using System.Text.Json;

namespace ApiRegistrationTool;

/// <summary>
/// Builds the Module → gateway short-code prefix map by reading
/// GB5Build/GB5Build/appsettings.json (ReverseProxy:Routes) at runtime.
///
/// Route entries look like:
///   "Accounts-route": { "Match": { "Path": "/as/{**catch-all}" }, ... }
///
/// Module name  = route key with the "-route" suffix stripped.
/// Prefix       = first path segment of Match.Path.
///
/// Adding support for a new module is just adding its route to the gateway's
/// appsettings.json — nothing here needs to change.
/// </summary>
public sealed class ModulePrefixResolver
{
    private readonly Dictionary<string, string> _map;

    private ModulePrefixResolver(Dictionary<string, string> map) => _map = map;

    public static ModulePrefixResolver Load(string gatewayAppSettingsPath)
    {
        var map = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

        if (!File.Exists(gatewayAppSettingsPath))
        {
            Console.ForegroundColor = ConsoleColor.Yellow;
            Console.WriteLine($"  [WARN] Gateway appsettings not found at {gatewayAppSettingsPath} — " +
                               "module prefixes will fall back to lowercased module names.");
            Console.ResetColor();
            return new ModulePrefixResolver(map);
        }

        using var stream = File.OpenRead(gatewayAppSettingsPath);
        using var doc    = JsonDocument.Parse(stream);

        if (!doc.RootElement.TryGetProperty("ReverseProxy", out var reverseProxy) ||
            !reverseProxy.TryGetProperty("Routes", out var routes))
        {
            return new ModulePrefixResolver(map);
        }

        foreach (var route in routes.EnumerateObject())
        {
            string key = route.Name;
            if (!key.EndsWith("-route", StringComparison.OrdinalIgnoreCase)) continue;
            string module = key[..^"-route".Length];

            if (!route.Value.TryGetProperty("Match", out var match) ||
                !match.TryGetProperty("Path", out var pathProp)) continue;

            string? path = pathProp.GetString();
            if (string.IsNullOrWhiteSpace(path)) continue;

            string prefix = "/" + path.TrimStart('/').Split('/', 2)[0];
            if (prefix.Length <= 1) continue;

            map[module] = prefix;
        }

        return new ModulePrefixResolver(map);
    }

    /// <summary>Returns the gateway prefix for a module, or a lowercased fallback if unmapped.</summary>
    public string GetPrefix(string module)
    {
        if (_map.TryGetValue(module, out var prefix)) return prefix;

        Console.ForegroundColor = ConsoleColor.Yellow;
        Console.WriteLine($"  [WARN] No gateway route found for module '{module}' — " +
                           $"add a \"{module}-route\" entry to GB5Build/appsettings.json. " +
                           $"Falling back to '/{module.ToLowerInvariant()}'.");
        Console.ResetColor();
        return "/" + module.ToLowerInvariant();
    }
}