InMemorySnapshotStore(),
				isStreaming: false,
			} as never,
		);
		expect(previews).toHaveLength(1);
		expect(previews?.[0]?.error).toBeUndefined();
		expect(previews?.[0]?.diff).toContain("const b = 22");
	});

	test("final preview recovers a stale tag from snapshot history", async () => {
		await Bun.write(file, `// external\n${text}`);
		const input = `${header}\nreplace 2..2:\n+const b = 22\n`;
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir, false) as never);
		expect(previews).toHaveLength(1);
		expect(previews?.[0]?.error).toBeUndefined();
		expect(previews?.[0]?.diff).toContain("const b = 22");
	});

	test("surfaces stale hash errors once streaming is complete", async () => {
		const input = "¶a.ts#FFFF\nreplace 2..2:\n+const b = 22\n";
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir, false) as never);
		expect(previews).toHaveLength(1);
		expect(previews?.[0]?.error).toContain("not from this session");
	});

	test("yields no preview (not an error) before the first payload byte arrives", async () => {
		// Op header typed, payload still empty: applyPartialTo drops the
		// payload-less op so nothing changes yet. The preview must report null
		// (preserving any prior frame), never a 'No changes' error that wipes it.
		const input = `${header}\nreplace 2..2:\n`;
		const previews = await strategy.computeDiffPreview({ input } as never, ctx(tmpDir) as never);
		expect(previews).toBeNull();
	});
});

describe("apply_patch streaming preview (trailing partial line)", () => {
	const strategy = EDIT_MODE_STRATEGIES.apply_patch;
	let tmpDir: string;
	let file: string;

	beforeEach(async () => {
		tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "applypatch-stream-"));
		file = path.join(tmpDir, "a.ts");
		await Bun.write(file, "const a = 1;\nconst b = 2;\nconst c = 3;\n");
	});

	afterEach(async () => {
		await fs.rm(tmpDir, { recursive: true, force: true });
	});

	const ctx = (cwd: string, isStreaming: boolean) => ({
		cwd,
		signal: new AbortController().signal,
		isStreaming,
	});

	const buildEnvelope = (body: string) =>
		["*** Begin Patch", "*** Update File: a.ts", "@@", " const a = 1;", body].join("\n");

	test("ignores a half-typed trailing line while streaming", async () => {
		// Trailing line has no `\n` — would render as a flickering partial `+`.
		const partialAdd = buildEnvelope("-const b = 2;\n+const b = 22");
		const streaming = await strategy.computeDiffPreview({ input: partialAdd } as never, ctx(tmpDir, true) as never);
		const final = await strategy.computeDiffPreview({ input: partialAdd } as never, ctx(tmpDir, false) as never);
		const streamingDiff = streaming?.[0]?.diff ?? "";
		const finalDiff = final?.[0]?.diff ?? "";
		expect(streamingDiff).not.toContain("const b = 22");
		expect(finalDiff).toContain("const b = 22");
	});

	test("preserves model's typing order so existing `+added` lines don't reshuffle", async () => {
		// Frame A: model has typed `-b +b22`. Frame B: also typed `-c`. The non-
		// streaming unified diff coalesces removals to the top, which would
		// shift `+const b = 22;` down between frames. The streaming preview
		// must keep it at the same position so the user sees only growth at the
		// bottom.
		const frameA = buildEnvelope("-const b = 2;\n+const b = 22;\n");
		const frameB = buildEnvelope("-const b = 2;\n+const b = 22;\n-const c = 3;\n");
		const a = await strategy.computeDiffPreview({ input: frameA } as never, ctx(tmpDir, true) as never);
		const b = await strategy.computeDiffPreview({ input: frameB } as never, ctx(tmpDir, true) as never);
		const linesA = (a?.[0]?.diff ?? "").split("\n");
		const linesB = (b?.[0]?.diff ?? "").split("\n");
		const posA = linesA.findIndex(l => l.includes("const b = 22;"));
		const posB = linesB.findIndex(l => l.includes("const b = 22;"));
		expect(posA).toBeGreaterThanOrEqual(0);
		expect(posB).toBe(posA);
		// New `-const c = 3;` appears strictly *after* the existing addition.
		const cIdx = linesB.findIndex(l => l.startsWith("-const c"));
		expect(cIdx).toBeGreaterThan(posB);
	});
});