/**
 * Property-based tests for storage helpers.
 *
 * **Validates: Requirements 6.1, 6.3, 6.4, 7.3, 7.4, 6.5**
 *
 * Properties tested:
 *   1 — Conversation cap enforcement
 *   2 — Saved response cap enforcement
 *   3 — Saved response idempotency
 *   4 — Conversation title truncation
 *   5 — Saved response sidebar truncation (titleFromMessages ≤ 80 chars)
 *   8 — Conversation restore fidelity
 */

import { describe, it, beforeEach, vi, expect } from "vitest";
import * as fc from "fast-check";
import {
  readConversations,
  writeConversations,
  readSavedResponses,
  writeSavedResponses,
  titleFromMessages,
  savedResponseId,
} from "./storage";
import type { Conversation, Message, SavedResponse, QueryResult } from "../types";

// ---------------------------------------------------------------------------
// In-memory localStorage mock
// ---------------------------------------------------------------------------

class InMemoryStorage implements Storage {
  private store: Record<string, string> = {};

  get length(): number {
    return Object.keys(this.store).length;
  }

  clear(): void {
    this.store = {};
  }

  getItem(key: string): string | null {
    return Object.prototype.hasOwnProperty.call(this.store, key)
      ? this.store[key]
      : null;
  }

  key(index: number): string | null {
    return Object.keys(this.store)[index] ?? null;
  }

  removeItem(key: string): void {
    delete this.store[key];
  }

  setItem(key: string, value: string): void {
    this.store[key] = value;
  }
}

// Install the mock before any imports use localStorage
const mockStorage = new InMemoryStorage();
vi.stubGlobal("localStorage", mockStorage);

// ---------------------------------------------------------------------------
// Arbitraries
// ---------------------------------------------------------------------------

/** ISO 8601 UTC timestamp arbitrary */
const isoTimestamp = fc
  .date({ min: new Date("2020-01-01"), max: new Date("2030-01-01") })
  .map((d) => d.toISOString());

/** Arbitrary Message */
const messageArb: fc.Arbitrary<Message> = fc.record({
  role: fc.constantFrom("user" as const, "assistant" as const),
  content: fc.string({ minLength: 0, maxLength: 500 }),
});

/** Arbitrary QueryResult */
const queryResultArb: fc.Arbitrary<QueryResult> = fc.record({
  citations: fc.array(
    fc.record({
      index: fc.nat(),
      domain: fc.string({ minLength: 1, maxLength: 50 }),
      title: fc.string({ minLength: 1, maxLength: 100 }),
      source_url: fc.option(fc.webUrl(), { nil: undefined }),
      line_num: fc.option(fc.nat(), { nil: undefined }),
    }),
    { maxLength: 5 }
  ),
  domains_searched: fc.array(fc.string({ minLength: 1, maxLength: 50 }), {
    maxLength: 5,
  }),
  sections_retrieved: fc.nat({ max: 20 }),
  timing: fc.dictionary(
    fc.string({ minLength: 1, maxLength: 20 }),
    // Use finite floats that survive JSON round-trip (no -0, NaN, or Infinity)
    fc.float({ noNaN: true, noDefaultInfinity: true }).filter(v => !Object.is(v, -0))
  ),
  token_usage: fc.record({ total_tokens: fc.nat({ max: 10000 }) }),
});

/** Arbitrary Conversation */
const conversationArb: fc.Arbitrary<Conversation> = fc
  .tuple(
    fc.uuid(),
    isoTimestamp,
    isoTimestamp,
    fc.array(messageArb, { maxLength: 10 }),
    fc.array(messageArb, { maxLength: 10 }),
    fc.array(fc.tuple(fc.nat({ max: 20 }), queryResultArb), { maxLength: 5 })
  )
  .map(([id, created_at, last_active_at, messages, history, resultPairs]) => {
    const results: Record<string, QueryResult> = {};
    for (const [idx, result] of resultPairs) {
      results[String(idx)] = result;
    }
    // Derive title from messages (mirrors real usage)
    const userMsg = messages.find((m) => m.role === "user");
    const rawTitle = userMsg?.content ?? "New conversation";
    const title =
      rawTitle.length > 80 ? rawTitle.slice(0, 80) + "\u2026" : rawTitle;
    return { id, title, created_at, last_active_at, messages, history, results };
  });

