using System.Text;

namespace CareFix.Api.Infrastructure;

/// <summary>Small RFC 4180 CSV reader (quoted fields, embedded commas, quotes and new lines).</summary>
public static class Csv
{
    public static List<Dictionary<string, string>> Read(string text)
    {
        var rows = ParseRows(text);
        if (rows.Count == 0) return [];
        var header = rows[0].Select(h => h.Trim().TrimStart('\uFEFF')).ToList();
        var result = new List<Dictionary<string, string>>();
        foreach (var r in rows.Skip(1))
        {
            if (r.All(string.IsNullOrWhiteSpace)) continue;
            var d = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            for (var i = 0; i < header.Count; i++) d[header[i]] = i < r.Count ? r[i].Trim() : "";
            result.Add(d);
        }
        return result;
    }

    private static List<List<string>> ParseRows(string text)
    {
        var rows = new List<List<string>>();
        var row = new List<string>();
        var field = new StringBuilder();
        var inQuotes = false;
        for (var i = 0; i < text.Length; i++)
        {
            var c = text[i];
            if (inQuotes)
            {
                if (c == '"' && i + 1 < text.Length && text[i + 1] == '"') { field.Append('"'); i++; }
                else if (c == '"') inQuotes = false;
                else field.Append(c);
                continue;
            }
            switch (c)
            {
                case '"': inQuotes = true; break;
                case ',': row.Add(field.ToString()); field.Clear(); break;
                case '\r': break;
                case '\n': row.Add(field.ToString()); field.Clear(); rows.Add(row); row = []; break;
                default: field.Append(c); break;
            }
        }
        if (field.Length > 0 || row.Count > 0) { row.Add(field.ToString()); rows.Add(row); }
        return rows;
    }

    public static bool Bool(string? v, bool fallback = false) =>
        string.IsNullOrWhiteSpace(v) ? fallback : v.Trim().ToLowerInvariant() is "1" or "y" or "yes" or "true";

    public static string? NullIfEmpty(string? v) => string.IsNullOrWhiteSpace(v) ? null : v.Trim();
}