using Gateway.Models;
using Microsoft.Extensions.Options;

namespace Gateway.Services;

/// <summary>
/// Normalizes provider-specific campaign statuses into platform-standard statuses.
/// 
/// Each advertising channel (Google Ads, Meta, TikTok, etc.) reports campaign state
/// using its own vocabulary. This service translates those into the platform's
/// unified status set: draft, staged, pending, active, paused, completed, cancelled, error.
///
/// Mapping priority:
///   1. Channel-specific mapping from config (e.g. google_ads → ENABLED → active)
///   2. Common/internal mappings (e.g. submitted → active, pending_review → pending)
///   3. Pass-through if the raw status is already a valid platform status
///   4. "error" fallback with a warning log for truly unknown statuses
/// </summary>
public sealed class ProviderStatusNormalizer
{
    private readonly MultiChannelConfig _config;
    private readonly ILogger<ProviderStatusNormalizer> _log;

    /// <summary>The canonical set of platform-level statuses.</summary>
    private static readonly HashSet<string> PlatformStatuses = new(StringComparer.OrdinalIgnoreCase)
    {
        "draft", "staged", "pending", "active", "paused", "completed", "cancelled", "error"
    };

    /// <summary>
    /// Internal/transitional statuses used during launch orchestration.
    /// These are not provider-specific but arise from the platform's own workflow.
    /// </summary>
    private static readonly Dictionary<string, string> CommonMappings = new(StringComparer.OrdinalIgnoreCase)
    {
        // Launch service assigns these during dispatch
        ["submitted"]      = "active",
        ["pending_review"]  = "pending",
        ["stub_provider"]   = "pending",

        // Webhook / callback transitional states
        ["approved"]        = "active",
        ["rejected"]        = "error",
        ["suspended"]       = "paused",
        ["budget_depleted"] = "paused",
        ["expired"]         = "completed",
        ["archived"]        = "completed",
        ["deleted"]         = "cancelled",
        ["in_process"]      = "pending",
        ["in_review"]       = "pending",
        ["learning"]        = "active",      // Meta "learning phase"
        ["limited"]         = "active",      // Google "limited by budget" etc.
    };

    public ProviderStatusNormalizer(
        IOptions<MultiChannelConfig> config,
        ILogger<ProviderStatusNormalizer> log)
    {
        _config = config.Value;
        _log = log;
    }

    /// <summary>
    /// Normalize a raw provider status into a platform status.
    /// </summary>
    /// <param name="channelType">Channel identifier (e.g. "google_ads", "meta", "tiktok").</param>
    /// <param name="rawProviderStatus">The status string as returned by the provider.</param>
    /// <returns>A valid platform status string.</returns>
    public string Normalize(string? channelType, string? rawProviderStatus)
    {
        if (string.IsNullOrWhiteSpace(rawProviderStatus))
            return "error";

        var raw = rawProviderStatus.Trim();

        // 1. Try channel-specific mapping from config
        if (!string.IsNullOrWhiteSpace(channelType))
        {
            var provider = _config.GetChannel(channelType);
            if (provider?.StatusMappings != null &&
                provider.StatusMappings.TryGetValue(raw, out var mapped))
            {
                _log.LogDebug("[StatusNorm] {Channel}/{RawStatus} → {PlatformStatus} (config)",
                    channelType, raw, mapped);
                return mapped;
            }
        }

        // 2. Try common/internal mappings
        if (CommonMappings.TryGetValue(raw, out var common))
        {
            _log.LogDebug("[StatusNorm] {RawStatus} → {PlatformStatus} (common)",
                raw, common);
            return common;
        }

        // 3. If the raw value is already a valid platform status, pass through
        if (PlatformStatuses.Contains(raw))
        {
            _log.LogDebug("[StatusNorm] {RawStatus} → pass-through (already platform status)", raw);
            return raw.ToLowerInvariant();
        }

        // 4. Unknown — log warning and return "error"
        _log.LogWarning(
            "[StatusNorm] Unknown provider status: channel={Channel}, raw={RawStatus}. Defaulting to 'error'. " +
            "Add a mapping in MultiChannel.Channels[].StatusMappings or CommonMappings.",
            channelType ?? "(none)", raw);

        return "error";
    }

    /// <summary>
    /// Resolve the platform status for a sync operation.
    /// If an explicit platform status is provided, validate and use it.
    /// Otherwise, normalize the provider status.
    /// </summary>
    /// <param name="channelType">Channel identifier.</param>
    /// <param name="explicitStatus">Explicitly provided platform status (optional).</param>
    /// <param name="rawProviderStatus">Raw provider status (optional).</param>
    /// <returns>A valid platform status string.</returns>
    public string Resolve(string? channelType, string? explicitStatus, string? rawProviderStatus)
    {
        // If an explicit platform status was given, validate it
        if (!string.IsNullOrWhiteSpace(explicitStatus))
        {
            if (PlatformStatuses.Contains(explicitStatus))
                return explicitStatus.ToLowerInvariant();

            _log.LogWarning("[StatusNorm] Invalid explicit status '{Status}', normalizing as provider status instead.",
                explicitStatus);
            // Fall through to normalization
        }

        return Normalize(channelType, rawProviderStatus);
    }

    /// <summary>
    /// Get all configured mappings for a channel (for diagnostics / admin display).
    /// </summary>
    public Dictionary<string, string> GetMappings(string channelType)
    {
        var result = new Dictionary<string, string>(CommonMappings, StringComparer.OrdinalIgnoreCase);

        var provider = _config.GetChannel(channelType);
        if (provider?.StatusMappings != null)
        {
            foreach (var kv in provider.StatusMappings)
                result[kv.Key] = kv.Value; // Channel-specific overrides common
        }

        return result;
    }

    /// <summary>
    /// Check whether a string is a valid platform status.
    /// </summary>
    public static bool IsValidPlatformStatus(string? status) =>
        !string.IsNullOrWhiteSpace(status) && PlatformStatuses.Contains(status);
}