// Package object defines some useful Objects
package object

import (
	"bytes"
	"context"
	"errors"
	"io"
	"time"

	"github.com/rclone/rclone/fs"
	"github.com/rclone/rclone/fs/hash"
)

// StaticObjectInfo is an ObjectInfo which can be constructed from scratch
type StaticObjectInfo struct {
	remote   string
	modTime  time.Time
	size     int64
	storable bool
	hashes   map[hash.Type]string
	fs       fs.Info
	meta     fs.Metadata
	mimeType string
}

// NewStaticObjectInfo returns a static ObjectInfo
// If hashes is nil and fs is not nil, the hash map will be replaced with
// empty hashes of the types supported by the fs.
func NewStaticObjectInfo(remote string, modTime time.Time, size int64, storable bool, hashes map[hash.Type]string, f fs.Info) *StaticObjectInfo {
	info := &StaticObjectInfo{
		remote:   remote,
		modTime:  modTime,
		size:     size,
		storable: storable,
		hashes:   hashes,
		fs:       f,
	}
	if f != nil && hashes == nil {
		set := f.Hashes().Array()
		info.hashes = make(map[hash.Type]string)
		for _, ht := range set {
			info.hashes[ht] = ""
		}
	}
	if f == nil {
		info.fs = MemoryFs
	}
	return info
}

// WithMetadata adds meta to the ObjectInfo
func (i *StaticObjectInfo) WithMetadata(meta fs.Metadata) *StaticObjectInfo {
	i.meta = meta
	return i
}

// WithMimeType adds meta to the ObjectInfo
func (i *StaticObjectInfo) WithMimeType(mimeType string) *StaticObjectInfo {
	i.mimeType = mimeType
	return i
}

// Fs returns read only access to the Fs that this object is part of
func (i *StaticObjectInfo) Fs() fs.Info {
	return i.fs
}

// Remote returns the remote path
func (i *StaticObjectInfo) Remote() string {
	return i.remote
}

// String returns a description of the Object
func (i *StaticObjectInfo) String() string {
	return i.remote
}

// ModTime returns the modification date of the file
func (i *StaticObjectInfo) ModTime(ctx context.Context) time.Time {
	return i.modTime
}

// Size returns the size of the file
func (i *StaticObjectInfo) Size() int64 {
	return i.size
}

// Storable says whether this object can be stored
func (i *StaticObjectInfo) Storable() bool {
	return i.storable
}

// Hash returns the requested hash of the contents
func (i *StaticObjectInfo) Hash(ctx context.Context, h hash.Type) (string, error) {
	if len(i.hashes) == 0 {
		return "", hash.ErrUnsupported
	}
	if hash, ok := i.hashes[h]; ok {
		return hash, nil
	}
	return "", hash.ErrUnsupported
}

// Metadata on the object
func (i *StaticObjectInfo) Metadata(ctx context.Context) (fs.Metadata, error) {
	return i.meta, nil
}

// MimeType returns the content type of the Object if
// known, or "" if not
func (i *StaticObjectInfo) MimeType(ctx context.Context) string {
	return i.mimeType
}

// Check interfaces
var (
	_ fs.ObjectInfo = (*StaticObjectInfo)(nil)
	_ fs.Metadataer = (*StaticObjectInfo)(nil)
	_ fs.MimeTyper  = (*StaticObjectInfo)(nil)
)

// MemoryFs is an in memory Fs, it only supports FsInfo and Put
var MemoryFs memoryFs

// memoryFs is an in memory fs
type memoryFs struct{}

// Name of the remote (as passed into NewFs)
func (memoryFs) Name() string { return "memory" }

// Root of the remote (as passed into NewFs)
func (memoryFs) Root() string { return "" }

// String returns a description of the FS
func (memoryFs) String() string { return "memory" }

// Precision of the ModTimes in this Fs
func (memoryFs) Precision() time.Duration { return time.Nanosecond }

// Returns the supported hash types of the filesystem
func (memoryFs) Hashes() hash.Set { return hash.Supported() }

// Features returns the optional features of this Fs
func (memoryFs) Features() *fs.Features { return &fs.Features{} }

// List the objects and directories in dir into entries.  The
// entries can be returned in any order but should be for a
// complete directory.
//
// dir should be "" to list the root, and should not have
// trailing slashes.
//
// This should return ErrDirNotFound if the directory isn't
// found.
func (memoryFs) List(ctx context.Context, dir string) (entries fs.DirEntries, err error) {
	return nil, nil
}

// NewObject finds the Object at remote.  If it can't be found
// it returns the error ErrorObjectNotFound.
func (memoryFs) NewObject(ctx context.Context, remote string) (fs.Object, error) {
	return nil, fs.ErrorObjectNotFound
}

// Put in to the remote path with the modTime given of the given size
//
// May create the object even if it returns an error - if so
// will return the object and the error, otherwise will return
// nil and the error
func (memoryFs) Put(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
	o := NewMemoryObject(src.Remote(), src.ModTime(ctx), nil)
	return o, o.Update(ctx, in, src, options...)
}

