package main

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"

	"field-sync-gui/internal/config"
	"field-sync-gui/internal/copier"
	"field-sync-gui/internal/detect"
	"field-sync-gui/internal/manifest"

	"github.com/wailsapp/wails/v2/pkg/runtime"
)

// SlotState holds per-slot progress
type SlotState struct {
	Slot       string  `json:"slot"`
	Mountpoint string  `json:"mountpoint"`
	Label      string  `json:"label"`
	Status     string  `json:"status"` // idle|scanning|copying|uploading|done|error
	FilesTotal int     `json:"filesTotal"`
	FilesDone  int     `json:"filesDone"`
	BytesTotal int64   `json:"bytesTotal"`
	BytesDone  int64   `json:"bytesDone"`
	SpeedMBs   float64 `json:"speedMBs"`
	Error      string  `json:"error,omitempty"`
}

// Snapshot is the full UI state
type Snapshot struct {
	SessionID string       `json:"sessionID"`
	Slots     [4]SlotState `json:"slots"`
	Running   bool         `json:"running"`
	DryRun    bool         `json:"dryRun"`
	Config    config.Config `json:"config"`
}

// SlotPayload is the per-slot input from the frontend
type SlotPayload struct {
	Slot       string `json:"slot"`
	Mountpoint string `json:"mountpoint"`
}

// App is the Wails application struct
type App struct {
	ctx       context.Context
	cfg       config.Config
	sessionID string
	slots     [4]SlotState
	mu        sync.RWMutex
	cancel    context.CancelFunc
	dryRun    bool
	manifest  *manifest.Manifest
	running   bool
}

// NewApp creates a new App
func NewApp() *App {
	return &App{}
}

// startup is called by Wails when the app starts
func (a *App) startup(ctx context.Context) {
	a.ctx = ctx
	a.cfg = config.Load(".env")
	for i, letter := range []string{"A", "B", "C", "D"} {
		a.slots[i] = SlotState{Slot: letter, Status: "idle"}
	}
}

// ScanCards returns up to 4 detected SD cards
func (a *App) ScanCards() []detect.SDCard {
	cards := detect.Detect()
	if len(cards) > 4 {
		cards = cards[:4]
	}
	return cards
}

// LoadConfig returns current config
func (a *App) LoadConfig() config.Config {
	return a.cfg
}

// SetDryRun toggles dry-run mode
func (a *App) SetDryRun(b bool) {
	a.mu.Lock()
	a.dryRun = b
	a.mu.Unlock()
}

// GetSnapshot returns current state
func (a *App) GetSnapshot() Snapshot {
	a.mu.RLock()
	defer a.mu.RUnlock()
	return Snapshot{
		SessionID: a.sessionID,
		Slots:     a.slots,
		Running:   a.running,
		DryRun:    a.dryRun,
		Config:    a.cfg,
	}
}

// CancelIngest cancels a running ingest
func (a *App) CancelIngest() error {
	a.mu.Lock()
	defer a.mu.Unlock()
	if a.cancel != nil {
		a.cancel()
	}
	return nil
}

// StartIngest launches the ingest pipeline in a goroutine
func (a *App) StartIngest(slotConfigs []SlotPayload) error {
	a.mu.Lock()
	if a.running {
		a.mu.Unlock()
		return fmt.Errorf("ingest already running")
	}

	// Generate session ID
	now := time.Now()
	a.sessionID = fmt.Sprintf("cosma-%s", now.Format("20060102-1504"))
	a.manifest = manifest.New(a.sessionID)
	a.running = true

	ctx, cancel := context.WithCancel(a.ctx)
	a.cancel = cancel

	dryRun := a.dryRun
	cfg := a.cfg
	sessionID := a.sessionID

	// Reset slots
	for i := range a.slots {
		a.slots[i].Status = "idle"
		a.slots[i].FilesTotal = 0
		a.slots[i].FilesDone = 0
		a.slots[i].BytesTotal = 0
		a.slots[i].BytesDone = 0
		a.slots[i].SpeedMBs = 0
		a.slots[i].Error = ""
	}
	a.mu.Unlock()

	go func() {
		defer func() {
			a.mu.Lock()
			a.running = false
			a.cancel = nil
			a.mu.Unlock()
			runtime.EventsEmit(a.ctx, "session-done", a.GetSnapshot())
		}()

		// Map slot letter → index
		slotIndex := map[string]int{"A": 0, "B": 1, "C": 2, "D": 3}

