using System;
using System.IO;
using System.IO.Ports;
using System.Text;
using System.Threading.Tasks;

namespace Elwig.Helpers.Weighing {
    public class SysTecITScale : Scale, ICommandScale {

        public string Manufacturer => "SysTec";
        public int InternalScaleNr => 1;
        public string Model { get; private set; }
        public string ScaleId { get; private set; }
        public bool IsReady { get; private set; }
        public bool HasFillingClearance { get; private set; }

        public SysTecITScale(string id, string model, string cnx, string? empty = null, string? filling = null, int? limit = null, string? log = null) :
            base(cnx, empty, filling, limit, log) {
            ScaleId = id;
            Model = model;
            IsReady = true;
            HasFillingClearance = false;
            Stream.WriteTimeout = 250;
            Stream.ReadTimeout = 11000;
        }

        protected async Task SendCommand(string command) {
            byte[] bytes = Encoding.ASCII.GetBytes($"<{command}>");
            await Stream.WriteAsync(bytes);
            if (LogPath != null) await File.AppendAllTextAsync(LogPath, $"<{command}>");
        }

        protected async Task<string> ReceiveResponse() {
            var line = await Reader.ReadUntilAsync("\r\n");
            if (LogPath != null) await File.AppendAllTextAsync(LogPath, line);
            if (line == null || line.Length < 4 || !line.StartsWith('<') || !line.EndsWith(">\r\n")) {
                throw new IOException("Invalid response from scale");
            }

            var error = line[1..3];
            if (error[0] == '0') {
                if (error[1] != '0') {
                    throw new IOException($"Invalid response from scale (error code {error})");
                }
            } else if (error[0] == '1') {
                string msg = $"Unbekannter Fehler (Fehler code {error})";
                switch (error[1]) {
                    case '1': msg = "Allgemeiner Waagenfehler"; break;
                    case '2': msg = "Waage in Überlast"; break;
                    case '3': msg = "Waage in Bewegung"; break;
                    case '5': msg = "Tarierungs- oder Nullsetzfehler"; break;
                    case '6': msg = "Drucker nicht bereit"; break;
                    case '7': msg = "Druckmuster enthält ungültiges Kommando"; break;
                }
                throw new IOException($"Waagenfehler {error}: {msg}");
            } else if (error[0] == '3') {
                string msg = $"Unbekannter Fehler (Fehler code {error})";
                switch (error[1]) {
                    case '1': msg = "Übertragunsfehler"; break;
                    case '2': msg = "Ungültiger Befehl"; break;
                    case '3': msg = "Ungültiger Parameter"; break;
                }
                throw new IOException($"Kommunikationsfehler {error}: {msg}");
            } else {
                throw new IOException($"Invalid response from scale (error code {error})");
            }

            return line[1..^3];
        }

        protected async Task<WeighingResult> Weigh(bool incIdentNr) {
            await SendCommand(incIdentNr ? $"RN{InternalScaleNr}" : $"RM{InternalScaleNr}");
            string record = await ReceiveResponse();
            if (record.Length != 62)
                throw new IOException("Invalid response from scale: Received record has invalid size");
            var line = record[2..];

            var status     = line[ 0.. 2];
            var date       = line[ 2..10];
            var time       = line[10..15];
            var identNr    = line[15..19].Trim();
            var scaleNr    = line[19..20].Trim();
            var brutto     = line[20..28].Trim();
            var tara       = line[28..36].Trim();
            var netto      = line[36..44].Trim();
            var unit       = line[44..46];
            var taraCode   = line[46..48];
            var zone       = line[48..49].Trim();
            var terminalNr = line[49..52].Trim();
            var crc16      = line[52..60].Trim();

            if (Utils.CalcCrc16Modbus(record[..54]) != ushort.Parse(crc16)) {
                throw new IOException($"Invalid response from scale: Invalid CRC16 checksum ({crc16} != {Utils.CalcCrc16Modbus(record[..54])})");
            } else if (unit != "kg") {
                throw new IOException($"Unsupported unit in weighing response: '{unit}'");
            }

            identNr = identNr.Length > 0 && identNr != "0" ? identNr : null;
            var parsedDate = DateOnly.Parse(date);
            return new() {
                GrossWeight = int.Parse(brutto),
                TareWeight = int.Parse(tara),
                NetWeight = int.Parse(netto),
                WeighingId = identNr,
                FullWeighingId = identNr != null ? $"{parsedDate:yyyy-MM-dd}/{identNr}" : null,
                Date = parsedDate,
                Time = TimeOnly.Parse(time),
            };
        }

        public async Task<WeighingResult> Weigh() {
            return await Weigh(true);
        }

        public async Task<WeighingResult> GetCurrentWeight() {
            return await Weigh(false);
        }

        public async Task Empty() {
            SerialPort? p = ControlSerialEmpty ?? Serial;
            if (EmptyMode == Output.RTS && p != null) {
                p.RtsEnable = true;
                await Task.Delay(EmptyDelay);
                p.RtsEnable = false;
            } else if (EmptyMode == Output.DTR && p != null) {
                p.DtrEnable = true;
                await Task.Delay(EmptyDelay);
                p.DtrEnable = false;
            } else if (EmptyMode == Output.OUT1 || EmptyMode == Output.OUT2) {
                int output = EmptyMode == Output.OUT1 ? 1 : 2;
                await SendCommand($"OS{output:00}");
                await ReceiveResponse();
                await Task.Delay(EmptyDelay);
                await SendCommand($"OC{output:00}");
                await ReceiveResponse();
            }
        }

        protected async Task SetFillingClearance(bool status) {
            SerialPort? p = ControlSerialFilling ?? Serial;
            if (FillingClearanceMode == Output.RTS && p != null) {
                p.RtsEnable = status;
            } else if (FillingClearanceMode == Output.DTR && p != null) {
                p.DtrEnable = status;
            } else if (FillingClearanceMode == Output.OUT1 || FillingClearanceMode == Output.OUT2) {
                string cmd = status ? "OS" : "OC";
                int output = FillingClearanceMode == Output.OUT1 ? 1 : 2;
                await SendCommand($"{cmd}{output:00}");
                await ReceiveResponse();
            }
        }

        public async Task GrantFillingClearance() {
            await SetFillingClearance(true);
        }

        public async Task RevokeFillingClearance() {
            await SetFillingClearance(false);
        }
    }
}