package model

import (
	"fmt"
	"strings"
	"time"
	"unicode"

	"gorm.io/gorm"
)

// FileBlob represents a physical file stored in MinIO, deduplicated by SHA256.
type FileBlob struct {
	ID        int64     `gorm:"primaryKey;autoIncrement" json:"id"`
	SHA256    string    `gorm:"uniqueIndex;size:64;not null" json:"sha256"`
	MinioKey  string    `gorm:"size:255;not null" json:"minio_key"`
	FileSize  int64     `gorm:"not null" json:"file_size"`
	MimeType  string    `gorm:"size:255" json:"mime_type"`
	RefCount  int       `gorm:"not null;default:0" json:"ref_count"`
	CreatedAt time.Time `json:"created_at"`
	UpdatedAt time.Time `json:"updated_at"`
}

func (FileBlob) TableName() string {
	return "hpc_file_blobs"
}

// File represents a logical file visible to users, backed by a FileBlob.
type File struct {
	ID         int64          `gorm:"primaryKey;autoIncrement" json:"id"`
	Name       string         `gorm:"size:255;not null" json:"name"`
	FolderID   *int64         `gorm:"index" json:"folder_id,omitempty"`
	BlobSHA256 string         `gorm:"size:64;not null" json:"blob_sha256"`
	UserID     *int64         `gorm:"index" json:"user_id,omitempty"`
	CreatedAt  time.Time      `json:"created_at"`
	UpdatedAt  time.Time      `json:"updated_at"`
	DeletedAt  gorm.DeletedAt `gorm:"index" json:"deleted_at,omitempty"`
}

func (File) TableName() string {
	return "hpc_files"
}

// Folder represents a directory in the virtual file system.
type Folder struct {
	ID        int64          `gorm:"primaryKey;autoIncrement" json:"id"`
	Name      string         `gorm:"size:255;not null" json:"name"`
	ParentID  *int64         `gorm:"index" json:"parent_id,omitempty"`
	Path      string         `gorm:"uniqueIndex;size:768;not null" json:"path"`
	UserID    *int64         `gorm:"index" json:"user_id,omitempty"`
	CreatedAt time.Time      `json:"created_at"`
	UpdatedAt time.Time      `json:"updated_at"`
	DeletedAt gorm.DeletedAt `gorm:"index" json:"deleted_at,omitempty"`
}

func (Folder) TableName() string {
	return "hpc_folders"
}

// UploadSession represents an in-progress chunked upload.
// State transitions: pending→uploading, pending→completed(zero-byte), uploading→merging,
// uploading→cancelled, merging→completed, merging→failed, any→expired
type UploadSession struct {
	ID          int64     `gorm:"primaryKey;autoIncrement" json:"id"`
	FileName    string    `gorm:"size:255;not null" json:"file_name"`
	FileSize    int64     `gorm:"not null" json:"file_size"`
	ChunkSize   int64     `gorm:"not null" json:"chunk_size"`
	TotalChunks int       `gorm:"not null" json:"total_chunks"`
	SHA256      string    `gorm:"size:64;not null" json:"sha256"`
	FolderID    *int64    `gorm:"index" json:"folder_id,omitempty"`
	Status      string    `gorm:"size:20;not null;default:pending" json:"status"`
	MinioPrefix string    `gorm:"size:255;not null" json:"minio_prefix"`
	MimeType    string    `gorm:"size:255;default:'application/octet-stream'" json:"mime_type"`
	UserID      *int64    `gorm:"index" json:"user_id,omitempty"`
	ExpiresAt   time.Time `gorm:"not null" json:"expires_at"`
	CreatedAt   time.Time `json:"created_at"`
	UpdatedAt   time.Time `json:"updated_at"`
}

