using AcDream.App.Configuration;

namespace AcDream.App.Tests.Configuration;

/// <summary>
/// Campaign LA slice LA1 review fix (F5): pins
/// <see cref="SessionConfigArgumentParsing"/>'s trailing-flag edge case —
/// <c>--session-config</c> present as the LAST argument with nothing after
/// it must be distinguishable from the flag being entirely absent, so
/// <c>Program.cs</c> can turn it into a hard error instead of a silent
/// fall-through to the env-var/positional dat-dir path.
/// </summary>
public sealed class SessionConfigArgumentParsingTests
{
    private const string Flag = "--session-config";

    [Fact]
    public void FlagWithAFollowingValueReturnsThatValueAndIsPresent()
    {
        string? value = SessionConfigArgumentParsing.ExtractFlagValue(
            ["D:\\dats", Flag, "session.json"],
            Flag,
            out bool present);

        Assert.True(present);
        Assert.Equal("session.json", value);
    }

    [Fact]
    public void FlagAbsentReturnsNullAndIsNotPresent()
    {
        string? value = SessionConfigArgumentParsing.ExtractFlagValue(
            ["D:\\dats"],
            Flag,
            out bool present);

        Assert.False(present);
        Assert.Null(value);
    }

    [Fact]
    public void TrailingFlagWithNoValueIsPresentWithANullValue()
    {
        string? value = SessionConfigArgumentParsing.ExtractFlagValue(
            ["D:\\dats", Flag],
            Flag,
            out bool present);

        // This is the case Program.cs must turn into exit code 2 — present
        // but no value is categorically different from "not present at
        // all", even though both currently yield a null return value.
        Assert.True(present);
        Assert.Null(value);
    }

    [Fact]
    public void FlagAloneAsTheOnlyArgumentIsPresentWithANullValue()
    {
        string? value = SessionConfigArgumentParsing.ExtractFlagValue(
            [Flag],
            Flag,
            out bool present);

        Assert.True(present);
        Assert.Null(value);
    }

    [Fact]
    public void WithoutFlagAndValueDropsTheFlagAndItsValue()
    {
        string[] positional = SessionConfigArgumentParsing.WithoutFlagAndValue(
            ["D:\\dats", Flag, "session.json", "extra"],
            Flag);

        Assert.Equal(["D:\\dats", "extra"], positional);
    }

    [Fact]
    public void WithoutFlagAndValueTrailingFlagDropsOnlyTheFlagItself()
    {
        string[] positional = SessionConfigArgumentParsing.WithoutFlagAndValue(
            ["D:\\dats", Flag],
            Flag);

        Assert.Equal(["D:\\dats"], positional);
    }

    [Fact]
    public void WithoutFlagAndValueLeavesArgumentsUnchangedWhenFlagIsAbsent()
    {
        string[] positional = SessionConfigArgumentParsing.WithoutFlagAndValue(
            ["D:\\dats"],
            Flag);

        Assert.Equal(["D:\\dats"], positional);
    }
}