import XCTest
import ForgeColor
@testable import ForgeGrade

final class SerializationTests: XCTestCase {

    func makeStack() -> GradeStack {
        var set = CurveSet.identity
        set.master = Curve(points: [.init(x: 0, y: 0.05), .init(x: 1, y: 0.95)])
        return GradeStack(nodes: [
            GradeNode(kind: .inputTransform(.arriLogC4AWG4)),
            GradeNode(kind: .cdl(CDL(
                slope: SIMD3(1.1, 0.95, 1.02),
                offset: SIMD3(0.01, -0.005, 0),
                power: SIMD3(0.98, 1.03, 1.0),
                saturation: 1.15))),
            GradeNode(kind: .curves(set)),
            GradeNode(kind: .saturation(0.9), isEnabled: false),
            GradeNode(kind: .lut3d(Lut3D.build(size: 2) { $0 * 0.9 })),
            GradeNode(kind: .outputTransform(.rec709Display)),
        ])
    }

    // Round trip: encode -> decode -> same stack (ids, kinds, params, enabled flags).
    func testRoundTrip() throws {
        let stack = makeStack()
        let data = try GradeSnapshot.encode(stack)
        let back = try GradeSnapshot.decode(data)
        XCTAssertEqual(back.nodes.count, stack.nodes.count)
        for (a, b) in zip(stack.nodes, back.nodes) {
            XCTAssertEqual(a.id, b.id)
            XCTAssertEqual(a.isEnabled, b.isEnabled)
        }
        // Behavioral equality: same eval on sample pixels.
        for px in [SIMD3<Float>(0.2, 0.4, 0.6), SIMD3(0.8, 0.1, 0.5)] {
            let ea = stack.evaluate(px)
            let eb = back.evaluate(px)
            XCTAssertEqual(ea.x, eb.x, accuracy: 1e-6)
            XCTAssertEqual(ea.y, eb.y, accuracy: 1e-6)
            XCTAssertEqual(ea.z, eb.z, accuracy: 1e-6)
        }
    }

    // Deterministic: re-encoding a decoded stack is byte-identical.
    func testDeterministicEncoding() throws {
        let stack = makeStack()
        let data1 = try GradeSnapshot.encode(stack)
        let back = try GradeSnapshot.decode(data1)
        let data2 = try GradeSnapshot.encode(back)
        XCTAssertEqual(data1, data2)
    }

    // Unknown node kind fails loudly, not silently dropped.
    func testUnknownNodeKindFails() {
        let json = """
        {"nodes":[{"id":"6EC0BD7F-11C0-43DA-975E-2A8AD9EBAE0B","isEnabled":true,"kind":{"type":"warpDrive"}}],"version":1}
        """
        XCTAssertThrowsError(try GradeSnapshot.decode(Data(json.utf8)))
    }

    // Version field present; future-proofing.
    func testVersionField() throws {
        let data = try GradeSnapshot.encode(GradeStack(nodes: []))
        let obj = try JSONSerialization.jsonObject(with: data) as? [String: Any]
        XCTAssertEqual(obj?["version"] as? Int, 1)
    }

    // Wrong version rejected.
    func testWrongVersionRejected() {
        let json = #"{"nodes":[],"version":99}"#
        XCTAssertThrowsError(try GradeSnapshot.decode(Data(json.utf8)))
    }
}