using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using GeViSetEditor.Core.Models;

namespace GeViSetEditor.Core.Parsers
{
    /// <summary>
    /// Enhanced parser that extracts full configuration structure
    /// while preserving original binary data for round-trip conversion
    /// </summary>
    public class EnhancedSetFileParser
    {
        private byte[] _originalData;
        private int _position;

        public EnhancedSetFile Parse(byte[] data)
        {
            _originalData = data;
            _position = 0;

            var setFile = new EnhancedSetFile
            {
                OriginalData = data,
                FileSize = data.Length
            };

            Console.WriteLine($"\n=== Enhanced Configuration Parser ===");
            Console.WriteLine($"File size: {data.Length:N0} bytes\n");

            // Read header
            if (_position < data.Length && data[_position] == 0x00)
                _position++;

            string header = ReadPascalString();
            setFile.Header = header ?? "GeViSoft Parameters";
            Console.WriteLine($"Header: '{setFile.Header}'");

            // Extract configuration items (key-value pairs)
            ExtractConfigItems(setFile);

            // Extract action mappings
            ExtractActionMappings(setFile);

            // Extract section names
            ExtractSectionNames(setFile);

            Console.WriteLine($"\n=== Parse Summary ===");
            Console.WriteLine($"Configuration items: {setFile.ConfigItems.Count}");
            Console.WriteLine($"Action mappings: {setFile.ActionMappings.Count}");
            Console.WriteLine($"Section names: {setFile.SectionNames.Count}");

            return setFile;
        }

        private void ExtractConfigItems(EnhancedSetFile setFile)
        {
            Console.WriteLine("\nExtracting configuration items...");

            // Look for key-value patterns
            // Common pattern: Pascal string (key) followed by typed value
            for (int i = 0; i < _originalData.Length - 10; i++)
            {
                var item = TryReadConfigItem(i);
                if (item != null && !string.IsNullOrWhiteSpace(item.Key))
                {
                    setFile.ConfigItems.Add(item);
                }
            }

            Console.WriteLine($"Found {setFile.ConfigItems.Count} config items");
        }

        private ConfigItemEntry TryReadConfigItem(int offset)
        {
            try
            {
                // Skip if this looks like part of an action mapping
                if (IsNearRulesMarker(offset, 100))
                    return null;

                // Skip if in the first 1000 bytes (header area)
                if (offset < 1000)
                    return null;

                // Try to read Pascal string as key
                int pos = offset;

                // Look for string marker (0x07) followed by reasonable length
                if (pos >= _originalData.Length || _originalData[pos] != 0x07)
                    return null;

                pos++;
                if (pos >= _originalData.Length)
                    return null;

                byte keyLen = _originalData[pos];
                if (keyLen < 3 || keyLen > 50)  // More restrictive length
                    return null;

                pos++;
                if (pos + keyLen > _originalData.Length)
                    return null;

                string key = Encoding.UTF8.GetString(_originalData, pos, keyLen);

                // Check if key looks valid (must be clean identifier)
                if (!IsValidConfigKey(key))
                    return null;

                // Key must not contain common section names (avoid duplicates)
                string keyLower = key.ToLower();
                if (keyLower.Contains("rules") || keyLower.Contains("action") ||
                    keyLower.Contains("gsc") || keyLower.Contains("gng"))
                    return null;

                pos += keyLen;

                // Must be followed immediately by typed value marker
                if (pos >= _originalData.Length)
                    return null;

                byte typeMarker = _originalData[pos];
                if (typeMarker != 0x01 && typeMarker != 0x04 && typeMarker != 0x07)
                    return null;

                // Try to read value
                var (value, valueType, bytesRead) = TryReadTypedValue(pos);
                if (value == null || bytesRead == 0)
                    return null;

                return new ConfigItemEntry
                {
                    FileOffset = offset,
                    Key = key,
                    Value = value,
                    ValueType = valueType
                };
            }
            catch
            {
                return null;
            }
        }

        private (object value, string type, int bytesRead) TryReadTypedValue(int pos)
        {
            if (pos >= _originalData.Length)
                return (null, null, 0);

            byte typeMarker = _originalData[pos];

            try
            {
                switch (typeMarker)
                {
                    case 0x01: // Boolean
                        if (pos + 2 <= _originalData.Length)
                        {
                            bool value = _originalData[pos + 1] != 0;
                            return (value, "boolean", 2);
                        }
                        break;

                    case 0x04: // Integer (4 bytes)
                        if (pos + 5 <= _originalData.Length)
                        {
                            int value = BitConverter.ToInt32(_originalData, pos + 1);
                            return (value, "integer", 5);
                        }
                        break;

                    case 0x07: // String (Pascal string)
                        pos++;
                        if (pos >= _originalData.Length)
                            break;

