package handlers

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"

	"github.com/go-chi/chi/v5"
)

// MaildirMessage represents an email read directly from Maildir
type MaildirMessage struct {
	UID         uint32   `json:"uid"`
	Subject     string   `json:"subject"`
	From        string   `json:"from"`
	To          []string `json:"to"`
	Date        string   `json:"date"`
	Body        string   `json:"body"`
	Preview     string   `json:"preview"`
	Read        bool     `json:"read"`
	Attachments int      `json:"attachments"`
}

// getMaildirPath returns the path to the Maildir for a user
func getMaildirPath(email string) string {
	// Try docker container path first (when running inside container)
	basePath := "/mail"
	if _, err := os.Stat(basePath); os.IsNotExist(err) {
		// Fallback to host path
		basePath = "/opt/mailu/mail"
		if _, err := os.Stat(basePath); os.IsNotExist(err) {
			// Try to find mail via docker volume
			basePath = "/var/lib/docker/volumes"
		}
	}
	return filepath.Join(basePath, email)
}

// parseMaildirFile parses a single mail file
func parseMaildirFile(path string) (*MaildirMessage, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}

	content := string(data)
	msg := &MaildirMessage{
		Read:        strings.Contains(filepath.Base(path), ",S=") || !strings.Contains(path, "/new/"),
		Attachments: 0,
	}

	// Parse headers
	lines := strings.Split(content, "\n")
	inBody := false
	var bodyLines []string

	for _, line := range lines {
		if !inBody {
			if line == "" {
				inBody = true
				continue
			}
			if strings.HasPrefix(line, "Subject: ") {
				msg.Subject = strings.TrimPrefix(line, "Subject: ")
			} else if strings.HasPrefix(line, "From: ") {
				msg.From = strings.TrimPrefix(line, "From: ")
			} else if strings.HasPrefix(line, "To: ") {
				msg.To = append(msg.To, strings.TrimPrefix(line, "To: "))
			} else if strings.HasPrefix(line, "Date: ") {
				msg.Date = strings.TrimPrefix(line, "Date: ")
			}
		} else {
			bodyLines = append(bodyLines, line)
		}
	}

	body := strings.Join(bodyLines, "\n")
	msg.Body = body
	msg.Preview = truncateString(stripHTML(body), 200)

	// Generate UID from filename
	filename := filepath.Base(path)
	msg.UID = hashString(filename)

	return msg, nil
}

// listMaildirMessages lists all messages in a Maildir
func listMaildirMessages(maildir string, limit int) ([]MaildirMessage, error) {
	var messages []MaildirMessage

	// Read cur/ and new/ directories
	for _, subdir := range []string{"cur", "new"} {
		path := filepath.Join(maildir, subdir)
		entries, err := os.ReadDir(path)
		if err != nil {
			continue // Directory may not exist
		}

		for _, entry := range entries {
			if entry.IsDir() {
				continue
			}

			msg, err := parseMaildirFile(filepath.Join(path, entry.Name()))
			if err != nil {
				continue
			}

			messages = append(messages, *msg)
		}
	}

	// Sort by date (newest first)
	sort.Slice(messages, func(i, j int) bool {
		return messages[i].Date > messages[j].Date
	})

	if limit > 0 && len(messages) > limit {
		messages = messages[:limit]
	}

	return messages, nil
}

// GetMailInboxDirect returns emails directly from Maildir
func GetMailInboxDirect(w http.ResponseWriter, r *http.Request) {
	// Get user from context or use default
	email := "erik@landvex.com" // TODO: Get from JWT context

	maildir := getMaildirPath(email)
	if _, err := os.Stat(maildir); os.IsNotExist(err) {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusServiceUnavailable)
		json.NewEncoder(w).Encode(map[string]interface{}{
			"ok":    false,
			"error": "Maildir not found for user: " + email,
		})
		return
	}

	limit := 50
	if l := r.URL.Query().Get("limit"); l != "" {
		if parsed, err := strconv.Atoi(l); err == nil && parsed > 0 {
			limit = parsed
		}
	}

	messages, err := listMaildirMessages(maildir, limit)
	if err != nil {
		http.Error(w, fmt.Sprintf(`{"error":"%s"}`, err.Error()), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"ok":       true,
		"messages": messages,
		"total":    len(messages),
	})
}