/** Arbitrary SavedResponse with given conversationId and msgIndex */
const savedResponseArb = (
  conversationId: string,
  msgIndex: number
): fc.Arbitrary<SavedResponse> =>
  fc
    .tuple(
      fc.string({ minLength: 1, maxLength: 200 }),
      fc.string({ minLength: 1, maxLength: 2000 }),
      isoTimestamp,
      fc.string({ minLength: 1, maxLength: 80 }),
      fc.array(messageArb, { minLength: 2, maxLength: 2 }),
      fc.array(messageArb, { minLength: 2, maxLength: 2 }),
      queryResultArb
    )
    .map(
      ([
        question,
        answer,
        saved_at,
        source_conversation_title,
        messages_pair,
        history_pair,
        result,
      ]) => ({
        id: savedResponseId(conversationId, msgIndex),
        question,
        answer,
        saved_at,
        source_conversation_id: conversationId,
        source_conversation_title,
        msg_index: msgIndex,
        messages_pair,
        history_pair,
        result,
      })
    );

/** Arbitrary SavedResponse with random conversationId and msgIndex */
const anySavedResponseArb: fc.Arbitrary<SavedResponse> = fc
  .tuple(fc.uuid(), fc.nat({ max: 100 }))
  .chain(([convId, msgIdx]) => savedResponseArb(convId, msgIdx));

// ---------------------------------------------------------------------------
// Setup
// ---------------------------------------------------------------------------

beforeEach(() => {
  mockStorage.clear();
});

// ---------------------------------------------------------------------------
// Property 1: Conversation cap enforcement
// ---------------------------------------------------------------------------

describe("Property 1: Conversation cap enforcement", () => {
  /**
   * **Validates: Requirements 6.3**
   *
   * For any sequence of conversation saves, hmc-conversations length ≤ 20
   * and the evicted entry always has the minimum last_active_at.
   */
  it("hmc-conversations never exceeds 20 entries and evicts the oldest", () => {
    fc.assert(
      fc.property(
        fc.array(conversationArb, { minLength: 1, maxLength: 40 }),
        (conversations) => {
          mockStorage.clear();
          writeConversations(conversations);
          const stored = readConversations();

          // Cap is enforced
          expect(stored.length).toBeLessThanOrEqual(20);

          // If we had more than 20, the stored set must not contain the
          // entry with the globally minimum last_active_at (it was evicted).
          if (conversations.length > 20) {
            const minTs = Math.min(
              ...conversations.map((c) =>
                new Date(c.last_active_at).getTime()
              )
            );
            const storedIds = new Set(stored.map((c) => c.id));
            const evictedCandidates = conversations.filter(
              (c) => new Date(c.last_active_at).getTime() === minTs
            );
            // At least one of the minimum-timestamp entries must be absent
            // (it was evicted). We only check when there's a unique minimum.
            const uniqueMin = evictedCandidates.length === 1;
            if (uniqueMin) {
              expect(storedIds.has(evictedCandidates[0].id)).toBe(false);
            }
          }
        }
      )
    );
  });

  it("stored conversations are sorted by last_active_at descending", () => {
    fc.assert(
      fc.property(
        fc.array(conversationArb, { minLength: 2, maxLength: 30 }),
        (conversations) => {
          mockStorage.clear();
          writeConversations(conversations);
          const stored = readConversations();

          for (let i = 1; i < stored.length; i++) {
            const prev = new Date(stored[i - 1].last_active_at).getTime();
            const curr = new Date(stored[i].last_active_at).getTime();
            expect(prev).toBeGreaterThanOrEqual(curr);
          }
        }
      )
    );
  });
});

