/*
Copyright © The ESO 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

    https://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 gitlab implements a GitLab provider for External Secrets.
package gitlab

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"sort"
	"strconv"
	"strings"

	"github.com/tidwall/gjson"
	gitlab "gitlab.com/gitlab-org/api/client-go"
	corev1 "k8s.io/api/core/v1"
	ctrl "sigs.k8s.io/controller-runtime"

	esv1 "github.com/external-secrets/external-secrets/apis/externalsecrets/v1"
	"github.com/external-secrets/external-secrets/runtime/constants"
	"github.com/external-secrets/external-secrets/runtime/esutils"
	"github.com/external-secrets/external-secrets/runtime/esutils/resolvers"
	"github.com/external-secrets/external-secrets/runtime/find"
	"github.com/external-secrets/external-secrets/runtime/metrics"
)

const (
	errList                         = "could not verify whether the gitlabClient is valid: %w"
	errProjectAuth                  = "gitlabClient is not allowed to get secrets for project id [%s]"
	errGroupAuth                    = "gitlabClient is not allowed to get secrets for group id [%s]"
	errUninitializedGitlabProvider  = "provider gitlab is not initialized"
	errNameNotDefined               = "'find.name' is mandatory"
	errEnvironmentIsConstricted     = "'find.tags' is constrained by 'environment_scope' of the store"
	errTagsOnlyEnvironmentSupported = "'find.tags' only supports 'environment_scope'"
	errPathNotImplemented           = "'find.path' is not implemented in the GitLab provider"
	errJSONSecretUnmarshal          = "unable to unmarshal secret from JSON: %w"
	errNotImplemented               = "not implemented"
)

// https://github.com/external-secrets/external-secrets/issues/644
var _ esv1.SecretsClient = &gitlabBase{}
var _ esv1.Provider = &Provider{}

// ProjectsClient is an interface for interacting with GitLab project APIs.
type ProjectsClient interface {
	ListProjectsGroups(pid any, opt *gitlab.ListProjectGroupOptions, options ...gitlab.RequestOptionFunc) ([]*gitlab.ProjectGroup, *gitlab.Response, error)
}

// ProjectVariablesClient is an interface for managing GitLab project variables.
type ProjectVariablesClient interface {
	GetVariable(pid any, key string, opt *gitlab.GetProjectVariableOptions, options ...gitlab.RequestOptionFunc) (*gitlab.ProjectVariable, *gitlab.Response, error)
	ListVariables(pid any, opt *gitlab.ListProjectVariablesOptions, options ...gitlab.RequestOptionFunc) ([]*gitlab.ProjectVariable, *gitlab.Response, error)
}

// GroupVariablesClient is an interface for managing GitLab group variables.
type GroupVariablesClient interface {
	GetVariable(gid any, key string, opts *gitlab.GetGroupVariableOptions, options ...gitlab.RequestOptionFunc) (*gitlab.GroupVariable, *gitlab.Response, error)
	ListVariables(gid any, opt *gitlab.ListGroupVariablesOptions, options ...gitlab.RequestOptionFunc) ([]*gitlab.GroupVariable, *gitlab.Response, error)
}

// ProjectGroupPathSorter implements sort.Interface for sorting project groups by path length.
type ProjectGroupPathSorter []*gitlab.ProjectGroup

func (a ProjectGroupPathSorter) Len() int           { return len(a) }
func (a ProjectGroupPathSorter) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ProjectGroupPathSorter) Less(i, j int) bool { return len(a[i].FullPath) < len(a[j].FullPath) }

var log = ctrl.Log.WithName("provider").WithName("gitlab")

// Set gitlabBase credentials to Access Token.
func (g *gitlabBase) getAuth(ctx context.Context) (string, error) {
	return resolvers.SecretKeyRef(
		ctx,
		g.kube,
		g.storeKind,
		g.namespace,
		&g.store.Auth.SecretRef.AccessToken)
}

func (g *gitlabBase) DeleteSecret(_ context.Context, _ esv1.PushSecretRemoteRef) error {
	return errors.New(errNotImplemented)
}

func (g *gitlabBase) SecretExists(_ context.Context, _ esv1.PushSecretRemoteRef) (bool, error) {
	return false, errors.New(errNotImplemented)
}

func (g *gitlabBase) PushSecret(_ context.Context, _ *corev1.Secret, _ esv1.PushSecretData) error {
	return errors.New(errNotImplemented)
}

