/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package docker

import (
	"errors"
	"fmt"
	"strings"

	"github.com/opencontainers/go-digest"
)

var (
	legacyDefaultDomain = "index.docker.io"
	defaultDomain       = "docker.io"
	officialRepoName    = "library"
	defaultTag          = "latest"
)

// normalizedNamed represents a name which has been
// normalized and has a familiar form. A familiar name
// is what is used in Docker UI. An example normalized
// name is "docker.io/library/ubuntu" and corresponding
// familiar name of "ubuntu".
type normalizedNamed interface {
	Named
	Familiar() Named
}

// ParseNormalizedNamed parses a string into a named reference
// transforming a familiar name from Docker UI to a fully
// qualified reference. If the value may be an identifier
// use ParseAnyReference.
func ParseNormalizedNamed(s string) (Named, error) {
	if ok := anchoredIdentifierRegexp.MatchString(s); ok {
		return nil, fmt.Errorf("invalid repository name (%s), cannot specify 64-byte hexadecimal strings", s)
	}
	domain, remainder := splitDockerDomain(s)
	var remoteName string
	if tagSep := strings.IndexRune(remainder, ':'); tagSep > -1 {
		remoteName = remainder[:tagSep]
	} else {
		remoteName = remainder
	}
	if strings.ToLower(remoteName) != remoteName {
		return nil, errors.New("invalid reference format: repository name must be lowercase")
	}

	ref, err := Parse(domain + "/" + remainder)
	if err != nil {
		return nil, err
	}
	named, isNamed := ref.(Named)
	if !isNamed {
		return nil, fmt.Errorf("reference %s has no name", ref.String())
	}
	return named, nil
}

// ParseDockerRef normalizes the image reference following the docker convention. This is added
// mainly for backward compatibility.
// The reference returned can only be either tagged or digested. For reference contains both tag
// and digest, the function returns digested reference, e.g. docker.io/library/busybox:latest@
// sha256:7cc4b5aefd1d0cadf8d97d4350462ba51c694ebca145b08d7d41b41acc8db5aa will be returned as
// docker.io/library/busybox@sha256:7cc4b5aefd1d0cadf8d97d4350462ba51c694ebca145b08d7d41b41acc8db5aa.
func ParseDockerRef(ref string) (Named, error) {
	named, err := ParseNormalizedNamed(ref)
	if err != nil {
		return nil, err
	}
	if _, ok := named.(NamedTagged); ok {
		if canonical, ok := named.(Canonical); ok {
			// The reference is both tagged and digested, only
			// return digested.
			newNamed, err := WithName(canonical.Name())
			if err != nil {
				return nil, err
			}
			newCanonical, err := WithDigest(newNamed, canonical.Digest())
			if err != nil {
				return nil, err
			}
			return newCanonical, nil
		}
	}
	return TagNameOnly(named), nil
}

// splitDockerDomain splits a repository name to domain and remotename string.
// If no valid domain is found, the default domain is used. Repository name
// needs to be already validated before.
func splitDockerDomain(name string) (domain, remainder string) {
	i := strings.IndexRune(name, '/')
	if i == -1 || (!strings.ContainsAny(name[:i], ".:") && name[:i] != "localhost") {
		domain, remainder = defaultDomain, name
	} else {
		domain, remainder = name[:i], name[i+1:]
	}
	if domain == legacyDefaultDomain {
		domain = defaultDomain
	}
	if domain == defaultDomain && !strings.ContainsRune(remainder, '/') {
		remainder = officialRepoName + "/" + remainder
	}
	return
}

// familiarizeName returns a shortened version of the name familiar
// to to the Docker UI. Familiar names have the default domain
// "docker.io" and "library/" repository prefix removed.
// For example, "docker.io/library/redis" will have the familiar
// name "redis" and "docker.io/dmcgowan/myapp" will be "dmcgowan/myapp".
// Returns a familiarized named only reference.
func familiarizeName(named namedRepository) repository {
	repo := repository{
		domain: named.Domain(),
		path:   named.Path(),
	}

	if repo.domain == defaultDomain {
		repo.domain = ""
		// Handle official repositories which have the pattern "library/<official repo name>"
		if split := strings.Split(repo.path, "/"); len(split) == 2 && split[0] == officialRepoName {
			repo.path = split[1]
		}
	}
	return repo
}

func (r reference) Familiar() Named {
	return reference{
		namedRepository: familiarizeName(r.namedRepository),
		tag:             r.tag,
		digest:          r.digest,
	}
}

func (r repository) Familiar() Named {
	return familiarizeName(r)
}

func (t taggedReference) Familiar() Named {
	return taggedReference{
		namedRepository: familiarizeName(t.namedRepository),
		tag:             t.tag,
	}
}

func (c canonicalReference) Familiar() Named {
	return canonicalReference{
		namedRepository: familiarizeName(c.namedRepository),
		digest:          c.digest,
	}
}

// TagNameOnly adds the default tag "latest" to a reference if it only has
// a repo name.
func TagNameOnly(ref Named) Named {
	if IsNameOnly(ref) {
		namedTagged, err := WithTag(ref, defaultTag)
		if err != nil {
			// Default tag must be valid, to create a NamedTagged
			// type with non-validated input the WithTag function
			// should be used instead
			panic(err)
		}
		return namedTagged
	}
	return ref
}

// ParseAnyReference parses a reference string as a possible identifier,
// full digest, or familiar name.
func ParseAnyReference(ref string) (Reference, error) {
	if ok := anchoredIdentifierRegexp.MatchString(ref); ok {
		return digestReference("sha256:" + ref), nil
	}
	if dgst, err := digest.Parse(ref); err == nil {
		return digestReference(dgst), nil
	}

	return ParseNormalizedNamed(ref)
}