// Exercise 2: layered configuration like Microsoft.Extensions.Configuration (medium)
//
// ASP.NET Core merges configuration sources in order; later sources win.
// Keys are hierarchical and case-insensitive, joined with ":" — e.g.
// "ConnectionStrings:Default". Environment variables use "__" instead of ":"
// (ConnectionStrings__Default) because ":" isn't valid in env var names on
// every OS.
//
// Implement the LayeredConfig class:
//   - AddSource(IDictionary<string,string> values): adds a source on top
//   - AddEnvironment(IDictionary<string,string> env, string prefix):
//     only variables starting with `prefix` (e.g. "SHOP_") are included;
//     the prefix is stripped and "__" is translated to ":"
//   - this[string key]: returns the value from the LAST source that defines
//     the key (case-insensitive), or null
//   - GetSection(string prefix): returns a Dictionary of child key -> value for
//     every key starting with "prefix:", with the prefix removed, using the
//     same precedence rules
//
// Run with: dotnet run (inside a console project).

using System;
using System.Collections.Generic;

class LayeredConfig
{
    // TODO: fields

#pragma warning disable IDE0060
    public void AddSource(IDictionary<string, string> values)
    {
        // TODO
    }

    public void AddEnvironment(IDictionary<string, string> env, string prefix)
    {
        // TODO
    }

    public string? this[string key] => null; // TODO

    public Dictionary<string, string> GetSection(string prefix)
    {
        // TODO
        return new Dictionary<string, string>();
    }
#pragma warning restore IDE0060
}

class Program
{
    static void Main()
    {
        int pass = 0, total = 0;

        var appsettings = new Dictionary<string, string>
        {
            ["Logging:Level"] = "Information",
            ["ConnectionStrings:Default"] = "Server=localhost",
            ["ConnectionStrings:Reports"] = "Server=reports",
        };
        var appsettingsProd = new Dictionary<string, string>
        {
            ["Logging:Level"] = "Warning",
        };
        var env = new Dictionary<string, string>
        {
            ["SHOP_ConnectionStrings__Default"] = "Server=prod-db",
            ["PATH"] = "/usr/bin",
        };

        var config = new LayeredConfig();
        config.AddSource(appsettings);
        config.AddSource(appsettingsProd);
        config.AddEnvironment(env, "SHOP_");

        total++;
        if (config["Logging:Level"] == "Warning") { Console.WriteLine("PASS: later file overrides earlier"); pass++; }
        else Console.WriteLine("FAIL: Logging:Level = " + config["Logging:Level"]);

        total++;
        if (config["connectionstrings:default"] == "Server=prod-db") { Console.WriteLine("PASS: env var overrides, case-insensitive"); pass++; }
        else Console.WriteLine("FAIL: ConnectionStrings:Default = " + config["connectionstrings:default"]);

        total++;
        if (config["PATH"] == null) { Console.WriteLine("PASS: unprefixed env vars ignored"); pass++; }
        else Console.WriteLine("FAIL: PATH leaked into config");

        var section = config.GetSection("ConnectionStrings");
        total++;
        if (section.Count == 2 && section["Default"] == "Server=prod-db" && section["Reports"] == "Server=reports")
        { Console.WriteLine("PASS: GetSection"); pass++; }
        else Console.WriteLine("FAIL: GetSection " + string.Join(", ", section));

        Console.WriteLine($"--- {pass}/{total} checks passed ---");
    }
}