using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
using UnityEngine.Networking;
using UnityEngine;
using Verse;
using System.Linq;

namespace WulaFallenEmpire.EventSystem.AI
{
    public class SimpleAIClient
    {
        private readonly string _apiKey;
        private readonly string _baseUrl;
        private readonly string _model;
        private readonly bool _useGemini;
        private const int MaxLogChars = 2000;

        public SimpleAIClient(string apiKey, string baseUrl, string model, bool useGemini = false)
        {
            _apiKey = apiKey;
            _baseUrl = baseUrl?.TrimEnd('/');
            _model = model;
            _useGemini = useGemini;
        }

        public async Task<string> GetChatCompletionAsync(string instruction, List<(string role, string message)> messages, int? maxTokens = null, float? temperature = null, string base64Image = null)
        {
            if (_useGemini)
            {
                return await GetGeminiCompletionAsync(instruction, messages, maxTokens, temperature, base64Image);
            }

            // OpenAI / Compatible Mode
            if (string.IsNullOrEmpty(_baseUrl))
            {
                WulaLog.Debug("[WulaAI] Base URL is missing.");
                return null;
            }

            string endpoint = $"{_baseUrl}/chat/completions";
            if (_baseUrl.EndsWith("/chat/completions")) endpoint = _baseUrl;
            else if (!_baseUrl.EndsWith("/v1")) endpoint = $"{_baseUrl}/v1/chat/completions";

            StringBuilder jsonBuilder = new StringBuilder();
            jsonBuilder.Append("{");
            jsonBuilder.Append($"\"model\": \"{_model}\",");
            jsonBuilder.Append("\"stream\": false,");
            if (maxTokens.HasValue) jsonBuilder.Append($"\"max_tokens\": {Math.Max(1, maxTokens.Value)},");
            if (temperature.HasValue) jsonBuilder.Append($"\"temperature\": {temperature.Value.ToString("0.###", System.Globalization.CultureInfo.InvariantCulture)},");
            
            jsonBuilder.Append("\"messages\": [");
            if (!string.IsNullOrEmpty(instruction))
            {
                jsonBuilder.Append($"{{\"role\": \"system\", \"content\": \"{EscapeJson(instruction)}\"}},");
            }

            for (int i = 0; i < messages.Count; i++)
            {
                var msg = messages[i];
                string role = (msg.role ?? "user").ToLowerInvariant();
                if (role == "ai" || role == "assistant") role = "assistant";
                else if (role == "tool") role = "system";
                else if (role == "toolcall") continue;
                
                jsonBuilder.Append($"{{\"role\": \"{role}\", ");
                
                if (i == messages.Count - 1 && role == "user" && !string.IsNullOrEmpty(base64Image))
                {
                    jsonBuilder.Append("\"content\": [");
                    jsonBuilder.Append($"{{\"type\": \"text\", \"text\": \"{EscapeJson(msg.message)}\"}},");
                    jsonBuilder.Append($"{{\"type\": \"image_url\", \"image_url\": {{\"url\": \"data:image/png;base64,{base64Image}\"}}}}");
                    jsonBuilder.Append("]");
                }
                else
                {
                    jsonBuilder.Append($"\"content\": \"{EscapeJson(msg.message)}\"");
                }
                
                jsonBuilder.Append("}");
                if (i < messages.Count - 1) jsonBuilder.Append(",");
            }
            jsonBuilder.Append("]}");

            return await SendRequestAsync(endpoint, jsonBuilder.ToString(), _apiKey);
        }

        private async Task<string> GetGeminiCompletionAsync(string instruction, List<(string role, string message)> messages, int? maxTokens = null, float? temperature = null, string base64Image = null)
        {
            // Gemini API URL
            string baseUrl = _baseUrl;
            if (string.IsNullOrEmpty(baseUrl) || !baseUrl.Contains("googleapis.com"))
            {
                baseUrl = "https://generativelanguage.googleapis.com/v1beta";
            }

            string endpoint = $"{baseUrl}/models/{_model}:generateContent?key={_apiKey}";
            
