// Copyright (c) 2021, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE file distributed with the sources of this project regarding your
// rights to use or distribute this software.

package sif

import (
	"crypto"
	"errors"
	"fmt"
	"io"
	"os"
	"time"
)

// descriptorOpts accumulates data object options.
type descriptorOpts struct {
	groupID   uint32
	linkID    uint32
	alignment int
	name      string
	extra     interface{}
	t         time.Time
}

// DescriptorInputOpt are used to specify data object options.
type DescriptorInputOpt func(DataType, *descriptorOpts) error

// OptNoGroup specifies the data object is not contained within a data object group.
func OptNoGroup() DescriptorInputOpt {
	return func(_ DataType, opts *descriptorOpts) error {
		opts.groupID = 0
		return nil
	}
}

// OptGroupID specifies groupID as data object group ID.
func OptGroupID(groupID uint32) DescriptorInputOpt {
	return func(_ DataType, opts *descriptorOpts) error {
		if groupID == 0 {
			return ErrInvalidGroupID
		}
		opts.groupID = groupID
		return nil
	}
}

// OptLinkedID specifies that the data object is linked to the data object with the specified ID.
func OptLinkedID(id uint32) DescriptorInputOpt {
	return func(_ DataType, opts *descriptorOpts) error {
		if id == 0 {
			return ErrInvalidObjectID
		}
		opts.linkID = id
		return nil
	}
}

// OptLinkedGroupID specifies that the data object is linked to the data object group with the
// specified groupID.
func OptLinkedGroupID(groupID uint32) DescriptorInputOpt {
	return func(_ DataType, opts *descriptorOpts) error {
		if groupID == 0 {
			return ErrInvalidGroupID
		}
		opts.linkID = groupID | descrGroupMask
		return nil
	}
}

// OptObjectAlignment specifies n as the data alignment requirement.
func OptObjectAlignment(n int) DescriptorInputOpt {
	return func(_ DataType, opts *descriptorOpts) error {
		opts.alignment = n
		return nil
	}
}

// OptObjectName specifies name as the data object name.
func OptObjectName(name string) DescriptorInputOpt {
	return func(_ DataType, opts *descriptorOpts) error {
		opts.name = name
		return nil
	}
}

// OptObjectTime specifies t as the data object creation time.
func OptObjectTime(t time.Time) DescriptorInputOpt {
	return func(_ DataType, opts *descriptorOpts) error {
		opts.t = t
		return nil
	}
}

type unexpectedDataTypeError struct {
	got  DataType
	want []DataType
}

func (e *unexpectedDataTypeError) Error() string {
	return fmt.Sprintf("unexpected data type %v, expected one of: %v", e.got, e.want)
}

func (e *unexpectedDataTypeError) Is(target error) bool {
	//nolint:errorlint // don't compare wrapped errors in Is()
	t, ok := target.(*unexpectedDataTypeError)
	if !ok {
		return false
	}

	if len(t.want) > 0 {
		// Use a map to check that the "want" errors in e and t contain the same values, ignoring
		// any ordering differences.
		acc := make(map[DataType]int, len(t.want))

		// Increment counter for each data type in e.
		for _, dt := range e.want {
			if _, ok := acc[dt]; !ok {
				acc[dt] = 0
			}
			acc[dt]++
		}

		// Decrement counter for each data type in e.
		for _, dt := range t.want {
			if _, ok := acc[dt]; !ok {
				return false
			}
			acc[dt]--
		}

		// If the "want" errors in e and t are equivalent, all counters should be zero.
		for _, n := range acc {
			if n != 0 {
				return false
			}
		}
	}

	return (e.got == t.got || t.got == 0)
}

// OptCryptoMessageMetadata sets metadata for a crypto message data object. The format type is set
// to ft, and the message type is set to mt.
//
// If this option is applied to a data object with an incompatible type, an error is returned.
func OptCryptoMessageMetadata(ft FormatType, mt MessageType) DescriptorInputOpt {
	return func(t DataType, opts *descriptorOpts) error {
		if got, want := t, DataCryptoMessage; got != want {
			return &unexpectedDataTypeError{got, []DataType{want}}
		}

		m := cryptoMessage{
			Formattype:  ft,
			Messagetype: mt,
		}

		opts.extra = m
		return nil
	}
}

var errUnknownArchitcture = errors.New("unknown architecture")

