// Package dockerclient implements the Docker container/build defaults Target.
// It only edits the owning user's Docker client config.json and never contacts
// or changes a Docker daemon.
package dockerclient

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	"proxyctl/internal/profile"
	"proxyctl/internal/securefs"
	"proxyctl/internal/target"
)

var managedKeys = []string{"httpProxy", "httpsProxy", "allProxy", "noProxy"}

type Configuration struct {
	ConfigFile   string
	RecoveryFile string
	OwnFiles     bool
	UID          int
	GID          int
	TrustedRoots []string
}

// ResolveConfiguration keeps Docker client effects with the invoking user when
// proxyctl itself was explicitly started through sudo.
func ResolveConfiguration(environment profile.IdentityEnvironment) (Configuration, error) {
	profileConfiguration, err := profile.ResolveConfiguration(environment)
	if err != nil {
		return Configuration{}, err
	}
	owner := profileConfiguration.Owner
	current, err := environment.CurrentUser()
	if err != nil {
		return Configuration{}, fmt.Errorf("identify effective user: %w", err)
	}
	invokingUser := current.Username != owner.Username

	dockerDirectory := ""
	if value, ok := environment.LookupEnv("DOCKER_CONFIG"); ok && filepath.IsAbs(value) {
		if !invokingUser || pathWithin(value, owner.HomeDir) {
			dockerDirectory = value
		}
	}
	if dockerDirectory == "" {
		dockerDirectory = filepath.Join(owner.HomeDir, ".docker")
	}
	stateDirectory := ""
	if value, ok := environment.LookupEnv("XDG_STATE_HOME"); ok && filepath.IsAbs(value) {
		if !invokingUser || pathWithin(value, owner.HomeDir) {
			stateDirectory = value
		}
	}
	if stateDirectory == "" {
		stateDirectory = filepath.Join(owner.HomeDir, ".local", "state")
	}

	roots := []string{owner.HomeDir}
	if !pathWithin(dockerDirectory, owner.HomeDir) {
		roots = append(roots, filepath.Dir(dockerDirectory))
	}
	if !pathWithin(stateDirectory, owner.HomeDir) {
		roots = append(roots, filepath.Dir(stateDirectory))
	}
	return Configuration{
		ConfigFile:   filepath.Join(dockerDirectory, "config.json"),
		RecoveryFile: filepath.Join(stateDirectory, "proxyctl", "docker-containers.json"),
		OwnFiles:     true, UID: owner.UID, GID: owner.GID, TrustedRoots: roots,
	}, nil
}

func ResolveConfigurationForCurrentProcess() (Configuration, error) {
	return ResolveConfiguration(systemEnvironment{})
}

type systemEnvironment struct{}

func (systemEnvironment) CurrentUser() (profile.UserIdentity, error) {
	return profile.SystemCurrentUser()
}
func (systemEnvironment) LookupUser(name string) (profile.UserIdentity, error) {
	return profile.SystemLookupUser(name)
}
func (systemEnvironment) LookupEnv(name string) (string, bool) { return os.LookupEnv(name) }

func pathWithin(path, parent string) bool {
	relative, err := filepath.Rel(parent, path)
	return err == nil && relative != ".." && !strings.HasPrefix(relative, ".."+string(filepath.Separator))
}

type Ownership struct{ UID, GID int }

type FileSystem interface {
	ReadFile(string) ([]byte, error)
	AtomicWrite(string, []byte, os.FileMode, *Ownership) error
	Remove(string) error
	WithLock(string, *Ownership, func() error) error
}

