package services

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"math"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"go.etcd.io/bbolt"
)

var storageSpeedTestsBucket = []byte("storage_speed_tests")

const (
	StorageSpeedModeSmall  = "small"
	StorageSpeedModeBig    = "big"
	StorageSpeedModeMixed  = "mixed"
	StorageSpeedModeCustom = "custom"

	StorageSpeedStatusRunning = "running"
	StorageSpeedStatusDone    = "done"
	StorageSpeedStatusFailed  = "failed"
)

type StorageSpeedTest struct {
	ID               string    `json:"id"`
	BackendID        string    `json:"backendId"`
	BackendName      string    `json:"backendName"`
	Mode             string    `json:"mode"`
	Status           string    `json:"status"`
	Stage            string    `json:"stage"`
	ProgressPercent  int       `json:"progressPercent"`
	CustomFileCount  int       `json:"customFileCount,omitempty"`
	CustomFileSizeMB float64   `json:"customFileSizeMb,omitempty"`
	StartedAt        time.Time `json:"startedAt"`
	FinishedAt       time.Time `json:"finishedAt,omitempty"`
	BytesWritten     int64     `json:"bytesWritten"`
	BytesRead        int64     `json:"bytesRead"`
	FilesWritten     int       `json:"filesWritten"`
	WriteDurationMS  int64     `json:"writeDurationMs"`
	ReadDurationMS   int64     `json:"readDurationMs"`
	DeleteDurationMS int64     `json:"deleteDurationMs"`
	Error            string    `json:"error,omitempty"`
}

func (t StorageSpeedTest) ModeLabel() string {
	switch t.Mode {
	case StorageSpeedModeSmall:
		return "Many small files"
	case StorageSpeedModeBig:
		return "One big file"
	case StorageSpeedModeMixed:
		return "Average mix"
	case StorageSpeedModeCustom:
		return "Custom"
	default:
		return t.Mode
	}
}

func (t StorageSpeedTest) StartedLabel() string {
	if t.StartedAt.IsZero() {
		return ""
	}
	return t.StartedAt.Format("Jan 2, 15:04:05")
}

func (t StorageSpeedTest) FinishedLabel() string {
	if t.FinishedAt.IsZero() {
		return "Still running"
	}
	return t.FinishedAt.Format("Jan 2, 15:04:05")
}

func (t StorageSpeedTest) TotalSizeLabel() string {
	return FormatMegabytesFromBytes(max(t.BytesWritten, t.BytesRead))
}

func (t StorageSpeedTest) WriteSpeedLabel() string {
	return speedLabel(t.BytesWritten, t.WriteDurationMS)
}

func (t StorageSpeedTest) ReadSpeedLabel() string {
	return speedLabel(t.BytesRead, t.ReadDurationMS)
}

func speedLabel(bytes int64, durationMS int64) string {
	if bytes <= 0 || durationMS <= 0 {
		return "n/a"
	}
	mb := float64(bytes) / 1024 / 1024
	seconds := float64(durationMS) / 1000
	value := math.Round((mb/seconds)*100) / 100
	return fmt.Sprintf("%.2f MB/s", value)
}

func (s *StorageService) StartSpeedTest(backendID, mode string) (StorageSpeedTest, error) {
	return s.StartSpeedTestWithOptions(backendID, StorageSpeedTestOptions{Mode: mode})
}

type StorageSpeedTestOptions struct {
	Mode             string
	CustomFileCount  int
	CustomFileSizeMB float64
}

func (s *StorageService) StartSpeedTestWithOptions(backendID string, options StorageSpeedTestOptions) (StorageSpeedTest, error) {
	cfg, err := s.BackendConfig(backendID)
	if err != nil {
		return StorageSpeedTest{}, err
	}
	if !cfg.Enabled {
		return StorageSpeedTest{}, fmt.Errorf("storage backend is disabled")
	}
	if !cfg.LastTestSuccess {
		return StorageSpeedTest{}, fmt.Errorf("run a successful connection test before testing speed")
	}
	mode := normalizeSpeedTestMode(options.Mode)
	if mode == StorageSpeedModeCustom {
		if err := validateCustomSpeedTest(options.CustomFileCount, options.CustomFileSizeMB); err != nil {
			return StorageSpeedTest{}, err
		}
	}
	test := StorageSpeedTest{
		ID:               randomID(10),
		BackendID:        cfg.ID,
		BackendName:      cfg.Name,
		Mode:             mode,
		Status:           StorageSpeedStatusRunning,
		Stage:            "queued",
		CustomFileCount:  options.CustomFileCount,
		CustomFileSizeMB: options.CustomFileSizeMB,
		StartedAt:        time.Now().UTC(),
	}
	if err := s.saveSpeedTest(test); err != nil {
		return StorageSpeedTest{}, err
	}
	return test, nil
}