func (UploadSession) TableName() string {
	return "hpc_upload_sessions"
}

// UploadChunk represents a single chunk of an upload session.
type UploadChunk struct {
	ID         int64     `gorm:"primaryKey;autoIncrement" json:"id"`
	SessionID  int64     `gorm:"not null;uniqueIndex:idx_session_chunk" json:"session_id"`
	ChunkIndex int       `gorm:"not null;uniqueIndex:idx_session_chunk" json:"chunk_index"`
	MinioKey   string    `gorm:"size:255;not null" json:"minio_key"`
	SHA256     string    `gorm:"size:64" json:"sha256,omitempty"`
	Size       int64     `gorm:"not null" json:"size"`
	Status     string    `gorm:"size:20;not null;default:pending" json:"status"`
	CreatedAt  time.Time `json:"created_at"`
	UpdatedAt  time.Time `json:"updated_at"`
}

func (UploadChunk) TableName() string {
	return "hpc_upload_chunks"
}

// InitUploadRequest is the DTO for initiating a chunked upload.
type InitUploadRequest struct {
	FileName  string `json:"file_name" binding:"required"`
	FileSize  int64  `json:"file_size" binding:"required"`
	SHA256    string `json:"sha256" binding:"required"`
	FolderID  *int64 `json:"folder_id,omitempty"`
	ChunkSize *int64 `json:"chunk_size,omitempty"`
	MimeType  string `json:"mime_type,omitempty"`
}

// CreateFolderRequest is the DTO for creating a new folder.
type CreateFolderRequest struct {
	Name     string `json:"name" binding:"required"`
	ParentID *int64 `json:"parent_id,omitempty"`
}

// UploadSessionResponse is the DTO returned when creating/querying an upload session.
type UploadSessionResponse struct {
	ID             int64     `json:"id"`
	FileName       string    `json:"file_name"`
	FileSize       int64     `json:"file_size"`
	ChunkSize      int64     `json:"chunk_size"`
	TotalChunks    int       `json:"total_chunks"`
	SHA256         string    `json:"sha256"`
	Status         string    `json:"status"`
	UploadedChunks []int     `json:"uploaded_chunks"`
	ExpiresAt      time.Time `json:"expires_at"`
	CreatedAt      time.Time `json:"created_at"`
}

// FileResponse is the DTO for a file in API responses.
type FileResponse struct {
	ID        int64     `json:"id"`
	Name      string    `json:"name"`
	FolderID  *int64    `json:"folder_id,omitempty"`
	Size      int64     `json:"size"`
	MimeType  string    `json:"mime_type"`
	SHA256    string    `json:"sha256"`
	CreatedAt time.Time `json:"created_at"`
	UpdatedAt time.Time `json:"updated_at"`
}

// FolderResponse is the DTO for a folder in API responses.
type FolderResponse struct {
	ID             int64     `json:"id"`
	Name           string    `json:"name"`
	ParentID       *int64    `json:"parent_id,omitempty"`
	Path           string    `json:"path"`
	FileCount      int64     `json:"file_count"`
	SubFolderCount int64     `json:"subfolder_count"`
	CreatedAt      time.Time `json:"created_at"`
}

// ListFilesResponse is the paginated response for listing files.
type ListFilesResponse struct {
	Files    []FileResponse `json:"files"`
	Total    int64          `json:"total"`
	Page     int            `json:"page"`
	PageSize int            `json:"page_size"`
}

// ValidateFileName rejects empty, "..", "/", "\", null bytes, control chars, leading/trailing spaces.
func ValidateFileName(name string) error {
	if name == "" {
		return fmt.Errorf("file name cannot be empty")
	}
	if strings.TrimSpace(name) != name {
		return fmt.Errorf("file name cannot have leading or trailing spaces")
	}
	if name == ".." {
		return fmt.Errorf("file name cannot be '..'")
	}
	if strings.Contains(name, "/") || strings.Contains(name, "\\") {
		return fmt.Errorf("file name cannot contain '/' or '\\'")
	}
	for _, r := range name {
		if r == 0 {
			return fmt.Errorf("file name cannot contain null bytes")
		}
		if unicode.IsControl(r) {
			return fmt.Errorf("file name cannot contain control characters")
		}
	}
	return nil
}

// ValidateFolderName rejects same as ValidateFileName plus ".".
func ValidateFolderName(name string) error {
	if name == "." {
		return fmt.Errorf("folder name cannot be '.'")
	}
	return ValidateFileName(name)
}