package cluster

import (
	"bytes"
	"crypto/sha256"
	"fmt"
	"sort"
	"strings"
	"text/template"

	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
	"github.com/zalando/postgres-operator/pkg/util"
	v1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

const (
	pgBouncerConfigFileName        = "pgbouncer.ini"
	poolerConfigChecksumAnnotation = "acid.zalan.do/pgbouncer-config-checksum"
)

// FIPS-friendly pgbouncer.ini. Differs from the stock Zalando image template:
// no logfile/pidfile (distroless logs to stdout), auth_type is configurable,
// and TLS cert lines are emitted only when spec.TLS is set (the FIPS image does
// not run the openssl cert-generation step that the Zalando entrypoint does).
const pgBouncerConfigTemplateText = `# Generated by postgres-operator. Do not edit.
[databases]
* = host={{ .DBHost }} port={{ .DBPort }} auth_user={{ .User }}
postgres = host={{ .DBHost }} port={{ .DBPort }} auth_user={{ .User }}

[pgbouncer]
pool_mode = {{ .Mode }}
listen_port = {{ .ListenPort }}
listen_addr = *
admin_users = {{ .User }}
{{- if .StatsUsers }}
stats_users = {{ .StatsUsers }}
{{- end }}
auth_dbname = postgres
auth_file = /etc/pgbouncer/userlist.txt
auth_query = SELECT * FROM {{ .Schema }}.user_lookup($1)
auth_type = {{ .AuthType }}
server_tls_sslmode = require
{{- if .TLS }}
{{- if .TLSCAFile }}
server_tls_ca_file = {{ .TLSCAFile }}
{{- end }}
client_tls_sslmode = require
client_tls_key_file = {{ .TLSKeyFile }}
client_tls_cert_file = {{ .TLSCertFile }}
{{- end }}
log_connections = 0
log_disconnections = 0
max_prepared_statements = 200
default_pool_size = {{ .DefaultPoolSize }}
reserve_pool_size = {{ .ReservePoolSize }}
max_client_conn = {{ .MaxClientConn }}
max_db_connections = {{ .MaxDBConnections }}
idle_transaction_timeout = 600
server_login_retry = 5
ignore_startup_parameters = extra_float_digits,options
`

var pgBouncerConfigTemplate = template.Must(
	template.New(pgBouncerConfigFileName).Parse(pgBouncerConfigTemplateText))

type pgBouncerConfigParams struct {
	DBHost           string
	DBPort           int32
	ListenPort       int32
	User             string
	Schema           string
	Mode             string
	AuthType         string
	StatsUsers       string
	DefaultPoolSize  int32
	ReservePoolSize  int32
	MaxClientConn    int32
	MaxDBConnections int32
	TLS              bool
	TLSCAFile        string
	TLSKeyFile       string
	TLSCertFile      string
}

// generatePgBouncerIni renders the pgbouncer.ini for the given role from the
// cluster spec and operator config.
func (c *Cluster) generatePgBouncerIni(role PostgresRole) (string, error) {
	spec := &c.Spec
	connectionPoolerSpec := spec.ConnectionPooler
	if connectionPoolerSpec == nil {
		connectionPoolerSpec = &acidv1.ConnectionPooler{}
	}

	sizes := c.connectionPoolerSizes()

	infraRolesList := make([]string, 0)
	for infraRoleName := range c.InfrastructureRoles {
		infraRolesList = append(infraRolesList, infraRoleName)
	}
	sort.Strings(infraRolesList) // deterministic output for stable checksums

	params := pgBouncerConfigParams{
		DBHost:           c.serviceAddress(role),
		DBPort:           c.servicePort(role),
		ListenPort:       pgPort,
		User:             util.Coalesce(connectionPoolerSpec.User, c.OpConfig.ConnectionPooler.User),
		Schema:           util.Coalesce(connectionPoolerSpec.Schema, c.OpConfig.ConnectionPooler.Schema),
		Mode:             util.Coalesce(connectionPoolerSpec.Mode, c.OpConfig.ConnectionPooler.Mode),
		AuthType:         c.OpConfig.ConnectionPooler.AuthType,
		StatsUsers:       strings.Join(infraRolesList, ","),
		DefaultPoolSize:  sizes.defaultSize,
		ReservePoolSize:  sizes.reserveSize,
		MaxClientConn:    sizes.maxClientConn,
		MaxDBConnections: sizes.maxDBConn,
	}

	if spec.TLS != nil && spec.TLS.SecretName != "" {
		mountPath := "/tls"
		params.TLS = true
		params.TLSCertFile = ensurePath(spec.TLS.CertificateFile, mountPath, "tls.crt")
		params.TLSKeyFile = ensurePath(spec.TLS.PrivateKeyFile, mountPath, "tls.key")
		if spec.TLS.CAFile != "" {
			mountPathCA := mountPath
			if spec.TLS.CASecretName != "" {
				mountPathCA = mountPath + "ca"
			}
			params.TLSCAFile = ensurePath(spec.TLS.CAFile, mountPathCA, "")
		}
	}

	var buf bytes.Buffer
	if err := pgBouncerConfigTemplate.Execute(&buf, params); err != nil {
		return "", fmt.Errorf("could not render pgbouncer config: %v", err)
	}
	return buf.String(), nil
}

// connectionPoolerConfigChecksum returns the sha256 of the rendered config,
// used as a pod annotation so config changes roll the pooler pods.
func (c *Cluster) connectionPoolerConfigChecksum(role PostgresRole) (string, error) {
	ini, err := c.generatePgBouncerIni(role)
	if err != nil {
		return "", err
	}
	sum := sha256.Sum256([]byte(ini))
	return fmt.Sprintf("%x", sum), nil
}

// generateConnectionPoolerConfigMap builds the operator-owned ConfigMap holding
// the rendered pgbouncer.ini for the given role.
func (c *Cluster) generateConnectionPoolerConfigMap(role PostgresRole) (*v1.ConfigMap, error) {
	ini, err := c.generatePgBouncerIni(role)
	if err != nil {
		return nil, err
	}
	return &v1.ConfigMap{
		ObjectMeta: metav1.ObjectMeta{
			Name:            fmt.Sprintf("%s-config", c.connectionPoolerName(role)),
			Namespace:       c.Namespace,
			Labels:          c.connectionPoolerLabels(role, true).MatchLabels,
			Annotations:     c.annotationsSet(nil),
			OwnerReferences: c.ownerReferences(),
		},
		Data: map[string]string{
			pgBouncerConfigFileName: ini,
		},
	}, nil
}