func (s *StorageService) RunSpeedTest(ctx context.Context, testID string) {
	test, err := s.speedTest(testID)
	if err != nil {
		return
	}
	if err := s.runSpeedTest(ctx, &test); err != nil {
		test.Status = StorageSpeedStatusFailed
		test.Error = err.Error()
		test.FinishedAt = time.Now().UTC()
		if test.Stage == "" || test.Stage == "queued" {
			test.Stage = "failed"
		}
		_ = s.saveSpeedTest(test)
		return
	}
	test.Status = StorageSpeedStatusDone
	test.Stage = "complete"
	test.ProgressPercent = 100
	test.FinishedAt = time.Now().UTC()
	_ = s.saveSpeedTest(test)
}

func (s *StorageService) ListSpeedTests(backendID string, limit int) ([]StorageSpeedTest, error) {
	var tests []StorageSpeedTest
	err := s.db.View(func(tx *bbolt.Tx) error {
		bucket := tx.Bucket(storageSpeedTestsBucket)
		if bucket == nil {
			return nil
		}
		return bucket.ForEach(func(_, value []byte) error {
			var test StorageSpeedTest
			if err := json.Unmarshal(value, &test); err != nil {
				return err
			}
			if backendID == "" || test.BackendID == backendID {
				tests = append(tests, test)
			}
			return nil
		})
	})
	if err != nil {
		return nil, err
	}
	sort.Slice(tests, func(i, j int) bool {
		return tests[i].StartedAt.After(tests[j].StartedAt)
	})
	if limit > 0 && len(tests) > limit {
		tests = tests[:limit]
	}
	return tests, nil
}

func (s *StorageService) speedTest(id string) (StorageSpeedTest, error) {
	var test StorageSpeedTest
	err := s.db.View(func(tx *bbolt.Tx) error {
		data := tx.Bucket(storageSpeedTestsBucket).Get([]byte(id))
		if data == nil {
			return fmt.Errorf("speed test not found")
		}
		return json.Unmarshal(data, &test)
	})
	return test, err
}

func (s *StorageService) saveSpeedTest(test StorageSpeedTest) error {
	data, err := json.Marshal(test)
	if err != nil {
		return err
	}
	return s.db.Update(func(tx *bbolt.Tx) error {
		return tx.Bucket(storageSpeedTestsBucket).Put([]byte(test.ID), data)
	})
}

func (s *StorageService) runSpeedTest(ctx context.Context, test *StorageSpeedTest) error {
	backend, err := s.Backend(test.BackendID)
	if err != nil {
		return err
	}
	files, err := createSpeedTestFiles(test)
	if err != nil {
		return err
	}
	defer os.RemoveAll(files.Root)
	keys := make([]string, 0, len(files.Files))
	defer func() {
		for _, key := range keys {
			_ = backend.Delete(context.Background(), key)
		}
	}()

	writeStart := time.Now()
	for i, file := range files.Files {
		key := fmt.Sprintf(".warpbox-speed-test/%s/%03d.bin", test.ID, i)
		source, err := os.Open(file.Path)
		if err != nil {
			return err
		}
		err = backend.Put(ctx, key, source, file.Size, "application/octet-stream")
		source.Close()
		if err != nil {
			return err
		}
		keys = append(keys, key)
		test.BytesWritten += file.Size
		test.FilesWritten++
		updateSpeedProgress(test, "writing", i+1, len(files.Files), 0, 45)
		_ = s.saveSpeedTest(*test)
	}
	test.WriteDurationMS = time.Since(writeStart).Milliseconds()
	_ = s.saveSpeedTest(*test)

	readStart := time.Now()
	for i, key := range keys {
		object, err := backend.Get(ctx, key)
		if err != nil {
			return err
		}
		read, err := io.Copy(io.Discard, object.Body)
		object.Body.Close()
		if err != nil {
			return err
		}
		test.BytesRead += read
		updateSpeedProgress(test, "reading", i+1, len(keys), 45, 90)
		_ = s.saveSpeedTest(*test)
	}
	test.ReadDurationMS = time.Since(readStart).Milliseconds()
	_ = s.saveSpeedTest(*test)

