using System.Text;

namespace Books.Api.AiBookkeeper;

/// <summary>
/// Converts ChartOfAccountsDto to .toon format for AI Bookkeeper.
/// The .toon format is a structured text format with meta and accounts sections.
/// </summary>
public static class ToonFormatConverter
{
    /// <summary>
    /// Convert a chart of accounts to .toon format string.
    /// </summary>
    public static string ConvertToToon(ChartOfAccountsDto chartOfAccounts)
    {
        var sb = new StringBuilder();

        // Header comment
        sb.AppendLine("# Chart of Accounts for AI Bookkeeper");
        sb.AppendLine();

        // Meta section
        sb.AppendLine("meta:");
        sb.AppendLine("  source: Books API");
        sb.AppendLine($"  organizationId: {chartOfAccounts.CompanyId}");
        sb.AppendLine("  accountType: expense");
        sb.AppendLine($"  totalAccounts: {chartOfAccounts.Accounts.Count}");
        sb.AppendLine();

        // Accounts section
        // Format: number,name,category,vatCode,region,vatRubric,suggestions
        sb.AppendLine($"accounts[{chartOfAccounts.Accounts.Count}]{{number,name,category,vatCode,region,vatRubric,suggestions}}:");

        foreach (var account in chartOfAccounts.Accounts)
        {
            var vatCode = MapVatCode(account.VatCodeId);
            var region = DetermineRegion(account.VatCodeId);
            var category = MapCategory(account.AccountType);
            var suggestions = GenerateSuggestions(account.Name, account.AccountNumber);

            // Format: number,name,category,vatCode,region,vatRubric,suggestions
            sb.AppendLine($"  {account.AccountNumber},{EscapeCommas(account.Name)},{category},{vatCode},{region},,{suggestions}");
        }

        return sb.ToString();
    }

    public static string MapVatCode(string? vatCodeId)
    {
        if (string.IsNullOrEmpty(vatCodeId))
            return "";

        return vatCodeId.ToUpperInvariant() switch
        {
            "I25" => "I25",
            "U25" => "",  // Output VAT not relevant for expense accounts
            "INGEN" => "",
            _ => vatCodeId
        };
    }

    public static string DetermineRegion(string? vatCodeId)
    {
        if (string.IsNullOrEmpty(vatCodeId))
            return "";

        return vatCodeId.ToUpperInvariant() switch
        {
            "IEUV" => "EU",      // EU goods
            "IEUY" => "EU",      // EU services
            "IVV" => "WORLD",    // World goods
            "IVY" => "WORLD",    // World services
            _ => ""              // Empty = available for all regions
        };
    }

    public static string MapCategory(string accountType)
    {
        return accountType switch
        {
            "expense" => "Administrationsomkostninger",
            "cogs" => "Variable omkostninger",
            "personnel" => "Lønomkostninger",
            "financial" => "Renteudgifter",
            _ => "Øvrige omkostninger"
        };
    }

    public static string GenerateSuggestions(string name, string accountNumber)
    {
        // Generate search keywords from account name
        var suggestions = new List<string>();

        // Add words from name (lowercase, no special chars)
        var words = name.ToLowerInvariant()
            .Replace(",", " ")
            .Replace(".", " ")
            .Replace("-", " ")
            .Split(' ', StringSplitOptions.RemoveEmptyEntries)
            .Where(w => w.Length > 2);

        suggestions.AddRange(words);

        // Add account number as suggestion
        suggestions.Add(accountNumber);

        return string.Join("|", suggestions.Distinct());
    }

    private static string EscapeCommas(string value)
    {
        // The .toon format uses commas as delimiters, so we need to handle commas in values
        return value.Replace(",", " ");
    }
}