package handlers

import (
	"cursor-api-proxy/internal/agent"
	"cursor-api-proxy/internal/config"
	"cursor-api-proxy/internal/httputil"
	"cursor-api-proxy/internal/logger"
	"cursor-api-proxy/internal/models"
	"cursor-api-proxy/internal/openai"
	"cursor-api-proxy/internal/parser"
	"cursor-api-proxy/internal/pool"
	"cursor-api-proxy/internal/sanitize"
	"cursor-api-proxy/internal/winlimit"
	"cursor-api-proxy/internal/workspace"
	"encoding/json"
	"fmt"
	"net/http"
	"regexp"
	"time"

	"github.com/google/uuid"
)

var rateLimitRe = regexp.MustCompile(`(?i)\b429\b|rate.?limit|too many requests`)

func isRateLimited(stderr string) bool {
	return rateLimitRe.MatchString(stderr)
}

func HandleChatCompletions(w http.ResponseWriter, r *http.Request, cfg config.BridgeConfig, lastModelRef *string, rawBody, method, pathname, remoteAddress string) {
	var bodyMap map[string]interface{}
	if err := json.Unmarshal([]byte(rawBody), &bodyMap); err != nil {
		httputil.WriteJSON(w, 400, map[string]interface{}{
			"error": map[string]string{"message": "invalid JSON body", "code": "bad_request"},
		}, nil)
		return
	}

	rawModel, _ := bodyMap["model"].(string)
	requested := openai.NormalizeModelID(rawModel)
	model := ResolveModel(requested, lastModelRef, cfg)
	cursorModel := models.ResolveToCursorModel(model)
	if cursorModel == "" {
		cursorModel = model
	}

	var messages []interface{}
	if m, ok := bodyMap["messages"].([]interface{}); ok {
		messages = m
	}

	var tools []interface{}
	if t, ok := bodyMap["tools"].([]interface{}); ok {
		tools = t
	}
	var funcs []interface{}
	if f, ok := bodyMap["functions"].([]interface{}); ok {
		funcs = f
	}

	cleanMessages := sanitize.SanitizeMessages(messages)

	toolsText := openai.ToolsToSystemText(tools, funcs)
	messagesWithTools := cleanMessages
	if toolsText != "" {
		messagesWithTools = append([]interface{}{map[string]interface{}{"role": "system", "content": toolsText}}, cleanMessages...)
	}
	prompt := openai.BuildPromptFromMessages(messagesWithTools)

	var trafficMsgs []logger.TrafficMessage
	for _, raw := range cleanMessages {
		if m, ok := raw.(map[string]interface{}); ok {
			role, _ := m["role"].(string)
			content := openai.MessageContentToText(m["content"])
			trafficMsgs = append(trafficMsgs, logger.TrafficMessage{Role: role, Content: content})
		}
	}

	isStream := false
	if s, ok := bodyMap["stream"].(bool); ok {
		isStream = s
	}

	logger.LogTrafficRequest(cfg.Verbose, model, trafficMsgs, isStream)

	headerWs := r.Header.Get("x-cursor-workspace")
	ws := workspace.ResolveWorkspace(cfg, headerWs)

	fixedArgs := agent.BuildAgentFixedArgs(cfg, ws.WorkspaceDir, cursorModel, isStream)
	fit := winlimit.FitPromptToWinCmdline(cfg.AgentBin, fixedArgs, prompt, cfg.WinCmdlineMax, ws.WorkspaceDir)

	if !fit.OK {
		httputil.WriteJSON(w, 500, map[string]interface{}{
			"error": map[string]string{"message": fit.Error, "code": "windows_cmdline_limit"},
		}, nil)
		return
	}
	if fit.Truncated {
		logger.LogTruncation(fit.OriginalLength, fit.FinalPromptLength)
	}

	cmdArgs := fit.Args
	id := "chatcmpl_" + uuid.New().String()
	created := time.Now().Unix()

	var truncatedHeaders map[string]string
	if fit.Truncated {
		truncatedHeaders = map[string]string{"X-Cursor-Proxy-Prompt-Truncated": "true"}
	}

	if isStream {
		httputil.WriteSSEHeaders(w, truncatedHeaders)
		flusher, _ := w.(http.Flusher)