// GetAllSecrets syncs all gitlab project and group variables into a single Kubernetes Secret.
func (g *gitlabBase) GetAllSecrets(_ context.Context, ref esv1.ExternalSecretFind) (map[string][]byte, error) {
	if esutils.IsNil(g.projectVariablesClient) {
		return nil, errors.New(errUninitializedGitlabProvider)
	}
	var effectiveEnvironment = g.store.Environment
	if ref.Tags != nil {
		environment, err := ExtractTag(ref.Tags)
		if err != nil {
			return nil, err
		}
		if !isEmptyOrWildcard(effectiveEnvironment) && !isEmptyOrWildcard(environment) {
			return nil, errors.New(errEnvironmentIsConstricted)
		}
		effectiveEnvironment = environment
	}
	if ref.Path != nil {
		return nil, errors.New(errPathNotImplemented)
	}
	if ref.Name == nil {
		return nil, errors.New(errNameNotDefined)
	}

	var matcher *find.Matcher
	if ref.Name != nil {
		m, err := find.New(*ref.Name)
		if err != nil {
			return nil, err
		}
		matcher = m
	}

	err := g.ResolveGroupIDs()
	if err != nil {
		return nil, err
	}

	secretData, err := g.fetchSecretData(effectiveEnvironment, matcher)
	if err != nil {
		return nil, err
	}

	// _Note_: fetchProjectVariables alters secret data map
	if err := g.fetchProjectVariables(effectiveEnvironment, matcher, secretData); err != nil {
		return nil, err
	}

	return secretData, nil
}

func (g *gitlabBase) fetchProjectVariables(effectiveEnvironment string, matcher *find.Matcher, secretData map[string][]byte) error {
	var popts = &gitlab.ListProjectVariablesOptions{PerPage: 100}
	nonWildcardSet := make(map[string]bool)
	for projectPage := 1; ; projectPage++ {
		popts.Page = projectPage
		projectData, response, err := g.projectVariablesClient.ListVariables(g.store.ProjectID, popts)
		metrics.ObserveAPICall(constants.ProviderGitLab, constants.CallGitLabProjectListVariables, err)
		if err != nil {
			return err
		}

		processProjectVariables(projectData, effectiveEnvironment, matcher, secretData, nonWildcardSet)
		if response.CurrentPage >= response.TotalPages {
			break
		}
	}

	return nil
}

func processProjectVariables(
	projectData []*gitlab.ProjectVariable,
	effectiveEnvironment string,
	matcher *find.Matcher,
	secretData map[string][]byte,
	nonWildcardSet map[string]bool,
) {
	for _, data := range projectData {
		matching, key, isWildcard := matchesFilter(effectiveEnvironment, data.EnvironmentScope, data.Key, matcher)
		if !matching {
			continue
		}
		if isWildcard && nonWildcardSet[key] {
			continue
		}
		secretData[key] = []byte(data.Value)
		if !isWildcard {
			nonWildcardSet[key] = true
		}
	}
}

func (g *gitlabBase) fetchSecretData(effectiveEnvironment string, matcher *find.Matcher) (map[string][]byte, error) {
	var gopts = &gitlab.ListGroupVariablesOptions{PerPage: 100}
	secretData := make(map[string][]byte)
	for _, groupID := range g.store.GroupIDs {
		if err := g.setVariablesForGroupID(effectiveEnvironment, matcher, gopts, groupID, secretData); err != nil {
			return nil, err
		}
	}

	return secretData, nil
}

func (g *gitlabBase) setVariablesForGroupID(
	effectiveEnvironment string,
	matcher *find.Matcher,
	gopts *gitlab.ListGroupVariablesOptions,
	groupID string,
	secretData map[string][]byte,
) error {
	for groupPage := 1; ; groupPage++ {
		gopts.Page = groupPage
		groupVars, response, err := g.groupVariablesClient.ListVariables(groupID, gopts)
		metrics.ObserveAPICall(constants.ProviderGitLab, constants.CallGitLabGroupListVariables, err)
		if err != nil {
			return err
		}
		g.setGroupValues(effectiveEnvironment, matcher, groupVars, secretData)

		if response.CurrentPage >= response.TotalPages {
			break
		}
	}
	return nil
}

func (g *gitlabBase) setGroupValues(
	effectiveEnvironment string,
	matcher *find.Matcher,
	groupVars []*gitlab.GroupVariable,
	secretData map[string][]byte,
) {
	for _, data := range groupVars {
		matching, key, isWildcard := matchesFilter(effectiveEnvironment, data.EnvironmentScope, data.Key, matcher)
		if !matching {
			continue
		}
		// Check if a more specific variable already exists (project environment > project variable > group environment > group variable)
		_, exists := secretData[key]
		if exists && isWildcard {
			continue
		}
		secretData[key] = []byte(data.Value)
	}
}