// ---------------------------------------------------------------------------
// Property 2: Saved response cap enforcement
// ---------------------------------------------------------------------------

describe("Property 2: Saved response cap enforcement", () => {
  /**
   * **Validates: Requirements 7.4**
   *
   * For any sequence of saved-response saves, hmc-saved-responses length ≤ 50
   * and eviction is by oldest saved_at.
   */
  it("hmc-saved-responses never exceeds 50 entries and evicts the oldest", () => {
    fc.assert(
      fc.property(
        fc.array(anySavedResponseArb, { minLength: 1, maxLength: 80 }),
        (responses) => {
          mockStorage.clear();
          writeSavedResponses(responses);
          const stored = readSavedResponses();

          // Cap is enforced
          expect(stored.length).toBeLessThanOrEqual(50);

          // If we had more than 50, the entry with the globally minimum
          // saved_at must have been evicted.
          if (responses.length > 50) {
            const minTs = Math.min(
              ...responses.map((r) => new Date(r.saved_at).getTime())
            );
            const storedIds = new Set(stored.map((r) => r.id));
            const evictedCandidates = responses.filter(
              (r) => new Date(r.saved_at).getTime() === minTs
            );
            const uniqueMin = evictedCandidates.length === 1;
            if (uniqueMin) {
              expect(storedIds.has(evictedCandidates[0].id)).toBe(false);
            }
          }
        }
      )
    );
  });

  it("stored saved responses are sorted by saved_at descending", () => {
    fc.assert(
      fc.property(
        fc.array(anySavedResponseArb, { minLength: 2, maxLength: 60 }),
        (responses) => {
          mockStorage.clear();
          writeSavedResponses(responses);
          const stored = readSavedResponses();

          for (let i = 1; i < stored.length; i++) {
            const prev = new Date(stored[i - 1].saved_at).getTime();
            const curr = new Date(stored[i].saved_at).getTime();
            expect(prev).toBeGreaterThanOrEqual(curr);
          }
        }
      )
    );
  });
});

// ---------------------------------------------------------------------------
// Property 3: Saved response idempotency
// ---------------------------------------------------------------------------

describe("Property 3: Saved response idempotency", () => {
  /**
   * **Validates: Requirements 7.3**
   *
   * Saving the same (conversation_id, msg_index) pair multiple times results
   * in exactly one record per pair. The upsert pattern: filter out existing
   * record by id, then prepend the new one.
   */
  it("saving the same (conversationId, msgIndex) pair multiple times yields exactly one record", () => {
    fc.assert(
      fc.property(
        fc.uuid(),
        fc.nat({ max: 100 }),
        fc.integer({ min: 2, max: 5 }),
        (conversationId, msgIndex, saveCount) => {
          mockStorage.clear();

          const id = savedResponseId(conversationId, msgIndex);

          // Simulate saving the same pair `saveCount` times (upsert pattern)
          for (let i = 0; i < saveCount; i++) {
            const existing = readSavedResponses();
            // Upsert: remove any existing record with the same id, then add new
            const withoutDuplicate = existing.filter((r) => r.id !== id);
            const newResponse: SavedResponse = {
              id,
              question: `Question version ${i}`,
              answer: `Answer version ${i}`,
              saved_at: new Date(Date.now() + i * 1000).toISOString(),
              source_conversation_id: conversationId,
              source_conversation_title: "Test conversation",
              msg_index: msgIndex,
              messages_pair: [
                { role: "user", content: `Q${i}` },
                { role: "assistant", content: `A${i}` },
              ],
              history_pair: [
                { role: "user", content: `Q${i}` },
                { role: "assistant", content: `A${i}` },
              ],
              result: {
                citations: [],
                domains_searched: [],
                sections_retrieved: 0,
                timing: {},
                token_usage: { total_tokens: 0 },
              },
            };
            writeSavedResponses([newResponse, ...withoutDuplicate]);
          }

          const stored = readSavedResponses();
          const matchingRecords = stored.filter((r) => r.id === id);
          expect(matchingRecords).toHaveLength(1);
        }
      )
    );
  });

  it("multiple distinct (conversationId, msgIndex) pairs each produce exactly one record", () => {
    fc.assert(
      fc.property(
        fc.array(
          fc.tuple(fc.uuid(), fc.nat({ max: 50 })),
          { minLength: 1, maxLength: 10 }
        ),
        (pairs) => {
          mockStorage.clear();

