import XCTest
@testable import AIStudyApp

final class MarkedReadStoreTests: XCTestCase {

    private let store = MarkedReadStore.shared
    private let defaults = UserDefaults.standard
    private let key = "zx_marked_read_material_ids"

    override func setUp() {
        super.setUp()
        // Clean up persisted state before each test
        defaults.removeObject(forKey: key)
    }

    override func tearDown() {
        defaults.removeObject(forKey: key)
        super.tearDown()
    }

    // MARK: - contains

    func test_contains_returnsFalse_for_unmarkedId() {
        XCTAssertFalse(store.contains("mat-unknown"))
    }

    func test_contains_returnsTrue_after_mark() {
        store.mark("mat-001")
        XCTAssertTrue(store.contains("mat-001"))
    }

    func test_contains_returnsFalse_after_unmark() {
        store.mark("mat-001")
        store.unmark("mat-001")
        XCTAssertFalse(store.contains("mat-001"))
    }

    // MARK: - mark

    func test_mark_persists_to_userDefaults() {
        store.mark("mat-persist")
        let arr = defaults.stringArray(forKey: key) ?? []
        XCTAssertTrue(arr.contains("mat-persist"))
    }

    func test_mark_is_idempotent() {
        store.mark("mat-001")
        store.mark("mat-001")
        store.mark("mat-001")
        let arr = defaults.stringArray(forKey: key) ?? []
        // Set semantics: no duplicates
        XCTAssertEqual(arr.count, 1)
    }

    func test_mark_multiple_ids() {
        store.mark("mat-a")
        store.mark("mat-b")
        store.mark("mat-c")
        let arr = defaults.stringArray(forKey: key) ?? []
        XCTAssertEqual(arr.count, 3)
        XCTAssertTrue(arr.contains("mat-a"))
        XCTAssertTrue(arr.contains("mat-b"))
        XCTAssertTrue(arr.contains("mat-c"))
    }

    // MARK: - unmark

    func test_unmark_removes_from_persisted_array() {
        store.mark("mat-a")
        store.mark("mat-b")
        store.unmark("mat-a")
        let arr = defaults.stringArray(forKey: key) ?? []
        XCTAssertFalse(arr.contains("mat-a"))
        XCTAssertTrue(arr.contains("mat-b"))
    }

    func test_unmark_nonexistent_is_safe() {
        store.unmark("mat-nope")
        // Should not crash or corrupt state
        let arr = defaults.stringArray(forKey: key) ?? []
        XCTAssertEqual(arr.count, 0)
    }

    // MARK: - Persistence across instances

    func test_state_survives_reinit() {
        store.mark("mat-survive")

        // Simulate app restart by creating a new instance (singleton in real app,
        // but we can verify the persisted data is loadable)
        let newStore = MarkedReadStore.shared
        // Singleton — same instance. But the key test is: data survived UserDefaults write.
        XCTAssertTrue(newStore.contains("mat-survive"))
    }

    // MARK: - Empty string edge cases

    func test_empty_string_as_id() {
        store.mark("")
        XCTAssertTrue(store.contains(""))
        store.unmark("")
        XCTAssertFalse(store.contains(""))
    }
}