package llb

import (
	"context"
	_ "crypto/sha256"
	"encoding/json"
	"os"
	"strconv"
	"strings"

	"github.com/docker/distribution/reference"
	"github.com/moby/buildkit/solver/pb"
	digest "github.com/opencontainers/go-digest"
	"github.com/pkg/errors"
)

type SourceOp struct {
	id               string
	attrs            map[string]string
	output           Output
	cachedPB         []byte
	cachedOpMetadata *pb.OpMetadata
	err              error
}

func NewSource(id string, attrs map[string]string) *SourceOp {
	s := &SourceOp{
		id:    id,
		attrs: attrs,
	}
	s.output = &output{vertex: s}
	return s
}

func (s *SourceOp) Validate() error {
	if s.err != nil {
		return s.err
	}
	if s.id == "" {
		return errors.Errorf("source identifier can't be empty")
	}
	return nil
}

func (s *SourceOp) Marshal() ([]byte, *pb.OpMetadata, error) {
	if s.cachedPB != nil {
		return s.cachedPB, s.cachedOpMetadata, nil
	}
	if err := s.Validate(); err != nil {
		return nil, nil, err
	}

	proto := &pb.Op{
		Op: &pb.Op_Source{
			Source: &pb.SourceOp{Identifier: s.id, Attrs: s.attrs},
		},
	}
	dt, err := proto.Marshal()
	if err != nil {
		return nil, nil, err
	}
	s.cachedPB = dt
	s.cachedOpMetadata = &pb.OpMetadata{}
	return dt, s.cachedOpMetadata, nil
}

func (s *SourceOp) Output() Output {
	return s.output
}

func (s *SourceOp) Inputs() []Output {
	return nil
}

func Source(id string) State {
	return NewState(NewSource(id, nil).Output())
}

func Image(ref string, opts ...ImageOption) State {
	r, err := reference.ParseNormalizedNamed(ref)
	if err == nil {
		ref = reference.TagNameOnly(r).String()
	}
	src := NewSource("docker-image://"+ref, nil) // controversial
	if err != nil {
		src.err = err
	}
	var info ImageInfo
	for _, opt := range opts {
		opt(&info)
	}
	if info.metaResolver != nil {
		_, dt, err := info.metaResolver.ResolveImageConfig(context.TODO(), ref)
		if err != nil {
			src.err = err
		} else {
			var img struct {
				Config struct {
					Env        []string `json:"Env,omitempty"`
					WorkingDir string   `json:"WorkingDir,omitempty"`
					User       string   `json:"User,omitempty"`
				} `json:"config,omitempty"`
			}
			if err := json.Unmarshal(dt, &img); err != nil {
				src.err = err
			} else {
				st := NewState(src.Output())
				for _, env := range img.Config.Env {
					parts := strings.SplitN(env, "=", 2)
					if len(parts[0]) > 0 {
						var v string
						if len(parts) > 1 {
							v = parts[1]
						}
						st = st.AddEnv(parts[0], v)
					}
				}
				st = st.Dir(img.Config.WorkingDir)
				return st
			}
		}
	}
	return NewState(src.Output())
}

type ImageOption func(*ImageInfo)

type ImageInfo struct {
	metaResolver ImageMetaResolver
}

func Git(remote, ref string, opts ...GitOption) State {
	id := remote
	if ref != "" {
		id += "#" + ref
	}

	gi := &GitInfo{}
	for _, o := range opts {
		o(gi)
	}
	attrs := map[string]string{}
	if gi.KeepGitDir {
		attrs[pb.AttrKeepGitDir] = "true"
	}

	source := NewSource("git://"+id, attrs)
	return NewState(source.Output())
}

type GitOption func(*GitInfo)

type GitInfo struct {
	KeepGitDir bool
}

func KeepGitDir() GitOption {
	return func(gi *GitInfo) {
		gi.KeepGitDir = true
	}
}

func Scratch() State {
	return NewState(nil)
}

func Local(name string, opts ...LocalOption) State {
	gi := &LocalInfo{}

	for _, o := range opts {
		o(gi)
	}
	attrs := map[string]string{}
	if gi.SessionID != "" {
		attrs[pb.AttrLocalSessionID] = gi.SessionID
	}
	if gi.IncludePatterns != "" {
		attrs[pb.AttrIncludePatterns] = gi.IncludePatterns
	}

	source := NewSource("local://"+name, attrs)
	return NewState(source.Output())
}

type LocalOption func(*LocalInfo)

func SessionID(id string) LocalOption {
	return func(li *LocalInfo) {
		li.SessionID = id
	}
}

func IncludePatterns(p []string) LocalOption {
	return func(li *LocalInfo) {
		dt, _ := json.Marshal(p) // empty on error
		li.IncludePatterns = string(dt)
	}
}

type LocalInfo struct {
	SessionID       string
	IncludePatterns string
}

func HTTP(url string, opts ...HTTPOption) State {
	hi := &HTTPInfo{}
	for _, o := range opts {
		o(hi)
	}
	attrs := map[string]string{}
	if hi.Checksum != "" {
		attrs[pb.AttrHTTPChecksum] = hi.Checksum.String()
	}
	if hi.Filename != "" {
		attrs[pb.AttrHTTPFilename] = hi.Filename
	}
	if hi.Perm != 0 {
		attrs[pb.AttrHTTPPerm] = "0" + strconv.FormatInt(int64(hi.Perm), 8)
	}
	if hi.UID != 0 {
		attrs[pb.AttrHTTPUID] = strconv.Itoa(hi.UID)
	}
	if hi.UID != 0 {
		attrs[pb.AttrHTTPGID] = strconv.Itoa(hi.GID)
	}

	source := NewSource(url, attrs)
	return NewState(source.Output())
}

type HTTPInfo struct {
	Checksum digest.Digest
	Filename string
	Perm     int
	UID      int
	GID      int
}

type HTTPOption func(*HTTPInfo)

func Checksum(dgst digest.Digest) HTTPOption {
	return func(hi *HTTPInfo) {
		hi.Checksum = dgst
	}
}

func Chmod(perm os.FileMode) HTTPOption {
	return func(hi *HTTPInfo) {
		hi.Perm = int(perm) & 0777
	}
}

func Filename(name string) HTTPOption {
	return func(hi *HTTPInfo) {
		hi.Filename = name
	}
}

func Chown(uid, gid int) HTTPOption {
	return func(hi *HTTPInfo) {
		hi.UID = uid
		hi.GID = gid
	}
}