		var accumulated string
		parseLine := parser.CreateStreamParser(
			func(text string) {
				accumulated += text
				chunk := map[string]interface{}{
					"id":      id,
					"object":  "chat.completion.chunk",
					"created": created,
					"model":   model,
					"choices": []map[string]interface{}{
						{"index": 0, "delta": map[string]string{"content": text}, "finish_reason": nil},
					},
				}
				data, _ := json.Marshal(chunk)
				fmt.Fprintf(w, "data: %s\n\n", data)
				if flusher != nil {
					flusher.Flush()
				}
			},
			func() {
				logger.LogTrafficResponse(cfg.Verbose, model, accumulated, true)
				stopChunk := map[string]interface{}{
					"id":      id,
					"object":  "chat.completion.chunk",
					"created": created,
					"model":   model,
					"choices": []map[string]interface{}{
						{"index": 0, "delta": map[string]interface{}{}, "finish_reason": "stop"},
					},
				}
				data, _ := json.Marshal(stopChunk)
				fmt.Fprintf(w, "data: %s\n\n", data)
				fmt.Fprintf(w, "data: [DONE]\n\n")
				if flusher != nil {
					flusher.Flush()
				}
			},
		)

		configDir := pool.GetNextAccountConfigDir()
		logger.LogAccountAssigned(configDir)
		pool.ReportRequestStart(configDir)
		streamStart := time.Now().UnixMilli()

		ctx := r.Context()
		result, err := agent.RunAgentStreamWithContext(cfg, ws.WorkspaceDir, cmdArgs, parseLine, ws.TempDir, configDir, ctx)

		latencyMs := time.Now().UnixMilli() - streamStart
		pool.ReportRequestEnd(configDir)

		if err == nil && isRateLimited(result.Stderr) {
			pool.ReportRateLimit(configDir, 60000)
		}

		if err != nil || (result.Code != 0 && ctx.Err() == nil) {
			pool.ReportRequestError(configDir, latencyMs)
			if err != nil {
				logger.LogAgentError(cfg.SessionsLogPath, method, pathname, remoteAddress, -1, err.Error())
			} else {
				logger.LogAgentError(cfg.SessionsLogPath, method, pathname, remoteAddress, result.Code, result.Stderr)
			}
		} else {
			pool.ReportRequestSuccess(configDir, latencyMs)
		}
		logger.LogAccountStats(cfg.Verbose, pool.GetAccountStats())
		return
	}

	configDir := pool.GetNextAccountConfigDir()
	logger.LogAccountAssigned(configDir)
	pool.ReportRequestStart(configDir)
	syncStart := time.Now().UnixMilli()

	out, err := agent.RunAgentSync(cfg, ws.WorkspaceDir, cmdArgs, ws.TempDir, configDir, r.Context())
	syncLatency := time.Now().UnixMilli() - syncStart
	pool.ReportRequestEnd(configDir)

	if err != nil {
		pool.ReportRequestError(configDir, syncLatency)
		logger.LogAccountStats(cfg.Verbose, pool.GetAccountStats())
		httputil.WriteJSON(w, 500, map[string]interface{}{
			"error": map[string]string{"message": err.Error(), "code": "cursor_cli_error"},
		}, nil)
		return
	}

	if isRateLimited(out.Stderr) {
		pool.ReportRateLimit(configDir, 60000)
	}

	if out.Code != 0 {
		pool.ReportRequestError(configDir, syncLatency)
		logger.LogAccountStats(cfg.Verbose, pool.GetAccountStats())
		errMsg := logger.LogAgentError(cfg.SessionsLogPath, method, pathname, remoteAddress, out.Code, out.Stderr)
		httputil.WriteJSON(w, 500, map[string]interface{}{
			"error": map[string]string{"message": errMsg, "code": "cursor_cli_error"},
		}, nil)
		return
	}

	pool.ReportRequestSuccess(configDir, syncLatency)
	content := trimSpace(out.Stdout)
	logger.LogTrafficResponse(cfg.Verbose, model, content, false)
	logger.LogAccountStats(cfg.Verbose, pool.GetAccountStats())

	httputil.WriteJSON(w, 200, map[string]interface{}{
		"id":      id,
		"object":  "chat.completion",
		"created": created,
		"model":   model,
		"choices": []map[string]interface{}{
			{
				"index":         0,
				"message":       map[string]string{"role": "assistant", "content": content},
				"finish_reason": "stop",
			},
		},
		"usage": map[string]int{"prompt_tokens": 0, "completion_tokens": 0, "total_tokens": 0},
	}, truncatedHeaders)
}

func trimSpace(s string) string {
	result := ""
	start := 0
	end := len(s)
	for start < end && (s[start] == ' ' || s[start] == '\t' || s[start] == '\n' || s[start] == '\r') {
		start++
	}
	for end > start && (s[end-1] == ' ' || s[end-1] == '\t' || s[end-1] == '\n' || s[end-1] == '\r') {
		end--
	}
	result = s[start:end]
	return result
}