type OSFileSystem struct{ TrustedRoots []string }

func NewOSFileSystem(configuration Configuration) OSFileSystem {
	return OSFileSystem{TrustedRoots: append([]string(nil), configuration.TrustedRoots...)}
}
func (f OSFileSystem) store(path string, owner *Ownership) securefs.Store {
	root := ""
	if len(f.TrustedRoots) == 0 {
		root = string(filepath.Separator)
	}
	for _, candidate := range f.TrustedRoots {
		if pathWithin(path, candidate) && (root == "" || len(filepath.Clean(candidate)) > len(filepath.Clean(root))) {
			root = candidate
		}
	}
	var secureOwner *securefs.Owner
	if owner != nil {
		secureOwner = &securefs.Owner{UID: owner.UID, GID: owner.GID}
	}
	return securefs.Store{TrustedRoot: root, Owner: secureOwner}
}
func (f OSFileSystem) ReadFile(path string) ([]byte, error) { return f.store(path, nil).ReadFile(path) }
func (f OSFileSystem) Remove(path string) error             { return f.store(path, nil).Remove(path) }
func (f OSFileSystem) AtomicWrite(path string, data []byte, mode os.FileMode, owner *Ownership) error {
	return f.store(path, owner).AtomicWrite(path, data, mode)
}
func (f OSFileSystem) WithLock(path string, owner *Ownership, action func() error) error {
	return f.store(path, owner).WithLock(path, action)
}

type priorValue struct {
	Present bool            `json:"present"`
	Value   json.RawMessage `json:"value,omitempty"`
}
type recovery struct {
	ConfigPresent  bool                  `json:"configPresent"`
	ProxiesPresent bool                  `json:"proxiesPresent"`
	DefaultPresent bool                  `json:"defaultPresent"`
	Original       map[string]priorValue `json:"original"`
	Fingerprint    string                `json:"fingerprint"`
}

type Adapter struct {
	configuration Configuration
	files         FileSystem
}

var _ target.Target = (*Adapter)(nil)

func New(configuration Configuration, files FileSystem) *Adapter {
	if files == nil {
		configured := NewOSFileSystem(configuration)
		files = configured
	}
	return &Adapter{configuration: configuration, files: files}
}

func (a *Adapter) ID() string { return "docker-containers" }
func (a *Adapter) Description() target.Description {
	return target.Description{
		Name:    "Docker containers/builds",
		Summary: "Sets proxy defaults injected into future Docker containers and builds.",
		Details: "Affects new containers and builds through the owning user's Docker client configuration; it does not affect existing containers and is not Docker daemon registry access. It requires write access to the user's Docker configuration and does not contact the daemon.",
	}
}
func (a *Adapter) Confirmation(bool) string { return "" }

func (a *Adapter) Availability(context.Context) target.Availability {
	if !a.usablePath(a.configuration.ConfigFile) || !a.usablePath(a.configuration.RecoveryFile) {
		return target.Availability{Evidence: "standard Docker client configuration paths are not usable for the owning user"}
	}
	return target.Availability{Available: true, Evidence: "standard Docker client configuration is available for the owning user"}
}

func (a *Adapter) usablePath(path string) bool {
	if !filepath.IsAbs(path) {
		return false
	}
	if len(a.configuration.TrustedRoots) == 0 {
		return true
	}
	for _, root := range a.configuration.TrustedRoots {
		if filepath.IsAbs(root) && pathWithin(path, root) && filepath.Clean(path) != filepath.Clean(root) {
			return true
		}
	}
	return false
}
func (a *Adapter) ConfigPath() string   { return a.configuration.ConfigFile }
func (a *Adapter) RecoveryPath() string { return a.configuration.RecoveryFile }
func (a *Adapter) LockPath() string     { return a.configuration.RecoveryFile + ".lock" }

func (a *Adapter) Inspect(_ context.Context, active *profile.Profile) target.Inspection {
	metadata, managed, metadataErr := a.readRecovery()
	config, _, configErr := a.readConfig()
	if managed || (metadataErr != nil && !errors.Is(metadataErr, fs.ErrNotExist)) {
		if metadataErr != nil {
			return target.Inspection{State: target.Drifted, Evidence: "managed Docker client recovery metadata cannot be read"}
		}
		if configErr != nil {
			return target.Inspection{State: target.Drifted, Evidence: "managed Docker client configuration is missing, unreadable, or not safely mergeable"}
		}
		desired, desiredErr := desiredDefaults(active)
		if desiredErr == nil && fingerprintCurrent(config) == metadata.Fingerprint && fingerprintDefaults(desired) == metadata.Fingerprint {
			return target.Inspection{State: target.Enabled, Evidence: "managed Docker client proxy defaults match the Active Profile"}
		}
		return target.Inspection{State: target.Drifted, Evidence: "managed Docker client proxy defaults do not match the Active Profile"}
	}
	if configErr == nil && recognizesProxyDefaults(config) {
		return target.Inspection{State: target.External, Evidence: "recognized proxy defaults exist in Docker client config.json"}
	}
	return target.Inspection{State: target.Disabled, Evidence: "no recognized Docker client proxy defaults detected"}
}

