/*
Copyright 2026.

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 instance validates PostgreSQLInstance dependencies and initializes
// the controller registry without exposing administrative credentials.
package instance

import (
	"context"
	"errors"
	"net"
	"net/url"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
	kubernetesauth "github.com/openbao/openbao/api/auth/kubernetes/v2"
	openbao "github.com/openbao/openbao/api/v2"
	"k8s.io/apimachinery/pkg/util/validation"

	databasev1alpha1 "git.ddupan.top/panxiao81/postgresql-tenant-operator/api/v1alpha1"
	"git.ddupan.top/panxiao81/postgresql-tenant-operator/internal/postgresql/registry"
)

// Config contains the deployment-level settings needed by Instance readiness.
type Config struct {
	OpenBaoAddress          string
	OpenBaoConsumerAddress  string
	OpenBaoAuthMount        string
	OpenBaoAuthRole         string
	ServiceAccountTokenPath string
	OpenBaoKVMount          string
	OpenBaoTenantBasePath   string
	ExternalSecretStoreName string
	PostgreSQLCABundlePath  string
	Timeout                 time.Duration
}

// Initializer implements the Instance validation and registry phases.
type Initializer struct{ config Config }

type failure struct {
	reason  string
	message string
}

func (e failure) Error() string           { return e.message }
func (e failure) ConditionReason() string { return e.reason }

func dependencyFailure(message string) error {
	return failure{reason: databasev1alpha1.ReasonDependencyUnavailable, message: message}
}

func authenticationFailure(message string) error {
	return failure{reason: databasev1alpha1.ReasonAuthenticationFailed, message: message}
}

func privilegeFailure(message string) error {
	return failure{reason: databasev1alpha1.ReasonInsufficientPrivileges, message: message}
}

// New validates config and constructs an Initializer.
func New(config Config) (*Initializer, error) {
	if config.OpenBaoAddress == "" || config.OpenBaoAuthRole == "" || config.OpenBaoAuthMount == "" ||
		config.ServiceAccountTokenPath == "" || config.OpenBaoKVMount == "" || config.OpenBaoTenantBasePath == "" ||
		config.ExternalSecretStoreName == "" || config.Timeout <= 0 {
		return nil, errors.New("initialize instance dependencies: required configuration is missing")
	}
	if err := validateAddress(config.OpenBaoAddress); err != nil {
		return nil, err
	}
	if config.OpenBaoConsumerAddress == "" {
		config.OpenBaoConsumerAddress = config.OpenBaoAddress
	}
	if err := validateAddress(config.OpenBaoConsumerAddress); err != nil {
		return nil, err
	}
	if !filepath.IsAbs(config.ServiceAccountTokenPath) || validateRelativePath(config.OpenBaoAuthMount, false) != nil ||
		validateRelativePath(config.OpenBaoKVMount, false) != nil || validateRelativePath(config.OpenBaoTenantBasePath, true) != nil ||
		len(validation.IsDNS1123Subdomain(config.ExternalSecretStoreName)) != 0 {
		return nil, errors.New("initialize instance dependencies: invalid path or resource name configuration")
	}
	return &Initializer{config: config}, nil
}

// Validate authenticates to OpenBao, reads the administrative credential, and
// verifies that PostgreSQL accepts it. It returns only public server metadata.
func (i *Initializer) Validate(ctx context.Context, instance *databasev1alpha1.PostgreSQLInstance) (string, error) {
	pool, err := i.connect(ctx, instance)
	if err != nil {
		return "", err
	}
	defer pool.Close()

	var version string
	if err := pool.QueryRow(ctx, "SHOW server_version").Scan(&version); err != nil {
		return "", errors.New("validate PostgreSQL server metadata")
	}
	return version, nil
}

