using Disco.Plugins.ServiceTracker.Models;
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Text;

namespace Disco.Plugins.ServiceTracker.Services
{
    public class GoogleSheetService
    {
        private readonly GoogleSheetConfig _config;
        private readonly string _cachePath;

        public GoogleSheetService(GoogleSheetConfig config, string dataDirectory)
        {
            _config = config;
            _cachePath = Path.Combine(dataDirectory, "sheet_cache.csv");
        }

        public GoogleSheetResult FetchTickets()
        {
            var result = new GoogleSheetResult();
            if (!_config.Enabled || string.IsNullOrEmpty(_config.SpreadsheetId))
            {
                result.Error = "Google Sheet integration is disabled.";
                return result;
            }

            string csvData = null;
            if (File.Exists(_cachePath))
            {
                var cacheAge = DateTime.Now - File.GetLastWriteTime(_cachePath);
                if (cacheAge.TotalMinutes < _config.RefreshMinutes)
                    csvData = File.ReadAllText(_cachePath);
            }

            if (csvData == null)
            {
                try
                {
                    string url;
                    var id = _config.SpreadsheetId.Trim();
                    if (id.StartsWith("2PACX", StringComparison.OrdinalIgnoreCase))
                        url = "https://docs.google.com/spreadsheets/d/e/" + id + "/pub?output=csv&gid=" + _config.GId;
                    else
                        url = "https://docs.google.com/spreadsheets/d/" + id + "/export?format=csv&gid=" + _config.GId;
                    using (var client = new WebClient())
                    {
                        client.Encoding = Encoding.UTF8;
                        client.Headers.Add("User-Agent", "Mozilla/5.0 DiscoServiceTracker/1.0");
                        csvData = client.DownloadString(url);
                    }
                    if (csvData != null && csvData.TrimStart().StartsWith("<!DOCTYPE", StringComparison.OrdinalIgnoreCase))
                    {
                        if (File.Exists(_cachePath)) { csvData = File.ReadAllText(_cachePath); result.Warning = "Got HTML not CSV. Using cache."; }
                        else { result.Error = "Google returned HTML not CSV. Publish as CSV."; return result; }
                    }
                    else File.WriteAllText(_cachePath, csvData);
                }
                catch (WebException ex)
                {
                    if (File.Exists(_cachePath)) { csvData = File.ReadAllText(_cachePath); result.Warning = "Using cache. " + ex.Message; }
                    else { result.Error = "Fetch failed: " + ex.Message; return result; }
                }
                catch (Exception ex) { result.Error = "Error: " + ex.Message; return result; }
            }

            try
            {
                result.Tickets = ParseCsv(csvData);
                if (result.Tickets.Count == 0 && string.IsNullOrEmpty(result.Warning))
                    result.Warning = "Sheet OK but no open tickets found.";
            }
            catch (Exception ex) { result.Error = "Parse error: " + ex.Message; }
            return result;
        }

        private List<ExternalTicket> ParseCsv(string csvData)
        {
            var tickets = new List<ExternalTicket>();
            var lines = csvData.Split(new[] { '\n' }, StringSplitOptions.RemoveEmptyEntries);
            var usedIds = new HashSet<int>();

            for (int i = _config.HeaderRows; i < lines.Length; i++)
            {
                var fields = ParseCsvLine(lines[i]);
                if (fields.Count == 0) continue;
                bool allEmpty = true;
                for (int j = 0; j < fields.Count; j++) if (!string.IsNullOrWhiteSpace(fields[j])) { allEmpty = false; break; }
                if (allEmpty) continue;

                var rawTimestamp = RawGet(fields, _config.ColTimestamp);
                var rawEmail = RawGet(fields, _config.ColEmail);
                var rawTask = RawGet(fields, _config.ColTask);
                var rawIssue = RawGet(fields, _config.ColIssue);

                var ticket = new ExternalTicket
                {
                    Source = "ntt",
                    Timestamp = SafeGetDate(fields, _config.ColTimestamp),
                    RequesterEmail = SafeGet(fields, _config.ColEmail),
                    RequesterName = SafeGet(fields, _config.ColRequestedBy),
                    TaskTitle = SafeGet(fields, _config.ColTask),
                    DeviceName = SafeGet(fields, _config.ColTask),
                    Location = SafeGet(fields, _config.ColLocation),
                    IssueDescription = SafeGet(fields, _config.ColIssue) ?? SafeGet(fields, _config.ColTask),
                    RawPriority = SafeGet(fields, _config.ColPriority),
                    RawStatus = SafeGet(fields, _config.ColStatus),
                    AssignedTo = SafeGet(fields, _config.ColAssignedTo),
                    PreferredDate = SafeGetDateNullable(fields, _config.ColPreferredDate),
                    SheetNotes = SafeGet(fields, _config.ColNotes)
                };

