package agent

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"github.com/openai/openai-go"
	oaioption "github.com/openai/openai-go/option"

	"llm-agent/prd"
)

const (
	baseURL    = "http://127.0.0.1:12434/v1"
	maxRetries = 3
	maxTurns   = 10
)

var systemPrompt = `Du bist ein autonomer Coding-Agent.
Erledige den gegebenen Task vollständig mit den bereitgestellten Tools.
Rufe task_complete auf sobald der Task erledigt ist.
Nutze ausschließlich relative Pfade.`

type AgentLoop struct {
	client  *openai.Client
	model   string
	workDir string
	prdFile string
	log     *Logger
}

func NewAgentLoop(model, workDir, prdFile string, verbose bool) *AgentLoop {
	client := openai.NewClient(
		oaioption.WithBaseURL(baseURL),
		oaioption.WithAPIKey("ollama"),
	)
	return &AgentLoop{
		client:  &client,
		model:   model,
		workDir: workDir,
		prdFile: prdFile,
		log:     NewLogger(verbose),
	}
}

func (a *AgentLoop) Run() error {
	tasks, err := prd.ParseTasks(a.prdFile)
	if err != nil {
		return fmt.Errorf("PRD lesen fehlgeschlagen: %w", err)
	}

	pending := 0
	for _, t := range tasks {
		if !t.Completed {
			pending++
		}
	}
	a.log.Info("📋 %d Tasks gefunden, %d offen", len(tasks), pending)

	for _, task := range tasks {
		if task.Completed {
			a.log.Info("✅ Überspringe (bereits erledigt): %s", task.Title)
			continue
		}

		a.log.TaskStart(task.Title)

		success := false
		var lastErr error
		for attempt := 1; attempt <= maxRetries; attempt++ {
			if attempt > 1 {
				a.log.Info("🔁 Retry %d/%d...", attempt, maxRetries)
				time.Sleep(time.Duration(attempt) * 2 * time.Second)
			}

			if err := a.runTask(task); err == nil {
				success = true
				break
			} else {
				lastErr = err
				a.log.Info("⚠️  Fehler: %v", err)
			}
		}

		if success {
			prd.MarkTaskComplete(a.prdFile, task.Title)
			a.log.TaskDone(task.Title)
		} else {
			a.log.TaskFailed(task.Title, maxRetries)
			_ = lastErr
		}
	}

	a.log.Info("\n🎉 Alle Tasks abgearbeitet!")
	return nil
}

func (a *AgentLoop) runTask(task prd.Task) error {
	executor := NewToolExecutor(a.workDir)

	messages := []openai.ChatCompletionMessageParamUnion{
		openai.SystemMessage(systemPrompt),
		openai.UserMessage(fmt.Sprintf(
			"Task: %s\nArbeitsverzeichnis: %s",
			task.Title, a.workDir,
		)),
	}

	a.log.ChatMessage("system", systemPrompt)
	a.log.ChatMessage("user", fmt.Sprintf(
		"Task: %s\nArbeitsverzeichnis: %s",
		task.Title, a.workDir,
	))

	for turn := 0; turn < maxTurns; turn++ {
		a.log.Turn(turn + 1)

		totalChars := 0
		for _, m := range messages {
			totalChars += len(fmt.Sprintf("%v", m))
		}

		start := time.Now()
		a.log.Debug("MODEL REQUEST: model=%s ~%d Zeichen\n%s",
			a.model, totalChars, formatMessages(messages))

		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
		resp, err := a.client.Chat.Completions.New(
			ctx,
			openai.ChatCompletionNewParams{
				Model:    a.model,
				Messages: messages,
				Tools:    Tools,
			},
		)
		cancel()

		elapsed := time.Since(start)
		if resp != nil && len(resp.Choices) > 0 {
			a.log.Debug("MODEL RESPONSE\n%s", formatResponse(resp, elapsed))
		}
		if err != nil {
			return fmt.Errorf("API-Fehler (~%d Zeichen): %w", totalChars, err)
		}

		choice := resp.Choices[0]
		messages = append(messages, choice.Message.ToParam())

		// Echte Tool-Calls vom SDK
		toolCalls := choice.Message.ToolCalls

		// Fallback: XML-Format parsen wenn Modell kein natives Tool Calling nutzt
		if len(toolCalls) == 0 && strings.Contains(choice.Message.Content, "<function=") {
			a.log.Debug("XML-Fallback: Parse Tool-Calls aus Content")
			toolCalls = parseXMLToolCalls(choice.Message.Content)
		}

		// Kein Tool-Call → LLM hat nur Text geantwortet
		if len(toolCalls) == 0 {
			a.log.ChatMessage("assistant", choice.Message.Content)
			nudge := "Nutze die bereitgestellten Tools. Rufe task_complete auf wenn du fertig bist."
			a.log.ChatMessage("user", nudge)
			messages = append(messages, openai.UserMessage(nudge))
			continue
		}

		// Tool-Calls ausführen
		for _, toolCall := range toolCalls {
			a.log.Info("  🔧 %s(%s)",
				toolCall.Function.Name,
				truncate(toolCall.Function.Arguments, 80),
			)

			result, done := executor.Execute(toolCall)
			a.log.ChatMessage("tool",
				fmt.Sprintf("%s → %s", toolCall.Function.Name, result))

