// SPDX-License-Identifier: BUSL-1.1
// Copyright (c) 2025 StellaOps

using Microsoft.Extensions.Options;
using StellaOps.Platform.WebService.Options;

namespace StellaOps.Platform.WebService.Services;

/// <summary>
/// Composes a final <see cref="PlatformEnvironmentSettingsOptions"/> from three layers:
/// <list type="number">
///   <item>Environment variables (via <see cref="Configuration.StellaOpsEnvVarPostConfigure"/>)</item>
///   <item>YAML/JSON configuration (standard IOptions binding)</item>
///   <item>Database (via <see cref="IEnvironmentSettingsStore"/>)</item>
/// </list>
/// Layer 3 (DB) has highest priority and is overlaid last.
/// </summary>
public sealed class EnvironmentSettingsComposer
{
    private readonly IOptionsMonitor<PlatformServiceOptions> _optionsMonitor;
    private readonly IEnvironmentSettingsStore _store;

    public EnvironmentSettingsComposer(
        IOptionsMonitor<PlatformServiceOptions> optionsMonitor,
        IEnvironmentSettingsStore store)
    {
        _optionsMonitor = optionsMonitor ?? throw new ArgumentNullException(nameof(optionsMonitor));
        _store = store ?? throw new ArgumentNullException(nameof(store));
    }

    /// <summary>
    /// Returns the merged environment settings with all three layers applied.
    /// </summary>
    public async Task<PlatformEnvironmentSettingsOptions> ComposeAsync(CancellationToken ct = default)
    {
        var source = _optionsMonitor.CurrentValue.EnvironmentSettings;

        // Clone the options so we don't mutate the originals
        var merged = new PlatformEnvironmentSettingsOptions
        {
            ClientId = source.ClientId,
            AuthorizeEndpoint = source.AuthorizeEndpoint,
            TokenEndpoint = source.TokenEndpoint,
            LogoutEndpoint = source.LogoutEndpoint,
            RedirectUri = source.RedirectUri,
            PostLogoutRedirectUri = source.PostLogoutRedirectUri,
            Scope = source.Scope,
            Audience = source.Audience,
            DpopAlgorithms = new List<string>(source.DpopAlgorithms),
            RefreshLeewaySeconds = source.RefreshLeewaySeconds,
            ApiBaseUrls = new Dictionary<string, string>(source.ApiBaseUrls, StringComparer.OrdinalIgnoreCase),
            OtlpEndpoint = source.OtlpEndpoint,
            TelemetrySampleRate = source.TelemetrySampleRate,
            WelcomeTitle = source.WelcomeTitle,
            WelcomeMessage = source.WelcomeMessage,
            WelcomeDocsUrl = source.WelcomeDocsUrl,
            DoctorFixEnabled = source.DoctorFixEnabled,
        };

        // Overlay DB values (Layer 3 — highest priority)
        var dbSettings = await _store.GetAllAsync(ct).ConfigureAwait(false);

        foreach (var (key, value) in dbSettings)
        {
            if (key.StartsWith("ApiBaseUrls:", StringComparison.OrdinalIgnoreCase))
            {
                var serviceName = key["ApiBaseUrls:".Length..];
                merged.ApiBaseUrls[serviceName] = value;
            }
            else
            {
                // Map scalar settings by key name
                ApplyScalarSetting(merged, key, value);
            }
        }

        return merged;
    }

    private static void ApplyScalarSetting(PlatformEnvironmentSettingsOptions options, string key, string value)
    {
        // Case-insensitive key matching for known scalar settings
        if (string.Equals(key, "ClientId", StringComparison.OrdinalIgnoreCase))
            options.ClientId = value;
        else if (string.Equals(key, "AuthorizeEndpoint", StringComparison.OrdinalIgnoreCase))
            options.AuthorizeEndpoint = value;
        else if (string.Equals(key, "TokenEndpoint", StringComparison.OrdinalIgnoreCase))
            options.TokenEndpoint = value;
        else if (string.Equals(key, "LogoutEndpoint", StringComparison.OrdinalIgnoreCase))
            options.LogoutEndpoint = value;
        else if (string.Equals(key, "RedirectUri", StringComparison.OrdinalIgnoreCase))
            options.RedirectUri = value;
        else if (string.Equals(key, "PostLogoutRedirectUri", StringComparison.OrdinalIgnoreCase))
            options.PostLogoutRedirectUri = value;
        else if (string.Equals(key, "Scope", StringComparison.OrdinalIgnoreCase))
            options.Scope = value;
        else if (string.Equals(key, "Audience", StringComparison.OrdinalIgnoreCase))
            options.Audience = value;
        else if (string.Equals(key, "OtlpEndpoint", StringComparison.OrdinalIgnoreCase))
            options.OtlpEndpoint = value;
        else if (string.Equals(key, "TelemetrySampleRate", StringComparison.OrdinalIgnoreCase)
                 && double.TryParse(value, out var rate))
            options.TelemetrySampleRate = rate;
        else if (string.Equals(key, "WelcomeTitle", StringComparison.OrdinalIgnoreCase))
            options.WelcomeTitle = value;
        else if (string.Equals(key, "WelcomeMessage", StringComparison.OrdinalIgnoreCase))
            options.WelcomeMessage = value;
        else if (string.Equals(key, "WelcomeDocsUrl", StringComparison.OrdinalIgnoreCase))
            options.WelcomeDocsUrl = value;
        else if (string.Equals(key, "DoctorFixEnabled", StringComparison.OrdinalIgnoreCase)
                 && bool.TryParse(value, out var fix))
            options.DoctorFixEnabled = fix;
    }
}