package storage

import (
	"context"
	"errors"
	"io"
	"time"
)

var (
	ErrInsufficientSpace = errors.New("文件存储空间不足")
	ErrUploadLocked      = errors.New("文件正在上传")
	ErrObjectNotFound    = errors.New("文件对象不存在")
)

type UploadRequest struct {
	FileID       string
	ObjectKey    string
	ContentType  string
	ExpectedSize int64
	ExpiresAt    time.Time
}

type UploadInstruction struct {
	Method    string            `json:"method"`
	URL       string            `json:"url"`
	Headers   map[string]string `json:"headers"`
	ExpiresAt time.Time         `json:"expires_at"`
}

type ByteRange struct {
	Start int64
	End   int64
}

func (r ByteRange) Length() int64 {
	return r.End - r.Start + 1
}

type ObjectInfo struct {
	Size         int64
	StorageETag  string
	LastModified time.Time
}

type DiskStatus struct {
	Path             string  `json:"path"`
	TotalBytes       uint64  `json:"total_bytes"`
	UsedBytes        uint64  `json:"used_bytes"`
	FreeBytes        uint64  `json:"free_bytes"`
	UsedPercent      float64 `json:"used_percent"`
	MinimumFreeBytes uint64  `json:"minimum_free_bytes"`
	Level            string  `json:"level"`
}

type RuntimeStatus struct {
	Provider  string      `json:"provider"`
	Container string      `json:"container"`
	Writable  bool        `json:"writable"`
	Disk      *DiskStatus `json:"disk,omitempty"`
}

type Backend interface {
	Provider() string
	Container() string
	PrepareUpload(context.Context, UploadRequest) (UploadInstruction, error)
	Open(context.Context, string, *ByteRange) (io.ReadCloser, error)
	Stat(context.Context, string) (ObjectInfo, error)
	Delete(context.Context, string) error
	Status(context.Context) (RuntimeStatus, error)
}

type UploadReceiver interface {
	AcquireUpload(context.Context, string) (release func() error, err error)
	ReceiveUpload(context.Context, UploadRequest, io.Reader) (ObjectInfo, error)
	DiscardUpload(context.Context, string) error
}