		// Build all jobs per slot
		type slotJobs struct {
			idx  int
			cfg  SlotPayload
			jobs []copier.FileJob
		}

		var allSlots []slotJobs
		for _, sc := range slotConfigs {
			idx, ok := slotIndex[sc.Slot]
			if !ok {
				continue
			}

			a.mu.Lock()
			a.slots[idx].Slot = sc.Slot
			a.slots[idx].Mountpoint = sc.Mountpoint
			a.slots[idx].Label = filepath.Base(sc.Mountpoint)
			a.slots[idx].Status = "scanning"
			a.mu.Unlock()
			runtime.EventsEmit(a.ctx, "slot-update", a.slots[idx])

			var jobs []copier.FileJob
			var bytesTotal int64
			_ = filepath.Walk(sc.Mountpoint, func(path string, info os.FileInfo, err error) error {
				if err != nil || info.IsDir() {
					return nil
				}
				if !detect.HasMediaExtension(path) {
					return nil
				}
				rel, _ := filepath.Rel(sc.Mountpoint, path)
				label := filepath.Base(sc.Mountpoint)
				localDest := filepath.Join(cfg.LocalDest, sessionID, label, rel)
				s3Key := fmt.Sprintf("%s/%s/%s", sessionID, label, rel)
				jobs = append(jobs, copier.FileJob{
					Source:     path,
					LocalDest:  localDest,
					S3Bucket:   cfg.S3Bucket,
					S3Key:      s3Key,
					AWSProfile: cfg.AWSProfile,
				})
				bytesTotal += info.Size()
				return nil
			})

			a.mu.Lock()
			a.slots[idx].FilesTotal = len(jobs)
			a.slots[idx].BytesTotal = bytesTotal
			a.slots[idx].Status = "copying"
			a.mu.Unlock()
			runtime.EventsEmit(a.ctx, "slot-update", a.slots[idx])

			allSlots = append(allSlots, slotJobs{idx: idx, cfg: sc, jobs: jobs})
		}

		// Dry-run: mark all done immediately
		if dryRun {
			for _, sl := range allSlots {
				for _, job := range sl.jobs {
					a.manifest.Append(manifest.Entry{
						Source:    job.Source,
						LocalDest: job.LocalDest,
						S3Path:    fmt.Sprintf("s3://%s/%s", job.S3Bucket, job.S3Key),
						Status:    "dry-run",
					})
				}
				a.mu.Lock()
				a.slots[sl.idx].FilesDone = a.slots[sl.idx].FilesTotal
				a.slots[sl.idx].BytesDone = a.slots[sl.idx].BytesTotal
				a.slots[sl.idx].Status = "done"
				snap := a.slots[sl.idx]
				a.mu.Unlock()
				runtime.EventsEmit(a.ctx, "slot-update", snap)
			}
			_ = a.manifest.Save(filepath.Join(cfg.LocalDest, sessionID, "manifest.json"))
			return
		}

		// Real copy: flatten all jobs into channel, track per-slot
		jobCh := make(chan copier.FileJob, 64)

		// Build slot index from job source
		jobSlot := make(map[string]int)
		for _, sl := range allSlots {
			for _, j := range sl.jobs {
				jobSlot[j.Source] = sl.idx
			}
		}

		mani := a.manifest

		pool := &copier.Pool{
			Workers: cfg.Concurrency,
			OnResult: func(res copier.FileResult) {
				idx, ok := jobSlot[res.Job.Source]
				if !ok {
					return
				}
				status := "done"
				errStr := ""
				if res.Error != nil {
					status = "error"
					errStr = res.Error.Error()
				}
				mani.Append(manifest.Entry{
					Source:    res.Job.Source,
					LocalDest: res.Job.LocalDest,
					S3Path:    fmt.Sprintf("s3://%s/%s", res.Job.S3Bucket, res.Job.S3Key),
					SHA256:    res.SHA256,
					Bytes:     res.Bytes,
					Status:    status,
					Error:     errStr,
				})

				a.mu.Lock()
				a.slots[idx].FilesDone++
				a.slots[idx].BytesDone += res.Bytes
				if res.Error != nil {
					a.slots[idx].Error = errStr
					a.slots[idx].Status = "error"
				} else if a.slots[idx].FilesDone >= a.slots[idx].FilesTotal {
					a.slots[idx].Status = "done"
				}
				snap := a.slots[idx]
				a.mu.Unlock()
				runtime.EventsEmit(a.ctx, "slot-update", snap)
			},
		}

		go func() {
			for _, sl := range allSlots {
				for _, j := range sl.jobs {
					select {
					case <-ctx.Done():
						close(jobCh)
						return
					case jobCh <- j:
					}
				}
			}
			close(jobCh)
		}()

		pool.Run(ctx, jobCh)
		_ = mani.Save(filepath.Join(cfg.LocalDest, sessionID, "manifest.json"))
	}()

	return nil
}