			// Tool-Ergebnis zurück ans LLM
			messages = append(messages, openai.ToolMessage(result, toolCall.ID))

			if done {
				return nil // task_complete → Erfolg
			}
		}
	}

	return fmt.Errorf("maximale Turns (%d) erreicht", maxTurns)
}

// ─── XML Fallback Parser ──────────────────────────────────

// parseXMLToolCalls parst Tool-Calls im XML-Format das manche Modelle nutzen:
//
//	<function=write_file>
//	<parameter=path>hello.go</parameter>
//	<parameter=content>package main...</parameter>
//	</function>
func parseXMLToolCalls(content string) []openai.ChatCompletionMessageToolCall {
	var calls []openai.ChatCompletionMessageToolCall
	remaining := content
	callID := 0

	for {
		// Funktionsname extrahieren
		start := strings.Index(remaining, "<function=")
		if start == -1 {
			break
		}
		nameStart := start + len("<function=")
		nameEnd := strings.Index(remaining[nameStart:], ">")
		if nameEnd == -1 {
			break
		}
		funcName := strings.TrimSpace(remaining[nameStart : nameStart+nameEnd])

		// Block bis </function> extrahieren
		blockEnd := strings.Index(remaining, "</function>")
		if blockEnd == -1 {
			break
		}
		block := remaining[start : blockEnd+len("</function>")]

		// Parameter extrahieren und als JSON serialisieren
		params := extractXMLParams(block)
		argsJSON, err := json.Marshal(params)
		if err != nil {
			remaining = remaining[blockEnd+len("</function>"):]
			continue
		}

		callID++
		calls = append(calls, openai.ChatCompletionMessageToolCall{
			ID:   fmt.Sprintf("xml-call-%d", callID),
			Type: "function",
			Function: openai.ChatCompletionMessageToolCallFunction{
				Name:      funcName,
				Arguments: string(argsJSON),
			},
		})

		remaining = remaining[blockEnd+len("</function>"):]
	}

	return calls
}

// extractXMLParams extrahiert alle <parameter=key>value</parameter> aus einem Block
func extractXMLParams(block string) map[string]string {
	params := make(map[string]string)
	remaining := block

	for {
		start := strings.Index(remaining, "<parameter=")
		if start == -1 {
			break
		}

		// Key extrahieren
		keyStart := start + len("<parameter=")
		keyEnd := strings.Index(remaining[keyStart:], ">")
		if keyEnd == -1 {
			break
		}
		key := strings.TrimSpace(remaining[keyStart : keyStart+keyEnd])

		// Value extrahieren
		valueStart := keyStart + keyEnd + 1
		closeTag := "</parameter>"
		valueEnd := strings.Index(remaining[valueStart:], closeTag)
		if valueEnd == -1 {
			break
		}
		value := strings.TrimSpace(remaining[valueStart : valueStart+valueEnd])

		params[key] = value
		remaining = remaining[valueStart+valueEnd+len(closeTag):]
	}

	return params
}

// ─── Hilfsfunktionen ─────────────────────────────────────

func truncate(s string, max int) string {
	if len(s) <= max {
		return s
	}
	return s[:max] + "..."
}

func formatMessages(messages []openai.ChatCompletionMessageParamUnion) string {
	var sb strings.Builder
	for i, m := range messages {
		var role, content string
		switch {
		case m.OfSystem != nil:
			role = "system"
			content = m.OfSystem.Content.OfString.Value
		case m.OfUser != nil:
			role = "user"
			content = m.OfUser.Content.OfString.Value
		case m.OfAssistant != nil:
			role = "assistant"
			content = m.OfAssistant.Content.OfString.Value
		default:
			role = "other"
		}
		preview := strings.ReplaceAll(truncate(content, 120), "\n", "↵")
		sb.WriteString(fmt.Sprintf("  [%d] %-10s : %s\n", i, role, preview))
	}
	return sb.String()
}

func formatResponse(resp *openai.ChatCompletion, elapsed time.Duration) string {
	var sb strings.Builder
	sb.WriteString(fmt.Sprintf("  ID           : %s\n", resp.ID))
	sb.WriteString(fmt.Sprintf("  Modell        : %s\n", resp.Model))
	sb.WriteString(fmt.Sprintf("  Elapsed       : %s\n", elapsed.Round(time.Millisecond)))
	sb.WriteString(fmt.Sprintf("  Finish-Reason : %s\n", resp.Choices[0].FinishReason))
	sb.WriteString(fmt.Sprintf("  Tokens        : prompt=%d completion=%d total=%d\n",
		resp.Usage.PromptTokens,
		resp.Usage.CompletionTokens,
		resp.Usage.TotalTokens,
	))

	if len(resp.Choices[0].Message.ToolCalls) > 0 {
		sb.WriteString("  Tool-Calls    :\n")
		for _, tc := range resp.Choices[0].Message.ToolCalls {
			sb.WriteString(fmt.Sprintf("    → %s(%s)\n",
				tc.Function.Name,
				truncate(tc.Function.Arguments, 100),
			))
		}
	} else if content := resp.Choices[0].Message.Content; content != "" {
		sb.WriteString("  Content       :\n")
		for _, line := range strings.Split(content, "\n") {
			sb.WriteString(fmt.Sprintf("    %s\n", line))
		}
	}

	return sb.String()
}