//
// Copyright Amazon.com Inc. or its affiliates.
// All Rights Reserved.
//
// SPDX-License-Identifier: Apache-2.0
//

import XCTest
@testable import AWSPredictionsPlugin

final class EventStreamCoderTestCase: XCTestCase {
    struct Model: Codable, Equatable {
        let foo: Int
        let bar: String
        let baz: Baz

        struct Baz: Codable, Equatable {
            let quux: Bool
        }
    }

    /// Given: A payload and headers.
    /// When: Encoding the payload and headers using `EventStream.Encoder().encode(payload:headers:)`
    /// Then: The returned data should be conformant to the EventStream spec.
    func testBasicModelWithStringHeader() throws {
        let model = Model(foo: 42, bar: "hello, world!", baz: .init(quux: true))

        let headers: [String: EventStream.HeaderValue] = [
            "string_ex": .string("abc")
        ]

        let data = try JSONEncoder().encode(model)
        let encoded = EventStream.Encoder().encode(payload: data, headers: headers)
        let encodedBytes = [UInt8](encoded)

        let expectedBytes: [UInt8] = [
            // Total Byte Length
            // 84 bytes
            [0, 0, 0, 84],

            // Headers Byte Length
            // 16 bytes
            [0, 0, 0, 16],

            // Prelude CRC
            [181, 6, 166, 6],

            // Headers
            // Headers - Header Name Byte Length
            [9],
            // Headers - Header Name
            // "string_ex"
            [115, 116, 114, 105, 110, 103, 95, 101, 120],
            // Headers - Header Value Type
            // 7 == String
            [7],
            // Headers - Value String Byte Length
            // 3 bytes
            [0, 3],
            // Headers - Value String
            // "abc"
            [97, 98, 99],

            // Payload
            [UInt8](data),
        ].flatMap { $0 }

        XCTAssertEqual(encodedBytes.dropLast(4), expectedBytes)
    }


    /// Given: A payload and headers
    /// When: Encoding the payload and headers to data, then decoding that data.
    /// Then: The payload and headers of the decoded data should equal that of the payload
    /// and headers before they were initially encoded.
    func testEncodingThenDecoding() throws {
        let model = Model(foo: 42, bar: "hello, world!", baz: .init(quux: true))

        let _header = (key: "string_ex", value: "abc")
        let headers: [String: EventStream.HeaderValue] = [
            _header.key: .string(_header.value)
        ]

        let data = try JSONEncoder().encode(model)
        let encoded = EventStream.Encoder().encode(payload: data, headers: headers)

        let decoded = try EventStream.Decoder().decode(data: encoded)
        let decodedModel = try JSONDecoder().decode(Model.self, from: decoded.payload)
        XCTAssertEqual(model, decodedModel)

        let decodedHeader = try XCTUnwrap(decoded.headers.first)
        XCTAssertEqual(decodedHeader.name, _header.key)
        XCTAssertEqual(decodedHeader.value, _header.value)
    }
}