// OptPartitionMetadata sets metadata for a partition data object. The filesystem type is set to
// fs, the partition type is set to pt, and the CPU architecture is set to arch. The value of arch
// should be the architecture as represented by the Go runtime.
//
// If this option is applied to a data object with an incompatible type, an error is returned.
func OptPartitionMetadata(fs FSType, pt PartType, arch string) DescriptorInputOpt {
	return func(t DataType, opts *descriptorOpts) error {
		if got, want := t, DataPartition; got != want {
			return &unexpectedDataTypeError{got, []DataType{want}}
		}

		sifarch := getSIFArch(arch)
		if sifarch == hdrArchUnknown {
			return fmt.Errorf("%w: %v", errUnknownArchitcture, arch)
		}

		p := partition{
			Fstype:   fs,
			Parttype: pt,
			Arch:     sifarch,
		}

		opts.extra = p
		return nil
	}
}

// sifHashType converts h into a HashType.
func sifHashType(h crypto.Hash) hashType {
	switch h {
	case crypto.SHA256:
		return hashSHA256
	case crypto.SHA384:
		return hashSHA384
	case crypto.SHA512:
		return hashSHA512
	case crypto.BLAKE2s_256:
		return hashBLAKE2S
	case crypto.BLAKE2b_256:
		return hashBLAKE2B
	}
	return 0
}

// OptSignatureMetadata sets metadata for a signature data object. The hash type is set to ht, and
// the signing entity fingerprint is set to fp.
//
// If this option is applied to a data object with an incompatible type, an error is returned.
func OptSignatureMetadata(ht crypto.Hash, fp []byte) DescriptorInputOpt {
	return func(t DataType, opts *descriptorOpts) error {
		if got, want := t, DataSignature; got != want {
			return &unexpectedDataTypeError{got, []DataType{want}}
		}

		s := signature{
			Hashtype: sifHashType(ht),
		}
		copy(s.Entity[:], fp)

		opts.extra = s
		return nil
	}
}

// DescriptorInput describes a new data object.
type DescriptorInput struct {
	dt   DataType
	r    io.Reader
	opts descriptorOpts
}

// DefaultObjectGroup is the default group that data objects are placed in.
const DefaultObjectGroup = 1

// NewDescriptorInput returns a DescriptorInput representing a data object of type t, with contents
// read from r, configured according to opts.
//
// It is possible (and often necessary) to store additional metadata related to certain types of
// data objects. Consider supplying options such as OptCryptoMessageMetadata, OptPartitionMetadata,
// and OptSignatureMetadata for this purpose.
//
// By default, the data object will be placed in the default data object group (1). To override
// this behavior, use OptNoGroup or OptGroupID. To link this data object, use OptLinkedID or
// OptLinkedGroupID.
//
// By default, the data object will be aligned according to the system's memory page size. To
// override this behavior, consider using OptObjectAlignment.
//
// By default, no name is set for data object. To set a name, use OptObjectName.
//
// When creating a new image, data object creation/modification times are set to the image creation
// time. When modifying an existing image, the data object creation/modification time is set to the
// image modification time. To override this behavior, consider using OptObjectTime.
func NewDescriptorInput(t DataType, r io.Reader, opts ...DescriptorInputOpt) (DescriptorInput, error) {
	dopts := descriptorOpts{
		groupID:   DefaultObjectGroup,
		alignment: os.Getpagesize(),
	}

	for _, opt := range opts {
		if err := opt(t, &dopts); err != nil {
			return DescriptorInput{}, fmt.Errorf("%w", err)
		}
	}

	di := DescriptorInput{
		dt:   t,
		r:    r,
		opts: dopts,
	}

	return di, nil
}

// fillDescriptor fills d according to di. If di does not explicitly specify a time value, use t.
func (di DescriptorInput) fillDescriptor(t time.Time, d *rawDescriptor) error {
	d.DataType = di.dt
	d.GroupID = di.opts.groupID | descrGroupMask
	d.LinkedID = di.opts.linkID

	if !di.opts.t.IsZero() {
		t = di.opts.t
	}
	d.CreatedAt = t.Unix()
	d.ModifiedAt = t.Unix()

	d.UID = 0
	d.GID = 0

	if err := d.setName(di.opts.name); err != nil {
		return err
	}

	return d.setExtra(di.opts.extra)
}
