// Copyright (C) 2021 Storj Labs, Inc.
// See LICENSE for copying information.

package ulfs

import (
	"context"
	"io"
	"os"
	"time"

	"github.com/zeebo/clingy"
	"github.com/zeebo/errs"

	"storj.io/storj/cmd/uplinkng/ulloc"
	"storj.io/uplink"
)

// ListOptions describes options to the List command.
type ListOptions struct {
	Recursive bool
	Pending   bool
	Expanded  bool
}

func (lo *ListOptions) isRecursive() bool { return lo != nil && lo.Recursive }
func (lo *ListOptions) isPending() bool   { return lo != nil && lo.Pending }

// RemoveOptions describes options to the Remove command.
type RemoveOptions struct {
	Pending bool
}

func (ro *RemoveOptions) isPending() bool { return ro != nil && ro.Pending }

// Filesystem represents either the local Filesystem or the data backed by a project.
type Filesystem interface {
	Close() error
	Open(ctx clingy.Context, loc ulloc.Location) (MultiReadHandle, error)
	Create(ctx clingy.Context, loc ulloc.Location) (WriteHandle, error)
	Move(ctx clingy.Context, source, dest ulloc.Location) error
	Remove(ctx context.Context, loc ulloc.Location, opts *RemoveOptions) error
	List(ctx context.Context, prefix ulloc.Location, opts *ListOptions) (ObjectIterator, error)
	IsLocalDir(ctx context.Context, loc ulloc.Location) bool
	Stat(ctx context.Context, loc ulloc.Location) (*ObjectInfo, error)
}

//
// object info
//

// ObjectInfo is a simpler *uplink.Object that contains the minimal information the
// uplink command needs that multiple types can be converted to.
type ObjectInfo struct {
	Loc           ulloc.Location
	IsPrefix      bool
	Created       time.Time
	ContentLength int64
	Expires       time.Time
	Metadata      uplink.CustomMetadata
}

// uplinkObjectToObjectInfo returns an objectInfo converted from an *uplink.Object.
func uplinkObjectToObjectInfo(bucket string, obj *uplink.Object) ObjectInfo {
	return ObjectInfo{
		Loc:           ulloc.NewRemote(bucket, obj.Key),
		IsPrefix:      obj.IsPrefix,
		Created:       obj.System.Created,
		ContentLength: obj.System.ContentLength,
		Expires:       obj.System.Expires,
		Metadata:      obj.Custom,
	}
}

// uplinkUploadInfoToObjectInfo returns an objectInfo converted from an *uplink.Object.
func uplinkUploadInfoToObjectInfo(bucket string, upl *uplink.UploadInfo) ObjectInfo {
	return ObjectInfo{
		Loc:           ulloc.NewRemote(bucket, upl.Key),
		IsPrefix:      upl.IsPrefix,
		Created:       upl.System.Created,
		ContentLength: upl.System.ContentLength,
		Expires:       upl.System.Expires,
		Metadata:      upl.Custom,
	}
}

//
// read handles
//

// MultiReadHandle allows one to read different sections of something.
// The offset parameter can be negative to signal that the offset should
// start that many bytes back from the end. Any negative value for length
// indicates to read up to the end.
//
// TODO: A negative offset requires a negative length, but there is no
// reason why that must be so.
type MultiReadHandle interface {
	io.Closer
	SetOffset(offset int64) error
	NextPart(ctx context.Context, length int64) (ReadHandle, error)
	Info(ctx context.Context) (*ObjectInfo, error)
}

// ReadHandle is something that can be read from distinct parts possibly
// in parallel.
type ReadHandle interface {
	io.Closer
	io.Reader
	Info() ObjectInfo
}

//
// write handles
//

// WriteHandle is anything that can be written to with commit/abort semantics.
type WriteHandle interface {
	io.Writer
	Commit() error
	Abort() error
}

// uplinkWriteHandle implements writeHandle for *uplink.Uploads.
type uplinkWriteHandle uplink.Upload

// newUplinkWriteHandle constructs an *uplinkWriteHandle from an *uplink.Upload.
func newUplinkWriteHandle(dl *uplink.Upload) *uplinkWriteHandle {
	return (*uplinkWriteHandle)(dl)
}

func (u *uplinkWriteHandle) raw() *uplink.Upload {
	return (*uplink.Upload)(u)
}

func (u *uplinkWriteHandle) Write(p []byte) (int, error) { return u.raw().Write(p) }
func (u *uplinkWriteHandle) Commit() error               { return u.raw().Commit() }
func (u *uplinkWriteHandle) Abort() error                { return u.raw().Abort() }

// osWriteHandle implements writeHandle for *os.Files.
type osWriteHandle struct {
	fh   *os.File
	done bool
}

// newOSWriteHandle constructs an *osWriteHandle from an *os.File.
func newOSWriteHandle(fh *os.File) *osWriteHandle {
	return &osWriteHandle{fh: fh}
}

func (o *osWriteHandle) Write(p []byte) (int, error) { return o.fh.Write(p) }

func (o *osWriteHandle) Commit() error {
	if o.done {
		return nil
	}
	o.done = true

	return o.fh.Close()
}

func (o *osWriteHandle) Abort() error {
	if o.done {
		return nil
	}
	o.done = true

	return errs.Combine(
		o.fh.Close(),
		os.Remove(o.fh.Name()),
	)
}

// genericWriteHandle implements writeHandle for an io.Writer.
type genericWriteHandle struct{ w io.Writer }

// newGenericWriteHandle constructs a *genericWriteHandle from an io.Writer.
func newGenericWriteHandle(w io.Writer) *genericWriteHandle {
	return &genericWriteHandle{w: w}
}

func (g *genericWriteHandle) Write(p []byte) (int, error) { return g.w.Write(p) }
func (g *genericWriteHandle) Commit() error               { return nil }
func (g *genericWriteHandle) Abort() error                { return nil }

//
// object iteration
//

// ObjectIterator is an interface type for iterating over objectInfo values.
type ObjectIterator interface {
	Next() bool
	Err() error
	Item() ObjectInfo
}

// filteredObjectIterator removes any iteration entries that do not begin with the filter.
// all entries must begin with the trim string which is removed before checking for the
// filter.
type filteredObjectIterator struct {
	trim   ulloc.Location
	filter ulloc.Location
	iter   ObjectIterator
}

func (f *filteredObjectIterator) Next() bool {
	for {
		if !f.iter.Next() {
			return false
		}
		loc := f.iter.Item().Loc
		if !loc.HasPrefix(f.trim) {
			return false
		}
		if loc.HasPrefix(f.filter.AsDirectoryish()) || loc == f.filter {
			return true
		}
	}
}

func (f *filteredObjectIterator) Err() error { return f.iter.Err() }

func (f *filteredObjectIterator) Item() ObjectInfo {
	item := f.iter.Item()
	item.Loc = item.Loc.RemovePrefix(f.trim)
	return item
}

// emptyObjectIterator is an objectIterator that has no objects.
type emptyObjectIterator struct{}

func (emptyObjectIterator) Next() bool       { return false }
func (emptyObjectIterator) Err() error       { return nil }
func (emptyObjectIterator) Item() ObjectInfo { return ObjectInfo{} }