func (a *Adapter) SetDesired(ctx context.Context, enabled bool, active *profile.Profile) target.OperationResult {
	if !a.Availability(ctx).Available {
		return target.OperationResult{Inspection: a.Inspect(ctx, active), Err: errors.New("Docker containers/builds Target is unavailable: standard Docker client configuration cannot be used")}
	}
	if enabled && active == nil {
		return target.OperationResult{Inspection: a.Inspect(ctx, active), Err: errors.New("no Active Profile; open Profile management to create and activate one")}
	}

	var inspection target.Inspection
	err := a.files.WithLock(a.LockPath(), a.ownership(), func() error {
		if enabled {
			inspection = a.Inspect(ctx, active)
			if inspection.State == target.Enabled {
				return nil
			}
			if err := a.enable(active); err != nil {
				inspection = a.Inspect(ctx, active)
				return err
			}
		} else if err := a.disable(); err != nil {
			inspection = a.Inspect(ctx, active)
			return err
		}
		inspection = a.Inspect(ctx, active)
		return nil
	})
	if err != nil {
		if inspection.Evidence == "" {
			inspection = a.Inspect(ctx, active)
		}
		err = redactError(err, active)
	}
	return target.OperationResult{Inspection: inspection, Err: err}
}

func (a *Adapter) enable(active *profile.Profile) error {
	desired, err := desiredDefaults(active)
	if err != nil {
		return err
	}
	config, configPresent, err := a.readConfig()
	if err != nil {
		return fmt.Errorf("read Docker client configuration for safe JSON merge: %w", err)
	}
	metadata, managed, recoveryErr := a.readRecovery()
	if recoveryErr != nil && !errors.Is(recoveryErr, fs.ErrNotExist) {
		return fmt.Errorf("read Docker client recovery metadata: %w", recoveryErr)
	}
	proxies, proxiesPresent, err := childObject(config, "proxies")
	if err != nil {
		return err
	}
	defaults, defaultPresent, err := childObject(proxies, "default")
	if err != nil {
		return err
	}
	if !managed {
		metadata = recovery{ConfigPresent: configPresent, ProxiesPresent: proxiesPresent, DefaultPresent: defaultPresent, Original: make(map[string]priorValue)}
		for _, key := range managedKeys {
			value, present := defaults[key]
			metadata.Original[key] = priorValue{Present: present, Value: cloneRaw(value)}
		}
	}
	metadata.Fingerprint = fingerprintDefaults(desired)
	metadataData, err := json.MarshalIndent(metadata, "", "  ")
	if err != nil {
		return err
	}
	if err := a.writeOwned(a.configuration.RecoveryFile, append(metadataData, '\n')); err != nil {
		return fmt.Errorf("persist Docker client recovery metadata before changing proxy defaults: %w", err)
	}
	applyDesired(defaults, desired)
	setChildObject(proxies, "default", defaults)
	setChildObject(config, "proxies", proxies)
	if err := a.writeConfig(config); err != nil {
		return fmt.Errorf("write Docker client proxy defaults after recovery metadata persisted: %w", err)
	}
	return nil
}

