import { describe, expect, it } from "vitest";
import { getModel } from "../src/models.js";
import { completeSimple } from "../src/stream.js";

function createLongSystemPrompt(): string {
	const nonce = `${Date.now()}-${Math.random()}`;
	return `You are a concise assistant.\nCache nonce: ${nonce}\n\n${Array(80)
		.fill(
			"Prompt-caching probe content. Keep this exact text stable across requests so the provider can reuse prefix tokens and report cache read and cache write usage.",
		)
		.join("\n\n")}`;
}

describe.skipIf(!process.env.OPENROUTER_API_KEY)("OpenRouter cache_write repro E2E", () => {
	it("regression: preserves cache_write_tokens on openai-completions stream path", {
		retry: 2,
		timeout: 90000,
	}, async () => {
		const model = getModel("openrouter", "google/gemini-2.5-flash");
		const context = {
			systemPrompt: createLongSystemPrompt(),
			messages: [
				{
					role: "user" as const,
					content: "Reply with exactly: OK",
					timestamp: Date.now(),
				},
			],
		};

		const options = {
			apiKey: process.env.OPENROUTER_API_KEY!,
			maxTokens: 32,
			temperature: 0,
			onPayload: (payload: unknown) => {
				const params = payload as {
					messages?: Array<{
						role?: string;
						content?: string | Array<{ type?: string; text?: string; cache_control?: { type: string } }>;
					}>;
				};
				const messages = params.messages;
				if (!Array.isArray(messages)) return payload;

				for (let i = messages.length - 1; i >= 0; i--) {
					const msg = messages[i];
					if (msg.role !== "user") continue;
					if (typeof msg.content === "string") {
						msg.content = [{ type: "text", text: msg.content, cache_control: { type: "ephemeral" } }];
						break;
					}
					if (!Array.isArray(msg.content)) continue;
					for (let j = msg.content.length - 1; j >= 0; j--) {
						const part = msg.content[j];
						if (part.type === "text") {
							part.cache_control = { type: "ephemeral" };
							break;
						}
					}
					break;
				}
				return payload;
			},
		};

		const first = await completeSimple(model, context, options);
		expect(first.stopReason, first.errorMessage).toBe("stop");

		const second = await completeSimple(model, context, options);
		expect(second.stopReason, second.errorMessage).toBe("stop");

		const hasCacheWrite = first.usage.cacheWrite > 0 || second.usage.cacheWrite > 0;
		expect(hasCacheWrite).toBe(true);
	});
});