// Package layercompositions owns durable Seedream layer-editor documents.
package layercompositions

import (
	"context"
	"errors"
	"fmt"
	"math"
	"strings"
	"time"

	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/assets"
)

var (
	ErrConflict      = errors.New("layer composition version conflict")
	ErrInvalid       = errors.New("invalid layer composition")
	ErrAssetNotFound = errors.New("layer composition asset not found")
)

type Box [4]float64

type Layer struct {
	ID              string  `json:"id"`
	AssetID         string  `json:"assetId"`
	Name            string  `json:"name"`
	Description     string  `json:"description,omitempty"`
	Visible         bool    `json:"visible"`
	Box             Box     `json:"box"`
	Rotation        float64 `json:"rotation"`
	Source          string  `json:"source"`
	EditJobID       string  `json:"editJobId,omitempty"`
	OriginalAssetID string  `json:"originalAssetId,omitempty"`
}

type Composition struct {
	JobID       string    `json:"jobId"`
	OwnerID     string    `json:"-"`
	BaseAssetID string    `json:"baseAssetId"`
	BaseVisible bool      `json:"baseVisible"`
	Layers      []Layer   `json:"layers"`
	Version     int64     `json:"version"`
	CreatedAt   time.Time `json:"createdAt"`
	UpdatedAt   time.Time `json:"updatedAt"`
}

type Repository interface {
	FindLayerComposition(context.Context, string, string) (Composition, bool, error)
	SaveLayerComposition(context.Context, Composition, int64) (Composition, error)
}

type AssetCatalog interface {
	GetOwner(context.Context, string, string) (assets.Asset, bool, error)
}

type Service struct {
	repository Repository
	assets     AssetCatalog
}

func NewService(repository Repository, catalog AssetCatalog) *Service {
	return &Service{repository: repository, assets: catalog}
}

func (service *Service) Get(ctx context.Context, ownerID, jobID string) (Composition, bool, error) {
	if strings.TrimSpace(ownerID) == "" || strings.TrimSpace(jobID) == "" {
		return Composition{}, false, fmt.Errorf("%w: ownerId and jobId are required", ErrInvalid)
	}
	return service.repository.FindLayerComposition(ctx, ownerID, jobID)
}

func (service *Service) Save(ctx context.Context, ownerID, jobID string, expectedVersion int64, document Composition) (Composition, error) {
	document.OwnerID = strings.TrimSpace(ownerID)
	document.JobID = strings.TrimSpace(jobID)
	document.Version = 0
	if expectedVersion < 0 {
		return Composition{}, fmt.Errorf("%w: version must not be negative", ErrInvalid)
	}
	if err := normalizeAndValidate(&document); err != nil {
		return Composition{}, err
	}
	assetIDs := []string{document.BaseAssetID}
	for _, layer := range document.Layers {
		assetIDs = append(assetIDs, layer.AssetID)
		if layer.OriginalAssetID != "" {
			assetIDs = append(assetIDs, layer.OriginalAssetID)
		}
	}
	seen := map[string]bool{}
	for _, assetID := range assetIDs {
		if seen[assetID] {
			continue
		}
		seen[assetID] = true
		asset, found, err := service.assets.GetOwner(ctx, document.OwnerID, assetID)
		if err != nil {
			return Composition{}, fmt.Errorf("load layer asset: %w", err)
		}
		if !found || (asset.Kind != assets.KindImage && asset.Kind != assets.KindReference && asset.Kind != assets.KindMask) {
			return Composition{}, fmt.Errorf("%w: %s", ErrAssetNotFound, assetID)
		}
	}
	return service.repository.SaveLayerComposition(ctx, document, expectedVersion)
}

func normalizeAndValidate(document *Composition) error {
	if document.OwnerID == "" || document.JobID == "" || strings.TrimSpace(document.BaseAssetID) == "" {
		return fmt.Errorf("%w: ownerId, jobId, and baseAssetId are required", ErrInvalid)
	}
	document.BaseAssetID = strings.TrimSpace(document.BaseAssetID)
	if len(document.Layers) > 100 {
		return fmt.Errorf("%w: at most 100 layers are supported", ErrInvalid)
	}
	if document.Layers == nil {
		document.Layers = []Layer{}
	}
	ids := map[string]bool{}
	for index := range document.Layers {
		layer := &document.Layers[index]
		layer.ID = strings.TrimSpace(layer.ID)
		layer.AssetID = strings.TrimSpace(layer.AssetID)
		layer.Name = strings.TrimSpace(layer.Name)
		layer.Description = strings.TrimSpace(layer.Description)
		layer.Source = strings.TrimSpace(layer.Source)
		layer.EditJobID = strings.TrimSpace(layer.EditJobID)
		layer.OriginalAssetID = strings.TrimSpace(layer.OriginalAssetID)
		if layer.ID == "" || layer.AssetID == "" || layer.Name == "" {
			return fmt.Errorf("%w: every layer requires id, assetId, and name", ErrInvalid)
		}
		if ids[layer.ID] {
			return fmt.Errorf("%w: duplicate layer id %s", ErrInvalid, layer.ID)
		}
		ids[layer.ID] = true
		if len([]rune(layer.Name)) > 120 || len([]rune(layer.Description)) > 500 {
			return fmt.Errorf("%w: layer text is too long", ErrInvalid)
		}
		if !validLayerSource(layer.Source) {
			return fmt.Errorf("%w: unsupported layer source %s", ErrInvalid, layer.Source)
		}
		if err := validateBox(layer.Box); err != nil {
			return fmt.Errorf("%w: layer %s: %v", ErrInvalid, layer.ID, err)
		}
		if math.IsNaN(layer.Rotation) || math.IsInf(layer.Rotation, 0) {
			return fmt.Errorf("%w: layer rotation must be finite", ErrInvalid)
		}
		layer.Rotation = normalizeRotation(layer.Rotation)
	}
	return nil
}

func validLayerSource(value string) bool {
	switch value {
	case "provider", "upload", "library", "seedream-edit":
		return true
	default:
		return false
	}
}

func validateBox(box Box) error {
	for _, value := range box {
		if math.IsNaN(value) || math.IsInf(value, 0) || value < 0 || value > 1000 {
			return errors.New("box coordinates must be finite values between 0 and 1000")
		}
	}
	if box[2]-box[0] < 1 || box[3]-box[1] < 1 {
		return errors.New("box must have a positive width and height")
	}
	return nil
}

func normalizeRotation(value float64) float64 {
	value = math.Mod(value, 360)
	if value > 180 {
		value -= 360
	}
	if value <= -180 {
		value += 360
	}
	return math.Round(value*1000) / 1000
}