import type { StoredChunk } from "@dispatch/wire";
import { describe, expect, it } from "vitest";
import { createConversationCache } from "./cache";
import type { ConversationCacheIndexEntry, ConversationChunkStore } from "./types";

const chunk = (seq: number, role: "user" | "assistant" = "user"): StoredChunk => ({
	seq,
	role,
	chunk: { type: "text", text: `chunk-${seq}` },
});

/**
 * In-memory fake ConversationChunkStore — the ONLY allowed fake.
 * An outermost edge: simulates the storage port without any real I/O.
 */
function createFakeStore(): ConversationChunkStore {
	const store = new Map<string, StoredChunk[]>();

	return {
		async load(conversationId) {
			return store.get(conversationId) ?? [];
		},

		async append(conversationId, chunks) {
			const existing = store.get(conversationId) ?? [];
			const existingSeqs = new Set(existing.map((c) => c.seq));
			const toAdd = chunks.filter((c) => !existingSeqs.has(c.seq));
			store.set(
				conversationId,
				[...existing, ...toAdd].sort((a, b) => a.seq - b.seq),
			);
		},

		async delete(conversationId) {
			store.delete(conversationId);
		},

		async index() {
			const entries: ConversationCacheIndexEntry[] = [];
			for (const [id, chunks] of store) {
				if (chunks.length === 0) continue;
				let maxSeq = 0;
				for (const c of chunks) {
					if (c.seq > maxSeq) maxSeq = c.seq;
				}
				entries.push({
					conversationId: id,
					chunkCount: chunks.length,
					maxSeq,
				});
			}
			return entries;
		},
	};
}

describe("cache.load", () => {
	it("returns stored chunks", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);
		await store.append("conv-1", [chunk(1), chunk(2)]);
		const result = await cache.load("conv-1");
		expect(result).toEqual([chunk(1), chunk(2)]);
	});

	it("returns empty array for absent conversation", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);
		const result = await cache.load("nonexistent");
		expect(result).toEqual([]);
	});
});

describe("cache.commit", () => {
	it("appends only new chunks", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);
		await store.append("conv-1", [chunk(1), chunk(2)]);

		const merged = await cache.commit("conv-1", [chunk(2), chunk(3)]);
		expect(merged).toEqual([chunk(1), chunk(2), chunk(3)]);

		// Verify store has all chunks
		const stored = await store.load("conv-1");
		expect(stored).toEqual([chunk(1), chunk(2), chunk(3)]);
	});

	it("returns full merged result", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);

		const merged = await cache.commit("conv-1", [chunk(3), chunk(1)]);
		expect(merged).toEqual([chunk(1), chunk(3)]);
	});

	it("is idempotent — re-committing same chunks is a no-op", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);

		await cache.commit("conv-1", [chunk(1), chunk(2)]);
		const merged = await cache.commit("conv-1", [chunk(1), chunk(2)]);
		expect(merged).toEqual([chunk(1), chunk(2)]);

		const stored = await store.load("conv-1");
		expect(stored).toEqual([chunk(1), chunk(2)]);
	});
});

describe("cache.sinceSeq", () => {
	it("returns max seq from cache", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);
		await store.append("conv-1", [chunk(1), chunk(5), chunk(3)]);
		expect(await cache.sinceSeq("conv-1")).toBe(5);
	});

	it("returns 0 for empty conversation", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);
		expect(await cache.sinceSeq("conv-1")).toBe(0);
	});
});

describe("cache.evictIfOverBudget", () => {
	it("deletes selected conversations", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store, { maxChunks: 5 });

		await store.append("a", [chunk(1), chunk(2)]);
		await store.append("b", [chunk(1), chunk(2)]);
		await store.append("c", [chunk(1)]);

		// Total = 5, max = 5, under budget
		const evicted = await cache.evictIfOverBudget(null);
		expect(evicted).toEqual([]);

		// Add more to go over budget
		await store.append("d", [chunk(1), chunk(2), chunk(3)]);
		// Total = 8, max = 5, need to evict 3+ chunks

		const evicted2 = await cache.evictIfOverBudget(null);
		expect(evicted2.length).toBeGreaterThan(0);

		// Verify evicted conversations are deleted
		for (const id of evicted2) {
			expect(await store.load(id)).toEqual([]);
		}
	});

	it("never evicts the active conversation", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store, { maxChunks: 3 });

		await store.append("active", [chunk(1), chunk(2), chunk(3)]);
		await store.append("other", [chunk(1), chunk(2)]);

		// Total = 5, max = 3, need to evict 2+ chunks
		const evicted = await cache.evictIfOverBudget("active");
		expect(evicted).not.toContain("active");
		expect(evicted).toContain("other");
	});

	it("returns empty when under budget", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store, { maxChunks: 100 });

		await store.append("a", [chunk(1)]);
		await store.append("b", [chunk(1)]);

		const evicted = await cache.evictIfOverBudget(null);
		expect(evicted).toEqual([]);
	});
});

describe("cache.delete", () => {
	it("removes the conversation from the store", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);

		await store.append("conv-1", [chunk(1), chunk(2)]);
		await cache.delete("conv-1");

		const stored = await store.load("conv-1");
		expect(stored).toEqual([]);
	});

	it("then load returns []", async () => {
		const store = createFakeStore();
		const cache = createConversationCache(store);

		await cache.commit("conv-1", [chunk(1), chunk(2), chunk(3)]);
		await cache.delete("conv-1");

		const result = await cache.load("conv-1");
		expect(result).toEqual([]);
	});
});