func (a *Adapter) disable() error {
	metadata, managed, err := a.readRecovery()
	if errors.Is(err, fs.ErrNotExist) || !managed {
		return nil
	}
	if err != nil {
		return fmt.Errorf("read Docker client recovery metadata: %w", err)
	}
	config, configPresent, err := a.readConfig()
	if err != nil && !errors.Is(err, fs.ErrNotExist) {
		return fmt.Errorf("read Docker client configuration for restoration: %w", err)
	}
	if !configPresent {
		config = make(map[string]json.RawMessage)
	}
	proxies, _, err := childObject(config, "proxies")
	if err != nil {
		return err
	}
	defaults, _, err := childObject(proxies, "default")
	if err != nil {
		return err
	}
	for _, key := range managedKeys {
		prior := metadata.Original[key]
		if prior.Present {
			defaults[key] = cloneRaw(prior.Value)
		} else {
			delete(defaults, key)
		}
	}
	if len(defaults) == 0 && !metadata.DefaultPresent {
		delete(proxies, "default")
	} else {
		setChildObject(proxies, "default", defaults)
	}
	if len(proxies) == 0 && !metadata.ProxiesPresent {
		delete(config, "proxies")
	} else {
		setChildObject(config, "proxies", proxies)
	}
	if len(config) == 0 && !metadata.ConfigPresent {
		if err := a.files.Remove(a.configuration.ConfigFile); err != nil && !errors.Is(err, fs.ErrNotExist) {
			return fmt.Errorf("remove newly created empty Docker client configuration: %w", err)
		}
	} else if err := a.writeConfig(config); err != nil {
		return fmt.Errorf("restore prior Docker client proxy defaults: %w", err)
	}
	if err := a.files.Remove(a.configuration.RecoveryFile); err != nil && !errors.Is(err, fs.ErrNotExist) {
		return fmt.Errorf("remove Docker client recovery metadata after restoration: %w", err)
	}
	return nil
}

func desiredDefaults(active *profile.Profile) (map[string]string, error) {
	if active == nil {
		return nil, errors.New("Active Profile is required")
	}
	normalized, err := profile.ValidateAndNormalize(*active)
	if err != nil {
		return nil, err
	}
	for field, raw := range map[string]string{"HTTP proxy": normalized.HTTPURL, "HTTPS proxy": normalized.HTTPSURL} {
		if raw == "" {
			continue
		}
		parsed, _ := url.Parse(raw)
		if parsed.Scheme != "http" && parsed.Scheme != "https" {
			return nil, fmt.Errorf("%s scheme %s cannot be represented by Docker's documented %sProxy default", field, parsed.Scheme, strings.ToLower(strings.Fields(field)[0]))
		}
	}
	return map[string]string{
		"httpProxy":  normalized.HTTPURL,
		"httpsProxy": normalized.HTTPSURL,
		"allProxy":   normalized.AllURL,
		"noProxy":    strings.Join(normalized.Bypass, ","),
	}, nil
}

func (a *Adapter) readRecovery() (recovery, bool, error) {
	data, err := a.files.ReadFile(a.configuration.RecoveryFile)
	if err != nil {
		return recovery{}, false, err
	}
	var value recovery
	if err := json.Unmarshal(data, &value); err != nil {
		return recovery{}, true, err
	}
	if value.Original == nil {
		return recovery{}, true, errors.New("Docker client recovery metadata is incomplete")
	}
	fingerprintBytes, fingerprintErr := hex.DecodeString(value.Fingerprint)
	if fingerprintErr != nil || len(fingerprintBytes) != sha256.Size {
		return recovery{}, true, errors.New("Docker client recovery metadata has an invalid fingerprint")
	}
	for _, key := range managedKeys {
		prior, present := value.Original[key]
		if !present || (prior.Present && !json.Valid(prior.Value)) {
			return recovery{}, true, errors.New("Docker client recovery metadata is incomplete")
		}
	}
	return value, true, nil
}

func (a *Adapter) readConfig() (map[string]json.RawMessage, bool, error) {
	data, err := a.files.ReadFile(a.configuration.ConfigFile)
	if errors.Is(err, fs.ErrNotExist) {
		return make(map[string]json.RawMessage), false, nil
	}
	if err != nil {
		return nil, false, err
	}
	object, err := decodeObject(data, "Docker client configuration")
	return object, true, err
}