          // Deduplicate pairs by id to avoid intentional collisions in the input
          const seen = new Set<string>();
          const uniquePairs = pairs.filter(([convId, msgIdx]) => {
            const id = savedResponseId(convId, msgIdx);
            if (seen.has(id)) return false;
            seen.add(id);
            return true;
          });

          // Save each pair twice
          for (const [convId, msgIdx] of uniquePairs) {
            const id = savedResponseId(convId, msgIdx);
            for (let i = 0; i < 2; i++) {
              const existing = readSavedResponses();
              const withoutDuplicate = existing.filter((r) => r.id !== id);
              const newResponse: SavedResponse = {
                id,
                question: `Q${i}`,
                answer: `A${i}`,
                saved_at: new Date().toISOString(),
                source_conversation_id: convId,
                source_conversation_title: "Test",
                msg_index: msgIdx,
                messages_pair: [
                  { role: "user", content: "q" },
                  { role: "assistant", content: "a" },
                ],
                history_pair: [
                  { role: "user", content: "q" },
                  { role: "assistant", content: "a" },
                ],
                result: {
                  citations: [],
                  domains_searched: [],
                  sections_retrieved: 0,
                  timing: {},
                  token_usage: { total_tokens: 0 },
                },
              };
              writeSavedResponses([newResponse, ...withoutDuplicate]);
            }
          }

          const stored = readSavedResponses();
          for (const [convId, msgIdx] of uniquePairs) {
            const id = savedResponseId(convId, msgIdx);
            const matches = stored.filter((r) => r.id === id);
            expect(matches).toHaveLength(1);
          }
        }
      )
    );
  });
});

// ---------------------------------------------------------------------------
// Property 4: Conversation title truncation
// ---------------------------------------------------------------------------

describe("Property 4: Conversation title truncation", () => {
  /**
   * **Validates: Requirements 6.4**
   *
   * For any user message string, the derived title is ≤ 80 characters,
   * and if the original exceeds 80 chars the title ends with '…' (U+2026).
   */
  it("title length is always ≤ 80 characters (excluding ellipsis)", () => {
    fc.assert(
      fc.property(fc.string({ minLength: 0, maxLength: 200 }), (content) => {
        const messages: Message[] = [{ role: "user", content }];
        const title = titleFromMessages(messages);

        if (content.length > 80) {
          // Title is the 80-char slice + ellipsis = 81 chars total
          expect(title.length).toBe(81);
          expect(title.endsWith("\u2026")).toBe(true);
          expect(title.slice(0, 80)).toBe(content.slice(0, 80));
        } else {
          expect(title).toBe(content);
          expect(title.length).toBeLessThanOrEqual(80);
        }
      })
    );
  });

  it("ellipsis is present iff original content exceeds 80 characters", () => {
    fc.assert(
      fc.property(fc.string({ minLength: 0, maxLength: 200 }), (content) => {
        const messages: Message[] = [{ role: "user", content }];
        const title = titleFromMessages(messages);

        const hasEllipsis = title.endsWith("\u2026");
        expect(hasEllipsis).toBe(content.length > 80);
      })
    );
  });

  it("returns 'New conversation' when no user message is present", () => {
    fc.assert(
      fc.property(
        fc.array(
          fc.record({
            role: fc.constant("assistant" as const),
            content: fc.string(),
          }),
          { maxLength: 5 }
        ),
        (messages) => {
          const title = titleFromMessages(messages);
          expect(title).toBe("New conversation");
        }
      )
    );
  });
});