// ExtractTag extracts the environment scope from the provided tags map.
func ExtractTag(tags map[string]string) (string, error) {
	var environmentScope string
	for tag, value := range tags {
		if tag != "environment_scope" {
			return "", errors.New(errTagsOnlyEnvironmentSupported)
		}
		environmentScope = value
	}
	return environmentScope, nil
}

func (g *gitlabBase) getGroupVariables(groupID string, ref esv1.ExternalSecretDataRemoteRef, gopts *gitlab.GetGroupVariableOptions) (*gitlab.GroupVariable, *gitlab.Response, error) {
	groupVar, resp, err := g.groupVariablesClient.GetVariable(groupID, ref.Key, gopts)
	metrics.ObserveAPICall(constants.ProviderGitLab, constants.CallGitLabGroupGetVariable, err)
	if err != nil {
		if resp != nil && resp.StatusCode == http.StatusNotFound && !isEmptyOrWildcard(g.store.Environment) {
			if gopts == nil {
				gopts = &gitlab.GetGroupVariableOptions{}
			}
			if gopts.Filter == nil {
				gopts.Filter = &gitlab.VariableFilter{}
			}
			gopts.Filter.EnvironmentScope = "*"
			groupVar, resp, err = g.groupVariablesClient.GetVariable(groupID, ref.Key, gopts)
			metrics.ObserveAPICall(constants.ProviderGitLab, constants.CallGitLabGroupGetVariable, err)
			if err != nil || resp == nil {
				return nil, resp, fmt.Errorf("error getting group variable %s from GitLab: %w", ref.Key, err)
			}
		} else {
			return nil, resp, err
		}
	}

	return groupVar, resp, nil
}

func (g *gitlabBase) GetSecret(_ context.Context, ref esv1.ExternalSecretDataRemoteRef) ([]byte, error) {
	if esutils.IsNil(g.projectVariablesClient) || esutils.IsNil(g.groupVariablesClient) {
		return nil, errors.New(errUninitializedGitlabProvider)
	}

	// Need to replace hyphens with underscores to work with GitLab API
	ref.Key = strings.ReplaceAll(ref.Key, "-", "_")
	// Retrieves a gitlab variable in the form
	// {
	// 	"key": "TEST_VARIABLE_1",
	// 	"variable_type": "env_var",
	// 	"value": "TEST_1",
	// 	"protected": false,
	// 	"masked": true,
	// 	"environment_scope": "*"
	// }
	var gopts *gitlab.GetGroupVariableOptions
	var vopts *gitlab.GetProjectVariableOptions
	if g.store.Environment != "" {
		gopts = &gitlab.GetGroupVariableOptions{Filter: &gitlab.VariableFilter{EnvironmentScope: g.store.Environment}}
		vopts = &gitlab.GetProjectVariableOptions{Filter: &gitlab.VariableFilter{EnvironmentScope: g.store.Environment}}
	}

	data, err := g.getVariables(ref, vopts)
	if err == nil {
		return extractVariable(ref, data.Value)
	}

	// If project variable not found, try group variables
	if errors.Is(err, gitlab.ErrNotFound) {
		return g.tryGroupVariables(ref, gopts, err)
	}

	return nil, err
}

// tryGroupVariables attempts to retrieve the secret from group variables when project lookup fails.
func (g *gitlabBase) tryGroupVariables(ref esv1.ExternalSecretDataRemoteRef, gopts *gitlab.GetGroupVariableOptions, originalErr error) ([]byte, error) {
	// Load groupIds from the `InheritFromGroups` property
	if err := g.ResolveGroupIDs(); err != nil {
		return nil, err
	}

	for i := len(g.store.GroupIDs) - 1; i >= 0; i-- {
		groupID := g.store.GroupIDs[i]
		groupVar, _, err := g.getGroupVariables(groupID, ref, gopts)
		if err == nil {
			return extractVariable(ref, groupVar.Value)
		}

		// If a 404 error, continue to the next stage, otherwise exit early with error
		if errors.Is(err, gitlab.ErrNotFound) {
			continue
		}
		return nil, err
	}