func decodeObject(data []byte, description string) (map[string]json.RawMessage, error) {
	var object map[string]json.RawMessage
	if err := json.Unmarshal(data, &object); err != nil {
		return nil, fmt.Errorf("parse %s: %w", description, err)
	}
	if object == nil {
		return nil, fmt.Errorf("%s must be a JSON object", description)
	}
	return object, nil
}
func childObject(parent map[string]json.RawMessage, key string) (map[string]json.RawMessage, bool, error) {
	raw, present := parent[key]
	if !present {
		return make(map[string]json.RawMessage), false, nil
	}
	object, err := decodeObject(raw, "Docker client "+key+" setting")
	return object, true, err
}
func setChildObject(parent map[string]json.RawMessage, key string, child map[string]json.RawMessage) {
	data, _ := json.Marshal(child)
	parent[key] = data
}
func applyDesired(defaults map[string]json.RawMessage, desired map[string]string) {
	for _, key := range managedKeys {
		if value := desired[key]; value != "" {
			data, _ := json.Marshal(value)
			defaults[key] = data
		} else {
			delete(defaults, key)
		}
	}
}
func recognizesProxyDefaults(config map[string]json.RawMessage) bool {
	proxies, _, err := childObject(config, "proxies")
	if err != nil {
		return false
	}
	defaults, _, err := childObject(proxies, "default")
	if err != nil {
		return false
	}
	for _, key := range append(append([]string(nil), managedKeys...), "ftpProxy") {
		var value string
		if raw, ok := defaults[key]; ok && json.Unmarshal(raw, &value) == nil && value != "" {
			return true
		}
	}
	return false
}

type managedValue struct {
	Present bool   `json:"present"`
	Valid   bool   `json:"valid"`
	Value   string `json:"value,omitempty"`
}

func fingerprintDefaults(values map[string]string) string {
	snapshot := make(map[string]managedValue, len(managedKeys))
	for _, key := range managedKeys {
		if value := values[key]; value != "" {
			snapshot[key] = managedValue{Present: true, Valid: true, Value: value}
		} else {
			snapshot[key] = managedValue{}
		}
	}
	return fingerprintSnapshot(snapshot)
}

func fingerprintCurrent(config map[string]json.RawMessage) string {
	snapshot := make(map[string]managedValue, len(managedKeys))
	proxies, _, proxyErr := childObject(config, "proxies")
	defaults, _, defaultErr := childObject(proxies, "default")
	for _, key := range managedKeys {
		raw, present := defaults[key]
		value := managedValue{Present: present}
		if present && proxyErr == nil && defaultErr == nil && json.Unmarshal(raw, &value.Value) == nil {
			value.Valid = true
		}
		snapshot[key] = value
	}
	return fingerprintSnapshot(snapshot)
}

func fingerprintSnapshot(snapshot map[string]managedValue) string {
	data, _ := json.Marshal(snapshot)
	sum := sha256.Sum256(data)
	return hex.EncodeToString(sum[:])
}
func cloneRaw(value json.RawMessage) json.RawMessage { return append(json.RawMessage(nil), value...) }
func (a *Adapter) ownership() *Ownership {
	if !a.configuration.OwnFiles {
		return nil
	}
	return &Ownership{UID: a.configuration.UID, GID: a.configuration.GID}
}
func (a *Adapter) writeOwned(path string, data []byte) error {
	return a.files.AtomicWrite(path, data, 0o600, a.ownership())
}
func (a *Adapter) writeConfig(config map[string]json.RawMessage) error {
	data, err := json.MarshalIndent(config, "", "  ")
	if err != nil {
		return err
	}
	return a.writeOwned(a.configuration.ConfigFile, append(data, '\n'))
}

type redactedError struct {
	message string
	class   error
}

func (e *redactedError) Error() string       { return e.message }
func (e *redactedError) Is(other error) bool { return e.class != nil && errors.Is(e.class, other) }
func redactError(err error, active *profile.Profile) error {
	message := profile.RedactText(err.Error())
	if active != nil {
		for _, raw := range []string{active.SingleURL, active.HTTPURL, active.HTTPSURL, active.AllURL} {
			if raw != "" {
				message = strings.ReplaceAll(message, raw, profile.ObscureURL(raw))
			}
		}
	}
	var class error
	for _, safe := range []error{os.ErrPermission, fs.ErrNotExist, fs.ErrExist, context.Canceled, context.DeadlineExceeded} {
		if errors.Is(err, safe) {
			class = safe
			break
		}
	}
	return &redactedError{message: message, class: class}
}