// ---------------------------------------------------------------------------
// Property 5: Saved response sidebar truncation
// ---------------------------------------------------------------------------

describe("Property 5: Saved response sidebar truncation (titleFromMessages)", () => {
  /**
   * **Validates: Requirements 8.3**
   *
   * For any user message string exceeding 80 characters, titleFromMessages
   * truncates to exactly 80 chars + ellipsis (total 81 chars).
   * The sidebar display truncation to ±5 chars is tested in task 10.2.
   */
  it("truncated title is exactly 81 chars (80 content + ellipsis) when original > 80", () => {
    fc.assert(
      fc.property(
        fc.string({ minLength: 81, maxLength: 300 }),
        (content) => {
          const messages: Message[] = [{ role: "user", content }];
          const title = titleFromMessages(messages);

          // The truncated title is exactly 80 chars of content + 1 ellipsis char
          expect(title.length).toBe(81);
          expect(title.endsWith("\u2026")).toBe(true);
        }
      )
    );
  });

  it("title displayed length is within [75, 85] when original exceeds 80 characters", () => {
    fc.assert(
      fc.property(
        fc.string({ minLength: 81, maxLength: 300 }),
        (content) => {
          const messages: Message[] = [{ role: "user", content }];
          const title = titleFromMessages(messages);

          // The title (80 chars + ellipsis = 81 chars) is within the [75, 85] window
          expect(title.length).toBeGreaterThanOrEqual(75);
          expect(title.length).toBeLessThanOrEqual(85);
        }
      )
    );
  });
});

// ---------------------------------------------------------------------------
// Property 8: Conversation restore fidelity
// ---------------------------------------------------------------------------

describe("Property 8: Conversation restore fidelity", () => {
  /**
   * **Validates: Requirements 6.5**
   *
   * For any Conversation stored in localStorage, restoring it produces a
   * chat state whose messages, history, and results fields are deeply equal
   * to the stored values.
   */
  it("round-trip through localStorage preserves messages, history, and results", () => {
    fc.assert(
      fc.property(conversationArb, (conversation) => {
        mockStorage.clear();
        writeConversations([conversation]);
        const restored = readConversations();

        expect(restored).toHaveLength(1);
        const r = restored[0];

        expect(r.messages).toEqual(conversation.messages);
        expect(r.history).toEqual(conversation.history);
        expect(r.results).toEqual(conversation.results);
      })
    );
  });

  it("round-trip preserves all fields of a Conversation", () => {
    fc.assert(
      fc.property(conversationArb, (conversation) => {
        mockStorage.clear();
        writeConversations([conversation]);
        const [restored] = readConversations();

        expect(restored.id).toBe(conversation.id);
        expect(restored.title).toBe(conversation.title);
        expect(restored.created_at).toBe(conversation.created_at);
        expect(restored.last_active_at).toBe(conversation.last_active_at);
        expect(restored.messages).toEqual(conversation.messages);
        expect(restored.history).toEqual(conversation.history);
        expect(restored.results).toEqual(conversation.results);
      })
    );
  });

  it("round-trip preserves multiple conversations", () => {
    fc.assert(
      fc.property(
        fc.array(conversationArb, { minLength: 1, maxLength: 15 }),
        (conversations) => {
          mockStorage.clear();

          // Deduplicate by ID — keep the last occurrence per ID (most recent write wins)
          const byId = new Map<string, Conversation>();
          for (const c of conversations) {
            byId.set(c.id, c);
          }
          const uniqueConversations = Array.from(byId.values());

          writeConversations(uniqueConversations);
          const stored = readConversations();

          // Every stored conversation must have its messages/history/results intact
          for (const storedConv of stored) {
            const original = uniqueConversations.find((c) => c.id === storedConv.id);
            expect(original).toBeDefined();
            if (original) {
              expect(storedConv.messages).toEqual(original.messages);
              expect(storedConv.history).toEqual(original.history);
              expect(storedConv.results).toEqual(original.results);
            }
          }
        }
      )
    );
  });
});