            StringBuilder jsonBuilder = new StringBuilder();
            jsonBuilder.Append("{");
            
            if (!string.IsNullOrEmpty(instruction))
            {
                jsonBuilder.Append("\"system_instruction\": {\"parts\": [{\"text\": \"" + EscapeJson(instruction) + "\"}]},");
            }

            jsonBuilder.Append("\"contents\": [");
            for (int i = 0; i < messages.Count; i++)
            {
                var msg = messages[i];
                string role = (msg.role ?? "user").ToLowerInvariant();
                if (role == "assistant" || role == "ai") role = "model";
                else role = "user";

                jsonBuilder.Append($"{{\"role\": \"{role}\", \"parts\": [");
                jsonBuilder.Append($"{{\"text\": \"{EscapeJson(msg.message)}\"}}");
                
                if (i == messages.Count - 1 && role == "user" && !string.IsNullOrEmpty(base64Image))
                {
                    jsonBuilder.Append($", {{\"inline_data\": {{\"mime_type\": \"image/png\", \"data\": \"{base64Image}\"}}}}");
                }

                jsonBuilder.Append("]}");
                if (i < messages.Count - 1) jsonBuilder.Append(",");
            }
            jsonBuilder.Append("],");

            jsonBuilder.Append("\"generationConfig\": {");
            if (temperature.HasValue) jsonBuilder.Append($"\"temperature\": {temperature.Value.ToString("0.###", System.Globalization.CultureInfo.InvariantCulture)},");
            if (maxTokens.HasValue) jsonBuilder.Append($"\"maxOutputTokens\": {maxTokens.Value}");
            else jsonBuilder.Append("\"maxOutputTokens\": 2048");
            jsonBuilder.Append("}");

            jsonBuilder.Append("}");

            return await SendRequestAsync(endpoint, jsonBuilder.ToString(), null);
        }

        private async Task<string> SendRequestAsync(string endpoint, string jsonBody, string apiKey)
        {
            if (Prefs.DevMode)
            {
                WulaLog.Debug($"[WulaAI] Sending request to {endpoint}");
            }

            using (UnityWebRequest request = new UnityWebRequest(endpoint, "POST"))
            {
                byte[] bodyRaw = Encoding.UTF8.GetBytes(jsonBody);
                request.uploadHandler = new UploadHandlerRaw(bodyRaw);
                request.downloadHandler = new DownloadHandlerBuffer();
                request.SetRequestHeader("Content-Type", "application/json");
                if (!string.IsNullOrEmpty(apiKey))
                {
                    request.SetRequestHeader("Authorization", $"Bearer {apiKey}");
                }
                request.timeout = 60;

                var operation = request.SendWebRequest();
                while (!operation.isDone) await Task.Delay(50);

                if (request.result != UnityWebRequest.Result.Success)
                {
                    string errText = request.downloadHandler.text;
                    WulaLog.Debug($"[WulaAI] API Error ({request.responseCode}): {request.error}\nResponse: {TruncateForLog(errText)}");
                    return null;
                }

                string response = request.downloadHandler.text;
                return ExtractContent(response);
            }
        }

        private string ExtractContent(string json)
        {
            if (string.IsNullOrWhiteSpace(json)) return null;

            try
            {
                // 1. Gemini format
                if (json.Contains("\"candidates\""))
                {
                    int partsIndex = json.IndexOf("\"parts\"", StringComparison.Ordinal);
                    if (partsIndex != -1) return ExtractJsonValue(json, "text", partsIndex);
                }

                // 2. OpenAI format
                if (json.Contains("\"choices\""))
                {
                    int choicesIndex = json.IndexOf("\"choices\"", StringComparison.Ordinal);
                    string firstChoice = TryExtractFirstChoiceObject(json, choicesIndex);
                    if (!string.IsNullOrEmpty(firstChoice))
                    {
                        int messageIndex = firstChoice.IndexOf("\"message\"", StringComparison.Ordinal);
                        if (messageIndex != -1) return ExtractJsonValue(firstChoice, "content", messageIndex);
                        