	// No group variables found, return the original project error
	return nil, originalErr
}

func extractVariable(ref esv1.ExternalSecretDataRemoteRef, value string) ([]byte, error) {
	// If no property specified, return the raw value
	if ref.Property == "" {
		if value == "" {
			return nil, fmt.Errorf("invalid secret received. no secret string for key: %s", ref.Key)
		}
		return []byte(value), nil
	}

	// Extract property from JSON value
	val := gjson.Get(value, ref.Property)
	if !val.Exists() {
		return nil, fmt.Errorf("key %s does not exist in secret %s", ref.Property, ref.Key)
	}
	return []byte(val.String()), nil
}

func (g *gitlabBase) GetSecretMap(ctx context.Context, ref esv1.ExternalSecretDataRemoteRef) (map[string][]byte, error) {
	// Gets a secret as normal, expecting secret value to be a json object
	data, err := g.GetSecret(ctx, ref)
	if err != nil {
		return nil, fmt.Errorf("error getting secret %s: %w", ref.Key, err)
	}

	// Maps the json data to a string:string map
	kv := make(map[string]string)
	err = json.Unmarshal(data, &kv)
	if err != nil {
		return nil, fmt.Errorf(errJSONSecretUnmarshal, err)
	}

	// Converts values in K:V pairs into bytes, while leaving keys as strings
	secretData := make(map[string][]byte)
	for k, v := range kv {
		secretData[k] = []byte(v)
	}
	return secretData, nil
}

func isEmptyOrWildcard(environment string) bool {
	return environment == "" || environment == "*"
}

func matchesFilter(environment, varEnvironment, key string, matcher *find.Matcher) (bool, string, bool) {
	isWildcard := isEmptyOrWildcard(varEnvironment)
	if !isWildcard && !isEmptyOrWildcard(environment) {
		// as of now gitlab does not support filtering of EnvironmentScope through the api call
		if varEnvironment != environment {
			return false, "", isWildcard
		}
	}

	if key == "" || (matcher != nil && !matcher.MatchName(key)) {
		return false, "", isWildcard
	}

	return true, key, isWildcard
}

func (g *gitlabBase) Close(_ context.Context) error {
	return nil
}

func (g *gitlabBase) ResolveGroupIDs() error {
	if g.store.InheritFromGroups {
		projectGroups, resp, err := g.projectsClient.ListProjectsGroups(g.store.ProjectID, nil)
		metrics.ObserveAPICall(constants.ProviderGitLab, constants.CallGitLabListProjectsGroups, err)
		if resp.StatusCode >= 400 && err != nil {
			return err
		}
		sort.Sort(ProjectGroupPathSorter(projectGroups))
		discoveredIDs := make([]string, len(projectGroups))
		for i, group := range projectGroups {
			discoveredIDs[i] = strconv.Itoa(group.ID)
		}
		g.store.GroupIDs = discoveredIDs
	}
	return nil
}

// Validate will use the gitlab projectVariablesClient/groupVariablesClient to validate the gitlab provider using the ListVariable call to ensure get permissions without needing a specific key.
func (g *gitlabBase) Validate() (esv1.ValidationResult, error) {
	if g.store.ProjectID != "" {
		_, resp, err := g.projectVariablesClient.ListVariables(g.store.ProjectID, nil)
		metrics.ObserveAPICall(constants.ProviderGitLab, constants.CallGitLabProjectListVariables, err)
		if err != nil {
			return esv1.ValidationResultError, fmt.Errorf(errList, err)
		} else if resp == nil || resp.StatusCode != http.StatusOK {
			return esv1.ValidationResultError, fmt.Errorf(errProjectAuth, g.store.ProjectID)
		}

		err = g.ResolveGroupIDs()
		if err != nil {
			return esv1.ValidationResultError, fmt.Errorf(errList, err)
		}
		log.V(1).Info("discovered project groups", "name", g.store.GroupIDs)
	}

	if len(g.store.GroupIDs) > 0 {
		for _, groupID := range g.store.GroupIDs {
			_, resp, err := g.groupVariablesClient.ListVariables(groupID, nil)
			metrics.ObserveAPICall(constants.ProviderGitLab, constants.CallGitLabGroupListVariables, err)
			if err != nil {
				return esv1.ValidationResultError, fmt.Errorf(errList, err)
			} else if resp == nil || resp.StatusCode != http.StatusOK {
				return esv1.ValidationResultError, fmt.Errorf(errGroupAuth, groupID)
			}
		}
	}

	return esv1.ValidationResultReady, nil
}