// InitializeRegistry repeats dependency validation and applies registry migrations.
func (i *Initializer) InitializeRegistry(ctx context.Context, instance *databasev1alpha1.PostgreSQLInstance) (string, error) {
	pool, err := i.connect(ctx, instance)
	if err != nil {
		return "", err
	}
	defer pool.Close()

	if err := registry.NewStore(pool).Bootstrap(ctx); err != nil {
		return "", privilegeFailure("initialize PostgreSQL registry")
	}
	var version string
	if err := pool.QueryRow(ctx, "SHOW server_version").Scan(&version); err != nil {
		return "", errors.New("validate PostgreSQL server metadata")
	}
	return version, nil
}

func (i *Initializer) connect(ctx context.Context, instance *databasev1alpha1.PostgreSQLInstance) (*pgxpool.Pool, error) {
	if instance.Spec.Endpoint.SSLMode != databasev1alpha1.PostgreSQLSSLModeDisable && i.config.PostgreSQLCABundlePath == "" {
		return nil, errors.New("configure PostgreSQL TLS: CA bundle path is required")
	}
	ctx, cancel := context.WithTimeout(ctx, i.config.Timeout)
	defer cancel()

	clientConfig := openbao.DefaultConfig()
	clientConfig.Address = i.config.OpenBaoAddress
	clientConfig.Timeout = i.config.Timeout
	clientConfig.DisableEnvironment = true
	client, err := openbao.NewClient(clientConfig)
	if err != nil {
		return nil, dependencyFailure("create OpenBao client")
	}
	auth, err := kubernetesauth.NewKubernetesAuth(
		i.config.OpenBaoAuthRole,
		kubernetesauth.WithMountPath(i.config.OpenBaoAuthMount),
		kubernetesauth.WithServiceAccountTokenPath(i.config.ServiceAccountTokenPath),
	)
	if err != nil {
		return nil, errors.New("configure OpenBao Kubernetes authentication")
	}
	if secret, err := client.Auth().Login(ctx, auth); err != nil || secret == nil || secret.Auth == nil {
		return nil, authenticationFailure("authenticate to OpenBao")
	}

	secret, err := client.KVv2(i.config.OpenBaoKVMount).Get(ctx, instance.Spec.AdminCredentialRef.Path)
	if err != nil {
		return nil, privilegeFailure("read PostgreSQL administrative credential")
	}
	username, usernameOK := secret.Data[instance.Spec.AdminCredentialRef.UsernameKey].(string)
	password, passwordOK := secret.Data[instance.Spec.AdminCredentialRef.PasswordKey].(string)
	if !usernameOK || !passwordOK || username == "" || password == "" {
		return nil, errors.New("read PostgreSQL administrative credential fields")
	}

	connectionURL := &url.URL{
		Scheme: "postgresql",
		User:   url.UserPassword(username, password),
		Host:   net.JoinHostPort(instance.Spec.Endpoint.Host, strconv.Itoa(int(instance.Spec.Endpoint.Port))),
		Path:   instance.Spec.Endpoint.Database,
	}
	query := connectionURL.Query()
	query.Set("sslmode", string(instance.Spec.Endpoint.SSLMode))
	if instance.Spec.Endpoint.SSLMode != databasev1alpha1.PostgreSQLSSLModeDisable {
		query.Set("sslrootcert", i.config.PostgreSQLCABundlePath)
	}
	connectionURL.RawQuery = query.Encode()
	poolConfig, err := pgxpool.ParseConfig(connectionURL.String())
	if err != nil {
		return nil, errors.New("configure PostgreSQL connection")
	}
	pool, err := pgxpool.NewWithConfig(ctx, poolConfig)
	if err != nil {
		return nil, errors.New("connect to PostgreSQL")
	}
	if err := pool.Ping(ctx); err != nil {
		pool.Close()
		return nil, authenticationFailure("authenticate to PostgreSQL")
	}
	return pool, nil
}

func validateAddress(value string) error {
	parsed, err := url.Parse(value)
	if err != nil || !parsed.IsAbs() || (parsed.Scheme != "http" && parsed.Scheme != "https") || parsed.Host == "" ||
		parsed.User != nil || parsed.RawQuery != "" || parsed.Fragment != "" {
		return errors.New("initialize instance dependencies: invalid OpenBao address")
	}
	return nil
}

func validateRelativePath(value string, rejectAPILayer bool) error {
	for index, segment := range strings.Split(value, "/") {
		if segment == "" || segment == "." || segment == ".." ||
			(rejectAPILayer && index == 0 && (segment == "data" || segment == "metadata")) {
			return errors.New("invalid mount-relative path")
		}
	}
	return nil
}