package api

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"net/http"
	"strings"
	"sync"

	"github.com/archivmail/internal/index"
	"github.com/archivmail/pkg/mailparser"
)

// UploadJob tracks the progress of an EML/MBOX import job.
type UploadJob struct {
	mu       sync.Mutex
	ID       string `json:"id"`
	Status   string `json:"status"` // "running" | "done" | "error"
	Total    int    `json:"total"`
	Imported int    `json:"imported"`
	Skipped  int    `json:"skipped"`
	Errors   int    `json:"errors"`
	ErrMsg   string `json:"error_msg,omitempty"`
}

func (j *UploadJob) snapshot() uploadJobSnapshot {
	j.mu.Lock()
	defer j.mu.Unlock()
	return uploadJobSnapshot{
		ID:       j.ID,
		Status:   j.Status,
		Total:    j.Total,
		Imported: j.Imported,
		Skipped:  j.Skipped,
		Errors:   j.Errors,
		ErrMsg:   j.ErrMsg,
	}
}

type uploadJobSnapshot struct {
	ID       string `json:"id"`
	Status   string `json:"status"`
	Total    int    `json:"total"`
	Imported int    `json:"imported"`
	Skipped  int    `json:"skipped"`
	Errors   int    `json:"errors"`
	ErrMsg   string `json:"error_msg,omitempty"`
}

// handleUpload accepts a multipart upload of one or more .eml or .mbox files,
// starts a background import job and returns its ID immediately.
func (s *Server) handleUpload(w http.ResponseWriter, r *http.Request) {
	// 512 MB max total upload
	if err := r.ParseMultipartForm(512 << 20); err != nil {
		writeError(w, http.StatusBadRequest, "multipart parse failed: "+err.Error())
		return
	}

	files := r.MultipartForm.File["files"]
	if len(files) == 0 {
		writeError(w, http.StatusBadRequest, "no files uploaded")
		return
	}

	// Collect all raw messages from uploaded files
	type rawEntry struct {
		data   []byte
		isMbox bool
	}
	var entries []rawEntry

	for _, fh := range files {
		f, err := fh.Open()
		if err != nil {
			continue
		}
		buf := make([]byte, fh.Size)
		f.Read(buf) //nolint
		f.Close()

		name := strings.ToLower(fh.Filename)
		isMbox := strings.HasSuffix(name, ".mbox")
		entries = append(entries, rawEntry{buf, isMbox})
	}

	if len(entries) == 0 {
		writeError(w, http.StatusBadRequest, "no readable files")
		return
	}

	// Count total messages upfront
	var allMessages [][]byte
	for _, e := range entries {
		if e.isMbox {
			msgs := mailparser.SplitMbox(e.data)
			allMessages = append(allMessages, msgs...)
		} else {
			allMessages = append(allMessages, e.data)
		}
	}

	jobID := newJobID()
	job := &UploadJob{
		ID:     jobID,
		Status: "running",
		Total:  len(allMessages),
	}
	s.uploadJobs.Store(jobID, job)

	// Run import in background
	go s.runUploadJob(job, allMessages)

	writeJSON(w, http.StatusAccepted, map[string]string{"job_id": jobID})
}

// handleUploadProgress returns the current status of an upload job.
func (s *Server) handleUploadProgress(w http.ResponseWriter, r *http.Request) {
	jobID := r.PathValue("jobID")
	val, ok := s.uploadJobs.Load(jobID)
	if !ok {
		writeError(w, http.StatusNotFound, "job not found")
		return
	}
	job := val.(*UploadJob)
	writeJSON(w, http.StatusOK, job.snapshot())
}

func (s *Server) runUploadJob(job *UploadJob, messages [][]byte) {
	ctx := context.Background()

	for _, raw := range messages {
		result := s.importRawMessage(ctx, raw)
		job.mu.Lock()
		switch result {
		case "imported":
			job.Imported++
		case "skipped":
			job.Skipped++
		default:
			job.Errors++
		}
		job.mu.Unlock()
	}

	job.mu.Lock()
	job.Status = "done"
	job.mu.Unlock()
}

// importRawMessage stores and indexes a single raw message.
// Returns "imported", "skipped", or "error".
func (s *Server) importRawMessage(ctx context.Context, raw []byte) string {
	pm, err := mailparser.Parse(raw)
	if err != nil {
		s.logger.Warn("upload: parse failed", "err", err)
		return "error"
	}

	id, err := s.store.Save(raw, pm.Date)
	if err != nil {
		s.logger.Warn("upload: save failed", "err", err)
		return "error"
	}

	// Check dedup: storage.Save returns same id for duplicate content.
	// If already indexed, skip indexing.
	if already, _ := s.store.IsIndexed(ctx, id); already {
		return "skipped"
	}

	var attachNames []string
	for _, a := range pm.Attachments {
		if a.Filename != "" {
			attachNames = append(attachNames, a.Filename)
		}
	}

	doc := index.MailDocument{
		ID:            id,
		From:          pm.From,
		To:            strings.Join(pm.To, " "),
		Subject:       pm.Subject,
		Body:          pm.TextBody + " " + pm.HTMLBody,
		AttachNames:   strings.Join(attachNames, " "),
		HasAttachment: len(pm.Attachments) > 0,
		Date:          pm.Date,
		Size:          int64(len(raw)),
	}

	if err := s.idx.IndexSync(doc); err != nil {
		s.logger.Warn("upload: index failed", "id", id, "err", err)
		return "error"
	}

	if err := s.store.SetIndexedAt(ctx, id); err != nil {
		s.logger.Warn("upload: set indexed_at failed", "id", id, "err", err)
	}

	if err := s.store.SaveMeta(ctx, id, pm, len(raw)); err != nil {
		s.logger.Warn("upload: save meta failed", "id", id, "err", err)
	}

	return "imported"
}

func newJobID() string {
	b := make([]byte, 8)
	rand.Read(b) //nolint
	return hex.EncodeToString(b)
}