package jobs

import (
	"context"
	"errors"
	"fmt"
	"sync"
	"time"

	"git.apinb.com/bsm-sdk/core/logger"
	"git.apinb.com/ops/files/internal/config"
	"git.apinb.com/ops/files/internal/impl"
	"git.apinb.com/ops/files/internal/models"
	"git.apinb.com/ops/files/internal/storage"
)

type IntegrityStatus struct {
	Running      bool      `json:"running"`
	LastStarted  time.Time `json:"last_started,omitempty"`
	LastSuccess  time.Time `json:"last_success,omitempty"`
	LastError    string    `json:"last_error,omitempty"`
	Checked      int64     `json:"checked"`
	Missing      int64     `json:"missing"`
	SizeMismatch int64     `json:"size_mismatch"`
	ETagMismatch int64     `json:"etag_mismatch"`
}

var integrityRuntime struct {
	sync.RWMutex
	IntegrityStatus
	wg sync.WaitGroup
}

func StartIntegrity(ctx context.Context) error {
	integrityRuntime.Lock()
	if integrityRuntime.Running {
		integrityRuntime.Unlock()
		return fmt.Errorf("文件完整性任务已启动")
	}
	integrityRuntime.Unlock()
	if err := runIntegrity(ctx); err != nil {
		return fmt.Errorf("首次核对文件完整性失败: %w", err)
	}
	integrityRuntime.Lock()
	integrityRuntime.Running = true
	integrityRuntime.Unlock()
	integrityRuntime.wg.Add(1)
	go func() {
		defer integrityRuntime.wg.Done()
		defer func() {
			integrityRuntime.Lock()
			integrityRuntime.Running = false
			integrityRuntime.Unlock()
		}()
		ticker := time.NewTicker(time.Duration(config.Spec.Cleanup.IntegrityIntervalSeconds) * time.Second)
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				if err := runIntegrity(ctx); err != nil && !errors.Is(err, context.Canceled) {
					logger.Errorf("stage=files_integrity error=%v", err)
				}
			}
		}
	}()
	return nil
}

func IntegrityStatusSnapshot() IntegrityStatus {
	integrityRuntime.RLock()
	defer integrityRuntime.RUnlock()
	return integrityRuntime.IntegrityStatus
}

func waitIntegrity(ctx context.Context) error {
	done := make(chan struct{})
	go func() {
		integrityRuntime.wg.Wait()
		close(done)
	}()
	select {
	case <-done:
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}

func runIntegrity(ctx context.Context) error {
	startedAt := time.Now().UTC()
	status := IntegrityStatus{Running: true, LastStarted: startedAt}
	integrityRuntime.Lock()
	status.LastSuccess = integrityRuntime.LastSuccess
	integrityRuntime.IntegrityStatus = status
	integrityRuntime.Unlock()

	var lastID uint
	for {
		var fileObjects []models.FileObject
		result := impl.DBService.WithContext(ctx).
			Where("status = ? AND id > ?", models.FileStatusReady, lastID).
			Order("id ASC").Limit(config.Spec.Cleanup.IntegrityBatchSize).Find(&fileObjects)
		if result.Error != nil {
			return finishIntegrity(status, result.Error)
		}
		if len(fileObjects) == 0 {
			break
		}
		for _, fileObject := range fileObjects {
			if err := ctx.Err(); err != nil {
				return finishIntegrity(status, err)
			}
			status.Checked++
			objectInfo, err := impl.StorageService.Stat(ctx, fileObject.ObjectKey)
			if err != nil {
				if errors.Is(err, storage.ErrObjectNotFound) {
					status.Missing++
					continue
				}
				return finishIntegrity(status, err)
			}
			if objectInfo.Size != fileObject.ActualSize {
				status.SizeMismatch++
			}
			if objectInfo.StorageETag != fileObject.StorageETag {
				status.ETagMismatch++
			}
		}
		lastID = fileObjects[len(fileObjects)-1].ID
		if len(fileObjects) < config.Spec.Cleanup.IntegrityBatchSize {
			break
		}
	}
	status.LastSuccess = time.Now().UTC()
	status.Running = integrityRuntime.Running
	integrityRuntime.Lock()
	integrityRuntime.IntegrityStatus = status
	integrityRuntime.Unlock()
	return nil
}

func finishIntegrity(status IntegrityStatus, err error) error {
	status.LastError = err.Error()
	status.Running = integrityRuntime.Running
	integrityRuntime.Lock()
	integrityRuntime.IntegrityStatus = status
	integrityRuntime.Unlock()
	return err
}