                        byte strLen = _originalData[pos];
                        if (strLen > 0 && strLen < 200 && pos + 1 + strLen <= _originalData.Length)
                        {
                            string value = Encoding.UTF8.GetString(_originalData, pos + 1, strLen);
                            if (IsValidStringValue(value))
                            {
                                return (value, "string", 2 + strLen);
                            }
                        }
                        break;
                }
            }
            catch
            {
                // Ignore parse errors
            }

            return (null, null, 0);
        }

        private bool IsValidConfigKey(string key)
        {
            if (string.IsNullOrWhiteSpace(key))
                return false;

            // Must not be too long
            if (key.Length > 40)
                return false;

            // No control characters except spaces
            if (key.Any(c => char.IsControl(c)))
                return false;

            // Should contain mostly alphanumeric or underscores
            int validChars = key.Count(c => char.IsLetterOrDigit(c) || c == '_' || c == '-');

            // At least 90% valid chars (more strict)
            if (validChars < key.Length * 0.9)
                return false;

            // Must start with a letter or underscore
            if (!char.IsLetter(key[0]) && key[0] != '_')
                return false;

            // Common patterns that indicate it's not a config key
            if (key.Contains("  ") || key.Contains("\t"))
                return false;

            return true;
        }

        private bool IsValidStringValue(string value)
        {
            if (string.IsNullOrEmpty(value))
                return true; // Empty strings are valid

            // Check for excessive control characters
            int controlChars = value.Count(c => char.IsControl(c) && c != '\r' && c != '\n' && c != '\t');
            return controlChars < value.Length * 0.3; // Less than 30% control chars
        }

        private bool IsNearRulesMarker(int offset, int distance)
        {
            // Check if there's a "Rules" marker nearby
            byte[] rulesPattern = new byte[] { 0x05, 0x52, 0x75, 0x6C, 0x65, 0x73 };

            int start = Math.Max(0, offset - distance);
            int end = Math.Min(_originalData.Length - rulesPattern.Length, offset + distance);

            for (int i = start; i < end; i++)
            {
                if (MatchesPattern(_originalData, i, rulesPattern))
                    return true;
            }

            return false;
        }

        private void ExtractActionMappings(EnhancedSetFile setFile)
        {
            Console.WriteLine("\nExtracting action mappings...");

            // Search for all "Rules" patterns (05 52 75 6C 65 73)
            byte[] rulesPattern = new byte[] { 0x05, 0x52, 0x75, 0x6C, 0x65, 0x73 };

            for (int i = 0; i < _originalData.Length - rulesPattern.Length - 100; i++)
            {
                if (MatchesPattern(_originalData, i, rulesPattern))
                {
                    var mapping = TryExtractActionMapping(i);
                    if (mapping != null)
                    {
                        setFile.ActionMappings.Add(mapping);
                    }
                }
            }

            Console.WriteLine($"Found {setFile.ActionMappings.Count} action mappings");
        }

        private ActionMappingEntry TryExtractActionMapping(int rulesOffset)
        {
            try
            {
                var entry = new ActionMappingEntry
                {
                    FileOffset = rulesOffset,
                    RulesMarkerOffset = rulesOffset
                };

                // Position after "Rules" marker
                int pos = rulesOffset + 6; // Skip "05 Rules"

                if (pos + 10 > _originalData.Length) return null;

                // Skip metadata bytes (usually 0x00-0x04)
                while (pos < _originalData.Length && _originalData[pos] <= 0x04)
                {
                    pos++;
                }

                int actionDataStart = pos;