// GetMailMessageDirect returns a single email from Maildir
func GetMailMessageDirect(w http.ResponseWriter, r *http.Request) {
	uidStr := chi.URLParam(r, "uid")
	uid, err := strconv.ParseUint(uidStr, 10, 32)
	if err != nil {
		http.Error(w, `{"error":"invalid uid"}`, http.StatusBadRequest)
		return
	}

	email := "erik@landvex.com" // TODO: Get from JWT context
	maildir := getMaildirPath(email)

	// Search for message with matching UID
	for _, subdir := range []string{"cur", "new"} {
		path := filepath.Join(maildir, subdir)
		entries, err := os.ReadDir(path)
		if err != nil {
			continue
		}

		for _, entry := range entries {
			if entry.IsDir() {
				continue
			}

			filename := filepath.Join(path, entry.Name())
			if hashString(entry.Name()) == uint32(uid) {
				msg, err := parseMaildirFile(filename)
				if err != nil {
					http.Error(w, `{"error":"failed to read message"}`, http.StatusInternalServerError)
					return
				}

				w.Header().Set("Content-Type", "application/json")
				json.NewEncoder(w).Encode(map[string]interface{}{
					"ok":      true,
					"message": msg,
				})
				return
			}
		}
	}

	http.Error(w, `{"error":"message not found"}`, http.StatusNotFound)
}

// MarkMailAsReadDirect marks a message as read
func MarkMailAsReadDirect(w http.ResponseWriter, r *http.Request) {
	uidStr := chi.URLParam(r, "uid")
	uid, err := strconv.ParseUint(uidStr, 10, 32)
	if err != nil {
		http.Error(w, `{"error":"invalid uid"}`, http.StatusBadRequest)
		return
	}

	email := "erik@landvex.com" // TODO: Get from JWT context
	maildir := getMaildirPath(email)

	// Move from new/ to cur/
	for _, entry := range []string{"new", "cur"} {
		path := filepath.Join(maildir, entry)
		entries, err := os.ReadDir(path)
		if err != nil {
			continue
		}

		for _, e := range entries {
			if e.IsDir() {
				continue
			}

			if hashString(e.Name()) == uint32(uid) {
				oldPath := filepath.Join(path, e.Name())
				newPath := filepath.Join(maildir, "cur", e.Name())

				if entry == "new" {
					if err := os.Rename(oldPath, newPath); err != nil {
						http.Error(w, `{"error":"failed to mark as read"}`, http.StatusInternalServerError)
						return
					}
				}

				w.Header().Set("Content-Type", "application/json")
				json.NewEncoder(w).Encode(map[string]interface{}{
					"ok": true,
				})
				return
			}
		}
	}

	http.Error(w, `{"error":"message not found"}`, http.StatusNotFound)
}

// Helper functions
func truncateString(s string, maxLen int) string {
	if len(s) <= maxLen {
		return s
	}
	return s[:maxLen] + "..."
}

func stripHTML(s string) string {
	// Simple HTML stripping
	result := strings.ReplaceAll(s, "<br>", "\n")
	result = strings.ReplaceAll(result, "<br/>", "\n")
	result = strings.ReplaceAll(result, "<p>", "\n")
	result = strings.ReplaceAll(result, "</p>", "")
	
	// Remove tags
	for {
		start := strings.Index(result, "<")
		if start == -1 {
			break
		}
		end := strings.Index(result[start:], ">")
		if end == -1 {
			break
		}
		result = result[:start] + result[start+end+1:]
	}
	
	return strings.TrimSpace(result)
}

func hashString(s string) uint32 {
	var h uint32 = 5381
	for i := 0; i < len(s); i++ {
		h = ((h << 5) + h) + uint32(s[i])
	}
	return h
}

// GetMailUnreadCountDirect returns unread count
func GetMailUnreadCountDirect(w http.ResponseWriter, r *http.Request) {
	email := "erik@landvex.com" // TODO: Get from JWT context
	maildir := getMaildirPath(email)

	count := 0
	newPath := filepath.Join(maildir, "new")
	entries, err := os.ReadDir(newPath)
	if err == nil {
		for _, e := range entries {
			if !e.IsDir() {
				count++
			}
		}
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"ok":    true,
		"count": count,
	})
}