                var stableHash = GenerateStableHash(rawTimestamp, rawEmail, rawTask, rawIssue);
                ticket.InternalId = StableIdFromHash(stableHash, usedIds);
                ticket.ExternalId = "NTT" + ticket.InternalId.ToString();
                usedIds.Add(ticket.InternalId);

                // Use Contains for flexible status matching
                var status = (ticket.RawStatus ?? "").ToLower().Trim();
                ticket.IsOpen = !status.Contains("complete") && !status.Contains("closed")
                    && !status.Contains("resolved") && !status.Contains("done")
                    && !status.Contains("cancel") && !status.Contains("finished");

                if (ticket.IsOpen && (!string.IsNullOrWhiteSpace(ticket.TaskTitle) || !string.IsNullOrWhiteSpace(ticket.IssueDescription)))
                    tickets.Add(ticket);
            }
            return tickets;
        }

        private int GenerateStableHash(string rawTimestamp, string rawEmail, string rawTask, string rawIssue)
        {
            var key = (rawTimestamp ?? "").Trim().ToLower() + "|" + (rawEmail ?? "").Trim().ToLower() + "|" + (rawTask ?? "").Trim().ToLower() + "|" + (rawIssue ?? "").Trim().ToLower();
            uint hash = 5381;
            for (int i = 0; i < key.Length; i++) hash = ((hash << 5) + hash) + (uint)key[i];
            return (int)(hash % 800000) + 100000;
        }

        private int StableIdFromHash(int baseId, HashSet<int> used) { int id = baseId; while (used.Contains(id)) id++; return id; }
        private string RawGet(List<string> fields, int index) { if (index < 0 || index >= fields.Count) return ""; return fields[index] ?? ""; }

        public static string MapPriority(string raw)
        {
            if (string.IsNullOrEmpty(raw)) return "medium";
            var lower = raw.ToLower().Trim();
            if (lower.Contains("urgent") || lower.Contains("same day") || lower.Contains("critical")) return "critical";
            if (lower.Contains("high") || lower.Contains("1-2 day")) return "high";
            if (lower.Contains("medium") || lower.Contains("3-5 day")) return "medium";
            if (lower.Contains("low") || lower.Contains("1 week") || lower.Contains("week+")) return "low";
            if (lower.Contains("scheduled") || lower.Contains("planned")) return "scheduled";
            return "medium";
        }

        private string SafeGet(List<string> fields, int index) { if (index < 0 || index >= fields.Count) return null; var val = fields[index].Trim(); return string.IsNullOrEmpty(val) ? null : val; }
        private DateTime SafeGetDate(List<string> fields, int index) { var val = SafeGet(fields, index); if (val == null) return DateTime.MinValue; DateTime dt; if (DateTime.TryParse(val, out dt)) return dt; return DateTime.MinValue; }
        private DateTime? SafeGetDateNullable(List<string> fields, int index) { var val = SafeGet(fields, index); if (val == null) return null; DateTime dt; if (DateTime.TryParse(val, out dt)) return dt; return null; }

        private List<string> ParseCsvLine(string line)
        {
            var fields = new List<string>(); bool inQuotes = false; var current = new StringBuilder();
            for (int i = 0; i < line.Length; i++) { char c = line[i]; if (c == '"') { if (inQuotes && i + 1 < line.Length && line[i + 1] == '"') { current.Append('"'); i++; } else inQuotes = !inQuotes; } else if (c == ',' && !inQuotes) { fields.Add(current.ToString()); current.Clear(); } else if (c != '\r') current.Append(c); }
            fields.Add(current.ToString()); return fields;
        }
    }

    public class GoogleSheetResult
    {
        public List<ExternalTicket> Tickets { get; set; }
        public string Error { get; set; }
        public string Warning { get; set; }
        public GoogleSheetResult() { Tickets = new List<ExternalTicket>(); }
    }
}