	deleteStart := time.Now()
	for i, key := range keys {
		if err := backend.Delete(ctx, key); err != nil {
			return err
		}
		updateSpeedProgress(test, "cleaning up", i+1, len(keys), 90, 100)
		_ = s.saveSpeedTest(*test)
	}
	test.DeleteDurationMS = time.Since(deleteStart).Milliseconds()
	keys = nil
	return nil
}

func updateSpeedProgress(test *StorageSpeedTest, stage string, done, total, start, end int) {
	test.Stage = stage
	if total <= 0 {
		test.ProgressPercent = start
		return
	}
	span := end - start
	progress := start + int(math.Round(float64(span)*float64(done)/float64(total)))
	if progress < 0 {
		progress = 0
	}
	if progress > 100 {
		progress = 100
	}
	test.ProgressPercent = progress
}

type speedTestFile struct {
	Path string
	Size int64
}

type speedTestFiles struct {
	Root  string
	Files []speedTestFile
}

func createSpeedTestFiles(test *StorageSpeedTest) (speedTestFiles, error) {
	plan, err := speedTestPlan(test)
	if err != nil {
		return speedTestFiles{}, err
	}
	root, err := os.MkdirTemp("", "warpbox-speed-test-*")
	if err != nil {
		return speedTestFiles{}, err
	}
	files := speedTestFiles{Root: root, Files: make([]speedTestFile, 0, len(plan))}
	for i, size := range plan {
		path := filepath.Join(root, fmt.Sprintf("%03d.bin", i))
		if err := writeMockFile(path, size, byte(65+(i%23))); err != nil {
			os.RemoveAll(root)
			return speedTestFiles{}, err
		}
		files.Files = append(files.Files, speedTestFile{Path: path, Size: size})
	}
	return files, nil
}

func speedTestPlan(test *StorageSpeedTest) ([]int64, error) {
	mode := normalizeSpeedTestMode(test.Mode)
	if mode == StorageSpeedModeCustom {
		if err := validateCustomSpeedTest(test.CustomFileCount, test.CustomFileSizeMB); err != nil {
			return nil, err
		}
		size := MegabytesToBytes(test.CustomFileSizeMB)
		plan := make([]int64, test.CustomFileCount)
		for i := range plan {
			plan[i] = size
		}
		return plan, nil
	}
	return speedTestPlanForMode(mode), nil
}

func speedTestPlanForMode(mode string) []int64 {
	mode = normalizeSpeedTestMode(mode)
	switch mode {
	case StorageSpeedModeSmall:
		return repeatedSizes(24, 32*1024)
	case StorageSpeedModeBig:
		return repeatedSizes(1, 8*1024*1024)
	default:
		sizes := repeatedSizes(8, 64*1024)
		return append(sizes, repeatedSizes(1, 4*1024*1024)...)
	}
}

func repeatedSizes(count int, size int64) []int64 {
	sizes := make([]int64, 0, count)
	for i := 0; i < count; i++ {
		sizes = append(sizes, size)
	}
	return sizes
}

func writeMockFile(path string, size int64, seed byte) error {
	target, err := os.Create(path)
	if err != nil {
		return err
	}
	defer target.Close()
	chunk := make([]byte, 64*1024)
	for i := range chunk {
		chunk[i] = seed
	}
	remaining := size
	for remaining > 0 {
		writeSize := int64(len(chunk))
		if remaining < writeSize {
			writeSize = remaining
		}
		if _, err := target.Write(chunk[:int(writeSize)]); err != nil {
			return err
		}
		remaining -= writeSize
	}
	return nil
}

func validateCustomSpeedTest(count int, sizeMB float64) error {
	if count <= 0 || count > 500 {
		return fmt.Errorf("custom speed test file count must be between 1 and 500")
	}
	if sizeMB <= 0 {
		return fmt.Errorf("custom speed test file size must be positive")
	}
	totalMB := float64(count) * sizeMB
	if totalMB > 4096 {
		return fmt.Errorf("custom speed test total size cannot exceed 4096 MB")
	}
	return nil
}

func normalizeSpeedTestMode(mode string) string {
	switch strings.TrimSpace(mode) {
	case StorageSpeedModeSmall:
		return StorageSpeedModeSmall
	case StorageSpeedModeBig:
		return StorageSpeedModeBig
	case StorageSpeedModeCustom:
		return StorageSpeedModeCustom
	default:
		return StorageSpeedModeMixed
	}
}