using System.Text.Json;
using PrintService.Models;

namespace PrintService.Services;

/// <summary>
/// Loads printer-config.json (global and local), merging local over global.
/// Mirrors the same logic used in PrintServiceTray.
/// </summary>
public class ConfigurationService
{
    private readonly string _globalConfigPath;
    private readonly string _localConfigPath;
    private readonly ILogger<ConfigurationService> _logger;

    public ConfigurationService(ILogger<ConfigurationService> logger)
    {
        _logger = logger;

        _globalConfigPath = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData),
            "LAAPC", "printer-config.json");

        _localConfigPath = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
            "LAAPC", "printer-config.json");
    }

    /// <summary>
    /// Load merged configuration. Returns an empty config (not null) if no files exist.
    /// </summary>
    public PrinterConfiguration Load()
    {
        var config = new PrinterConfiguration();

        if (File.Exists(_globalConfigPath))
        {
            try
            {
                var json = File.ReadAllText(_globalConfigPath);
                var global = JsonSerializer.Deserialize<PrinterConfiguration>(json);
                if (global != null)
                    config = global;
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Failed to read global printer config from {Path}", _globalConfigPath);
            }
        }

        if (File.Exists(_localConfigPath))
        {
            try
            {
                var json = File.ReadAllText(_localConfigPath);
                var local = JsonSerializer.Deserialize<PrinterConfiguration>(json);
                if (local != null)
                {
                    // Local overrides global per document type
                    foreach (var kvp in local.DocumentTypes)
                        config.DocumentTypes[kvp.Key] = kvp.Value;
                }
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Failed to read local printer config from {Path}", _localConfigPath);
            }
        }

        if (config.DocumentTypes.Count == 0)
            _logger.LogWarning("No document types found in printer-config.json. Checked: {Global} and {Local}",
                _globalConfigPath, _localConfigPath);

        return config;
    }

    /// <summary>
    /// Get a single document type config by name (case-insensitive).
    /// </summary>
    public DocumentTypeConfig? GetDocumentType(string documentType)
    {
        var config = Load();
        return config.DocumentTypes
            .FirstOrDefault(kvp => kvp.Key.Equals(documentType, StringComparison.OrdinalIgnoreCase))
            .Value;
    }
}