ccn/Packages/Localization/Tests/Cases/Public/Methods/NegotiateTests.swift

import Foundation
import Testing

@testable import Localization

@Suite(
    "Negotiate method",
    .tags(.method)
)
struct NegotiateTests {

    // MARK: Constants

    private let negotiate = Negotiate(bundle: .module)

    // MARK: Functional tests

    @Test
    func `matches an exact language tag`() {
        let language = negotiate(acceptLanguage: "de")

        #expect(language == "de")
    }

    @Test
    func `matches a regional language tag`() {
        let language = negotiate(acceptLanguage: "de-AT")

        #expect(language == "de")
    }

    @Test
    func `matches a regional catalog language exactly`() {
        let language = negotiate(acceptLanguage: "pt-BR")

        #expect(language == "pt-BR")
    }

    @Test
    func `matches a regional catalog language by its primary subtag`() {
        let language = negotiate(acceptLanguage: "pt")

        #expect(language == "pt-BR")
    }

    @Test
    func `respects the header order of preference`() {
        let language = negotiate(acceptLanguage: "de, en")

        #expect(language == "de")
    }

    @Test
    func `orders the language tags by descending quality weight`() {
        let language = negotiate(acceptLanguage: "en;q=0.5, de;q=0.9")

        #expect(language == "de")
    }

    @Test
    func `treats a tag without a weight as the highest preference`() {
        let language = negotiate(acceptLanguage: "en;q=0.9, de")

        #expect(language == "de")
    }

    @Test
    func `treats a tag with a malformed weight as the highest preference`() {
        let language = negotiate(acceptLanguage: "en;q=0.9, de;q=broken")

        #expect(language == "de")
    }

    @Test
    func `drops language tags weighted as not acceptable`() {
        let language = negotiate(acceptLanguage: "de;q=0, en;q=0.8")

        #expect(language == "en")
    }

    @Test
    func `falls back to the default when every tag is weighted as not acceptable`() {
        let language = negotiate(acceptLanguage: "de;q=0, fr;q=0")

        #expect(language == "en")
    }

    @Test
    func `serves the default language for a wildcard`() {
        let language = negotiate(acceptLanguage: "fr;q=0.9, *;q=0.5")

        #expect(language == "en")
    }

    @Test
    func `trims whitespace around the language tags`() {
        let language = negotiate(acceptLanguage: " de , en ")

        #expect(language == "de")
    }

    @Test
    func `falls back to the default for an unsupported language`() {
        let language = negotiate(acceptLanguage: "fr")

        #expect(language == "en")
    }

    @Test
    func `falls back to the default for a missing header`() {
        let language = negotiate(acceptLanguage: nil)

        #expect(language == "en")
    }

    @Test
    func `falls back to the default for an empty header`() {
        let language = negotiate(acceptLanguage: "")

        #expect(language == "en")
    }

    @Test
    func `falls back to the default for a header without language tags`() {
        let language = negotiate(acceptLanguage: " , ;q=0.5,")

        #expect(language == "en")
    }

    @Test
    func `honours a supported requested language over the header`() {
        let language = negotiate(
            requested: "de",
            acceptLanguage: "en"
        )

        #expect(language == "de")
    }

    @Test
    func `matches a regional requested language by its primary subtag`() {
        let language = negotiate(
            requested: "de-AT",
            acceptLanguage: "en"
        )

        #expect(language == "de")
    }

    @Test
    func `ignores an unsupported requested language`() {
        let language = negotiate(
            requested: "fr",
            acceptLanguage: "de"
        )

        #expect(language == "de")
    }

    @Test
    func `ignores an empty requested language`() {
        let language = negotiate(
            requested: "",
            acceptLanguage: "de"
        )

        #expect(language == "de")
    }

}