                // Extract action strings using pattern 07 01 40 <len_2bytes> <data>
                var actions = new List<string>();
                int consecutiveFailures = 0;
                int maxAttempts = 200;

                while (maxAttempts-- > 0 && pos < _originalData.Length - 10)
                {
                    var action = TryReadActionStringAt(pos);
                    if (action != null)
                    {
                        actions.Add(action);
                        pos += 5 + Encoding.UTF8.GetByteCount(action);
                        consecutiveFailures = 0;
                    }
                    else
                    {
                        pos++;
                        consecutiveFailures++;
                        if (consecutiveFailures > 100) break;
                    }
                }

                if (actions.Count > 0)
                {
                    entry.Actions = actions;
                    entry.ActionDataStartOffset = actionDataStart;
                    entry.ActionDataEndOffset = pos;

                    // Store original bytes
                    int length = pos - rulesOffset;
                    entry.OriginalBytes = new byte[length];
                    Array.Copy(_originalData, rulesOffset, entry.OriginalBytes, 0, length);

                    return entry;
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error at offset {rulesOffset}: {ex.Message}");
            }

            return null;
        }

        private string TryReadActionStringAt(int pos)
        {
            // Pattern: 07 01 40 <len_2bytes_LE> <data>
            if (pos + 5 > _originalData.Length) return null;

            if (_originalData[pos] != 0x07 ||
                _originalData[pos + 1] != 0x01 ||
                _originalData[pos + 2] != 0x40)
                return null;

            ushort length = BitConverter.ToUInt16(_originalData, pos + 3);
            if (length == 0 || length > 500 || pos + 5 + length > _originalData.Length)
                return null;

            try
            {
                string result = Encoding.UTF8.GetString(_originalData, pos + 5, length);

                // Validate it looks like an action string
                if (result.Length > 3 && result.All(c => c >= 32 || c == '\t' || c == '\n' || c == '\r'))
                {
                    return result;
                }
            }
            catch
            {
                // Ignore decode errors
            }

            return null;
        }

        private void ExtractSectionNames(EnhancedSetFile setFile)
        {
            Console.WriteLine("\nExtracting section names...");

            // Look for Pascal strings that appear to be section names
            // Characteristics: reasonable length (5-50 chars), mostly alphanumeric
            HashSet<string> foundNames = new HashSet<string>();

            for (int i = 0; i < _originalData.Length - 10; i++)
            {
                if (_originalData[i] == 0x07) // String marker
                {
                    i++;
                    if (i >= _originalData.Length)
                        break;

                    byte len = _originalData[i];
                    if (len >= 5 && len <= 50 && i + 1 + len <= _originalData.Length)
                    {
                        try
                        {
                            string name = Encoding.UTF8.GetString(_originalData, i + 1, len);

                            // Check if it looks like a section name
                            if (IsLikelySectionName(name) && !foundNames.Contains(name))
                            {
                                foundNames.Add(name);
                                setFile.SectionNames.Add(new SectionNameEntry
                                {
                                    FileOffset = i - 1,
                                    Name = name
                                });
                            }
                        }
                        catch
                        {
                            // Ignore decode errors
                        }
                    }
                }
            }

            Console.WriteLine($"Found {setFile.SectionNames.Count} unique section names");
        }

        private bool IsLikelySectionName(string name)
        {
            if (string.IsNullOrWhiteSpace(name))
                return false;

            // Should be mostly letters, numbers, underscores
            // Common section names: "Alarms", "Cameras", "GeViIO", "Description", "Name", "IpHost"
            int validChars = name.Count(c => char.IsLetterOrDigit(c) || c == '_' || c == ' ');

            // At least 80% valid characters
            return validChars >= name.Length * 0.8;
        }

        private string ReadPascalString()
        {
            if (_position >= _originalData.Length)
                return null;

            byte length = _originalData[_position++];
            if (length == 0 || _position + length > _originalData.Length)
                return null;

            string result = Encoding.UTF8.GetString(_originalData, _position, length);
            _position += length;
            return result;
        }

        private bool MatchesPattern(byte[] data, int offset, byte[] pattern)
        {
            if (offset + pattern.Length > data.Length)
                return false;

            for (int i = 0; i < pattern.Length; i++)
            {
                if (data[offset + i] != pattern[i])
                    return false;
            }

            return true;
        }
    }
}