                        int deltaIndex = firstChoice.IndexOf("\"delta\"", StringComparison.Ordinal);
                        if (deltaIndex != -1) return ExtractJsonValue(firstChoice, "content", deltaIndex);

                        return ExtractJsonValue(firstChoice, "text", 0);
                    }
                }

                // 3. Last fallback
                return ExtractJsonValue(json, "content");
            }
            catch (Exception ex)
            {
                WulaLog.Debug($"[WulaAI] Error parsing response: {ex.Message}");
            }
            return null;
        }

        private static string TryExtractFirstChoiceObject(string json, int choicesKeyIndex)
        {
            int arrayStart = json.IndexOf('[', choicesKeyIndex);
            if (arrayStart == -1) return null;
            int objStart = json.IndexOf('{', arrayStart);
            if (objStart == -1) return null;
            int objEnd = FindMatchingBrace(json, objStart);
            if (objEnd == -1) return null;
            return json.Substring(objStart, objEnd - objStart + 1);
        }

        private static int FindMatchingBrace(string json, int startIndex)
        {
            int depth = 0;
            bool inString = false;
            bool escaped = false;
            for (int i = startIndex; i < json.Length; i++)
            {
                char c = json[i];
                if (inString)
                {
                    if (escaped) { escaped = false; continue; }
                    if (c == '\\') { escaped = true; continue; }
                    if (c == '"') inString = false;
                    continue;
                }
                if (c == '"') { inString = true; continue; }
                if (c == '{') depth++;
                if (c == '}') { depth--; if (depth == 0) return i; }
            }
            return -1;
        }

        private static string ExtractJsonValue(string json, string key, int startIndex = 0)
        {
            string keyPattern = $"\"{key}\"";
            int keyIndex = json.IndexOf(keyPattern, startIndex, StringComparison.Ordinal);
            if (keyIndex == -1) return null;

            int colonIndex = json.IndexOf(':', keyIndex + keyPattern.Length);
            if (colonIndex == -1) return null;

            int valueStart = json.IndexOf('"', colonIndex);
            if (valueStart == -1) return null;

            StringBuilder sb = new StringBuilder();
            bool escaped = false;
            for (int i = valueStart + 1; i < json.Length; i++)
            {
                char c = json[i];
                if (escaped)
                {
                    if (c == 'n') sb.Append('\n');
                    else if (c == 'r') sb.Append('\r');
                    else if (c == 't') sb.Append('\t');
                    else if (c == '"') sb.Append('"');
                    else if (c == '\\') sb.Append('\\');
                    else sb.Append(c);
                    escaped = false;
                }
                else
                {
                    if (c == '\\') escaped = true;
                    else if (c == '"') return sb.ToString();
                    else sb.Append(c);
                }
            }
            return null;
        }

        private string EscapeJson(string s)
        {
            if (s == null) return "";
            StringBuilder sb = new StringBuilder(s.Length + 16);
            for (int i = 0; i < s.Length; i++)
            {
                char c = s[i];
                switch (c)
                {
                    case '\\': sb.Append("\\\\"); break;
                    case '"': sb.Append("\\\""); break;
                    case '\n': sb.Append("\\n"); break;
                    case '\r': sb.Append("\\r"); break;
                    case '\t': sb.Append("\\t"); break;
                    default:
                        if (c < 0x20) { sb.Append("\\u"); sb.Append(((int)c).ToString("x4")); }
                        else sb.Append(c);
                        break;
                }
            }
            return sb.ToString();
        }

        private static string TruncateForLog(string s)
        {
            if (string.IsNullOrEmpty(s)) return s;
            if (s.Length <= MaxLogChars) return s;
            return s.Substring(0, MaxLogChars) + "... (truncated)";
        }
    }
}