import { describe, expect, it } from "vitest";
import { DEFAULT_SYSTEM_PROMPT, RECENCY_HINT } from "../lib/constants";
import { buildMessages, composeSystemPrompt } from "../lib/history";
import type { ChatTurn } from "../lib/types";

function turn(prompt: string, response: string): ChatTurn {
  return { id: prompt, prompt, response, thinking: "", model: "m", createdAt: 0, toolCalls: [] };
}

describe("buildMessages", () => {
  it("opens with the system prompt and closes with the new question", () => {
    const messages = buildMessages("SYSTEM", [], "hello");

    expect(messages).toEqual([
      { role: "system", content: "SYSTEM" },
      { role: "user", content: "hello" },
    ]);
  });

  it("replays completed turns in order", () => {
    const messages = buildMessages("SYS", [turn("q1", "a1"), turn("q2", "a2")], "q3");

    expect(messages.map((message) => message.role)).toEqual([
      "system",
      "user",
      "assistant",
      "user",
      "assistant",
      "user",
    ]);
    expect(messages[5]).toEqual({ role: "user", content: "q3" });
  });

  it("skips turns that never produced an answer", () => {
    // A cancelled or failed turn would otherwise be replayed to the model as an
    // empty assistant message, which some models treat as a hard stop.
    const messages = buildMessages("SYS", [turn("q1", ""), turn("q2", "a2")], "q3");

    expect(messages).toHaveLength(4);
    expect(messages[1]).toEqual({ role: "user", content: "q2" });
  });

  it("does not replay tool messages from earlier turns", () => {
    const withTools: ChatTurn = {
      ...turn("q1", "a1"),
      toolCalls: [{ name: "web_search", arguments: {}, result: "a huge page", isError: false }],
    };
    const messages = buildMessages("SYS", [withTools], "q2");

    expect(messages.some((message) => message.role === "tool")).toBe(false);
    expect(JSON.stringify(messages)).not.toContain("a huge page");
  });
});

describe("composeSystemPrompt", () => {
  it("uses the default prompt when the user has not set one", () => {
    expect(composeSystemPrompt("", false)).toBe(DEFAULT_SYSTEM_PROMPT);
  });

  it("prefers the user's prompt when set", () => {
    expect(composeSystemPrompt("Be terse.", false)).toBe("Be terse.");
  });

  it("appends the recency hint only when web tools are on", () => {
    expect(composeSystemPrompt("Be terse.", true)).toBe(`Be terse.\n\n${RECENCY_HINT}`);
    expect(composeSystemPrompt("Be terse.", false)).not.toContain(RECENCY_HINT);
  });
});