// Mkdir makes the directory (container, bucket)
//
// Shouldn't return an error if it already exists
func (memoryFs) Mkdir(ctx context.Context, dir string) error {
	return errors.New("memoryFs: can't make directory")
}

// Rmdir removes the directory (container, bucket) if empty
//
// Return an error if it doesn't exist or isn't empty
func (memoryFs) Rmdir(ctx context.Context, dir string) error {
	return fs.ErrorDirNotFound
}

var _ fs.Fs = MemoryFs

// MemoryObject is an in memory object
type MemoryObject struct {
	remote   string
	modTime  time.Time
	content  []byte
	meta     fs.Metadata
	fs       fs.Fs
	mimeType string
}

// NewMemoryObject returns an in memory Object with the modTime and content passed in
func NewMemoryObject(remote string, modTime time.Time, content []byte) *MemoryObject {
	return &MemoryObject{
		remote:  remote,
		modTime: modTime,
		content: content,
		fs:      MemoryFs,
	}
}

// WithMetadata adds meta to the MemoryObject
func (o *MemoryObject) WithMetadata(meta fs.Metadata) *MemoryObject {
	o.meta = meta
	return o
}

// WithMimeType adds mimeType to the MemoryObject
func (o *MemoryObject) WithMimeType(mimeType string) *MemoryObject {
	o.mimeType = mimeType
	return o
}

// Content returns the underlying buffer
func (o *MemoryObject) Content() []byte {
	return o.content
}

// Fs returns read only access to the Fs that this object is part of
func (o *MemoryObject) Fs() fs.Info {
	return o.fs
}

// SetFs sets the Fs that this memory object thinks it is part of
// It will ignore nil f
func (o *MemoryObject) SetFs(f fs.Fs) *MemoryObject {
	if f != nil {
		o.fs = f
	}
	return o
}

// Remote returns the remote path
func (o *MemoryObject) Remote() string {
	return o.remote
}

// String returns a description of the Object
func (o *MemoryObject) String() string {
	return o.remote
}

// ModTime returns the modification date of the file
func (o *MemoryObject) ModTime(ctx context.Context) time.Time {
	return o.modTime
}

// Size returns the size of the file
func (o *MemoryObject) Size() int64 {
	return int64(len(o.content))
}

// Storable says whether this object can be stored
func (o *MemoryObject) Storable() bool {
	return true
}

// Hash returns the requested hash of the contents
func (o *MemoryObject) Hash(ctx context.Context, h hash.Type) (string, error) {
	hash, err := hash.NewMultiHasherTypes(hash.Set(h))
	if err != nil {
		return "", err
	}
	_, err = hash.Write(o.content)
	if err != nil {
		return "", err
	}
	return hash.Sums()[h], nil
}

// SetModTime sets the metadata on the object to set the modification date
func (o *MemoryObject) SetModTime(ctx context.Context, modTime time.Time) error {
	o.modTime = modTime
	return nil
}

// Open opens the file for read.  Call Close() on the returned io.ReadCloser
func (o *MemoryObject) Open(ctx context.Context, options ...fs.OpenOption) (io.ReadCloser, error) {
	var offset, limit int64 = 0, -1
	for _, option := range options {
		switch x := option.(type) {
		case *fs.RangeOption:
			offset, limit = x.Decode(o.Size())
		case *fs.SeekOption:
			offset = x.Offset
		default:
			if option.Mandatory() {
				fs.Logf(o, "Unsupported mandatory option: %v", option)
			}
		}
	}
	content := o.content
	offset = max(offset, 0)
	if limit < 0 {
		content = content[offset:]
	} else {
		content = content[offset:min(offset+limit, int64(len(content)))]
	}
	return io.NopCloser(bytes.NewBuffer(content)), nil
}

// Update in to the object with the modTime given of the given size
//
// This reuses the internal buffer if at all possible.
func (o *MemoryObject) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (err error) {
	size := src.Size()
	if size == 0 {
		o.content = nil
	} else if size < 0 || int64(cap(o.content)) < size {
		o.content, err = io.ReadAll(in)
	} else {
		o.content = o.content[:size]
		_, err = io.ReadFull(in, o.content)
	}
	o.modTime = src.ModTime(ctx)
	return err
}

// Remove this object
func (o *MemoryObject) Remove(ctx context.Context) error {
	return errors.New("memoryObject.Remove not supported")
}

// Metadata on the object
func (o *MemoryObject) Metadata(ctx context.Context) (fs.Metadata, error) {
	return o.meta, nil
}

// MimeType on the object
func (o *MemoryObject) MimeType(ctx context.Context) string {
	return o.mimeType
}

// Check interfaces
var (
	_ fs.Object     = (*MemoryObject)(nil)
	_ fs.MimeTyper  = (*MemoryObject)(nil)
	_ fs.Metadataer = (*MemoryObject)(nil)
)
