gitech

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// Copyright 2023 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package git
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import (
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	"crypto/sha1"
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	"crypto/sha256"
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	"regexp"
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	"strconv"
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)
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// sha1Pattern can be used to determine if a string is an valid sha
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var sha1Pattern = regexp.MustCompile(`^[0-9a-f]{4,40}$`)
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// sha256Pattern can be used to determine if a string is an valid sha
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var sha256Pattern = regexp.MustCompile(`^[0-9a-f]{4,64}$`)
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type ObjectFormat interface {
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	// Name returns the name of the object format
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	Name() string
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	// EmptyObjectID creates a new empty ObjectID from an object format hash name
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	EmptyObjectID() ObjectID
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	// EmptyTree is the hash of an empty tree
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	EmptyTree() ObjectID
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	// FullLength is the length of the hash's hex string
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	FullLength() int
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	// IsValid returns true if the input is a valid hash
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	IsValid(input string) bool
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	// MustID creates a new ObjectID from a byte slice
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	MustID(b []byte) ObjectID
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	// ComputeHash compute the hash for a given ObjectType and content
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	ComputeHash(t ObjectType, content []byte) ObjectID
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}
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/* SHA1 Type */
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type Sha1ObjectFormatImpl struct{}
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var (
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	emptySha1ObjectID = &Sha1Hash{}
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	emptySha1Tree     = &Sha1Hash{
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		0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
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		0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04,
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	}
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)
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func (Sha1ObjectFormatImpl) Name() string { return "sha1" }
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func (Sha1ObjectFormatImpl) EmptyObjectID() ObjectID {
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	return emptySha1ObjectID
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}
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func (Sha1ObjectFormatImpl) EmptyTree() ObjectID {
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	return emptySha1Tree
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}
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func (Sha1ObjectFormatImpl) FullLength() int { return 40 }
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func (Sha1ObjectFormatImpl) IsValid(input string) bool {
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	return sha1Pattern.MatchString(input)
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}
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func (Sha1ObjectFormatImpl) MustID(b []byte) ObjectID {
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	var id Sha1Hash
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	copy(id[0:20], b)
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	return &id
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}
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// ComputeHash compute the hash for a given ObjectType and content
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func (h Sha1ObjectFormatImpl) ComputeHash(t ObjectType, content []byte) ObjectID {
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	hasher := sha1.New()
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	_, _ = hasher.Write(t.Bytes())
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	_, _ = hasher.Write([]byte(" "))
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	_, _ = hasher.Write([]byte(strconv.FormatInt(int64(len(content)), 10)))
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	_, _ = hasher.Write([]byte{0})
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	// HashSum generates a SHA1 for the provided hash
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	var sha1 Sha1Hash
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	copy(sha1[:], hasher.Sum(nil))
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	return &sha1
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}
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/* SHA256 Type */
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type Sha256ObjectFormatImpl struct{}
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var (
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	emptySha256ObjectID = &Sha256Hash{}
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	emptySha256Tree     = &Sha256Hash{
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		0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1,
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		0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5,
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		0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc,
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		0x53, 0x21,
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	}
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)
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func (Sha256ObjectFormatImpl) Name() string { return "sha256" }
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func (Sha256ObjectFormatImpl) EmptyObjectID() ObjectID {
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	return emptySha256ObjectID
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}
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func (Sha256ObjectFormatImpl) EmptyTree() ObjectID {
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	return emptySha256Tree
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}
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func (Sha256ObjectFormatImpl) FullLength() int { return 64 }
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func (Sha256ObjectFormatImpl) IsValid(input string) bool {
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	return sha256Pattern.MatchString(input)
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}
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func (Sha256ObjectFormatImpl) MustID(b []byte) ObjectID {
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	var id Sha256Hash
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	copy(id[0:32], b)
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	return &id
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}
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// ComputeHash compute the hash for a given ObjectType and content
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func (h Sha256ObjectFormatImpl) ComputeHash(t ObjectType, content []byte) ObjectID {
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	hasher := sha256.New()
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	_, _ = hasher.Write(t.Bytes())
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	_, _ = hasher.Write([]byte(" "))
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	_, _ = hasher.Write([]byte(strconv.FormatInt(int64(len(content)), 10)))
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	_, _ = hasher.Write([]byte{0})
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	// HashSum generates a SHA256 for the provided hash
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	var sha256 Sha1Hash
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	copy(sha256[:], hasher.Sum(nil))
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	return &sha256
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}
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var (
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	Sha1ObjectFormat   ObjectFormat = Sha1ObjectFormatImpl{}
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	Sha256ObjectFormat ObjectFormat = Sha256ObjectFormatImpl{}
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)
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var SupportedObjectFormats = []ObjectFormat{
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	Sha1ObjectFormat,
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}
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func ObjectFormatFromName(name string) ObjectFormat {
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	for _, objectFormat := range SupportedObjectFormats {
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		if name == objectFormat.Name() {
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			return objectFormat
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		}
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	}
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	return nil
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}
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func IsValidObjectFormat(name string) bool {
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	return ObjectFormatFromName(name) != nil
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}
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