package postgresql

import (
	"database/sql"
	"fmt"
	"strings"
	"sync"

	"github.com/hashicorp/vault/logical"
	"github.com/hashicorp/vault/logical/framework"
	"github.com/lib/pq"
)

func Factory(conf *logical.BackendConfig) (logical.Backend, error) {
	return Backend().Setup(conf)
}

func Backend() *framework.Backend {
	var b backend
	b.Backend = &framework.Backend{
		Help: strings.TrimSpace(backendHelp),

		PathsSpecial: &logical.Paths{
			Root: []string{
				"config/*",
			},
		},

		Paths: []*framework.Path{
			pathConfigConnection(&b),
			pathConfigLease(&b),
			pathRoles(&b),
			pathRoleCreate(&b),
		},

		Secrets: []*framework.Secret{
			secretCreds(&b),
		},

		Clean: b.ResetDB,
	}

	return b.Backend
}

type backend struct {
	*framework.Backend

	db   *sql.DB
	lock sync.Mutex
}

// DB returns the database connection.
func (b *backend) DB(s logical.Storage) (*sql.DB, error) {
	b.lock.Lock()
	defer b.lock.Unlock()

	// If we already have a DB, we got it!
	if b.db != nil {
		return b.db, nil
	}

	// Otherwise, attempt to make connection
	entry, err := s.Get("config/connection")
	if err != nil {
		return nil, err
	}
	if entry == nil {
		return nil,
			fmt.Errorf("configure the DB connection with config/connection first")
	}

	var connConfig connectionConfig
	if err := entry.DecodeJSON(&connConfig); err != nil {
		return nil, err
	}

	conn := connConfig.ConnectionString
	if len(conn) == 0 {
		conn = connConfig.ConnectionURL
	}

	// Ensure timezone is set to UTC for all the conenctions
	if strings.HasPrefix(conn, "postgres://") || strings.HasPrefix(conn, "postgresql://") {
		var err error
		conn, err = pq.ParseURL(conn)
		if err != nil {
			return nil, err
		}
	}
	conn += " timezone=utc"

	b.db, err = sql.Open("postgres", conn)
	if err != nil {
		return nil, err
	}

	// Set some connection pool settings. We don't need much of this,
	// since the request rate shouldn't be high.
	b.db.SetMaxOpenConns(connConfig.MaxOpenConnections)

	return b.db, nil
}

// ResetDB forces a connection next time DB() is called.
func (b *backend) ResetDB() {
	b.lock.Lock()
	defer b.lock.Unlock()

	if b.db != nil {
		b.db.Close()
	}

	b.db = nil
}

// Lease returns the lease information
func (b *backend) Lease(s logical.Storage) (*configLease, error) {
	entry, err := s.Get("config/lease")
	if err != nil {
		return nil, err
	}
	if entry == nil {
		return nil, nil
	}

	var result configLease
	if err := entry.DecodeJSON(&result); err != nil {
		return nil, err
	}

	return &result, nil
}

const backendHelp = `
The PostgreSQL backend dynamically generates database users.

After mounting this backend, configure it using the endpoints within
the "config/" path.
`