package database

import (
	// External
	"git.gibonuddevalla.se/go/dbschema"
	"github.com/jmoiron/sqlx"
	_ "github.com/lib/pq"

	// Internal
	"git.gibonuddevalla.se/go/webservice/config"
	"git.gibonuddevalla.se/go/webservice/session"

	// Standard
	"database/sql"
	"encoding/json"
	"fmt"
	"log/slog"
)

type SqlProvider func(string, int) ([]byte, bool)

type T struct {
	cfg    config.DatabaseDetails
	Conn   *sqlx.DB
	logger *slog.Logger

	sqlProvider SqlProvider
	logProvider func(string, string)
}

func New(cfg config.DatabaseDetails) (db *T) { // {{{
	db = new(T)
	db.cfg = cfg
	db.logProvider = db.defaultLogProvider
	return
} // }}}

func (db *T) SetLogger(l *slog.Logger) { // {{{
	db.logger = l
} // }}}
func (db *T) SetSQLProvider(fn func(string, int) ([]byte, bool)) { // {{{
	db.sqlProvider = fn
} // }}}
func (db *T) SetLogProvider(fn func(string, string)) { // {{{
	db.logProvider = fn
} // }}}

func (db *T) defaultLogProvider(category, msg string) { // {{{
	db.logger.Info("database", category, msg)
} // }}}
func webserviceSQLProvider(dbname string, version int) ([]byte, bool) { // {{{
	sql := map[int]string{
		1: `
			CREATE TABLE _webservice.user (
				id serial NOT NULL,
				"name"     varchar NOT NULL,
				"username" varchar NOT NULL,
				"password" char(96) NOT NULL,
				last_login timestamp with time zone NOT NULL DEFAULT '1970-01-01 00:00:00',
				CONSTRAINT user_pk PRIMARY KEY (id),
				CONSTRAINT user_un UNIQUE (username)
			);

			CREATE TABLE "_webservice"."session" (
				id         serial NOT NULL,
				user_id    int4 NULL,
				"uuid"     char(36) NOT NULL,
				created    timestamp with time zone NOT NULL DEFAULT NOW(),
				last_used  timestamp with time zone NOT NULL DEFAULT NOW(),
				CONSTRAINT session_pk PRIMARY KEY (id),
				CONSTRAINT session_un UNIQUE ("uuid"),
				CONSTRAINT session_user_fk FOREIGN KEY (user_id) REFERENCES "_webservice"."user"(id) ON DELETE CASCADE ON UPDATE CASCADE
			);

			CREATE EXTENSION IF NOT EXISTS pgcrypto SCHEMA _webservice;

			CREATE FUNCTION _webservice.password_hash(salt_hex char(32), pass bytea)
			RETURNS char(96)
			LANGUAGE plpgsql
			AS
			$$
			BEGIN
				RETURN (
					SELECT
						salt_hex ||
						encode(
							sha256(
								decode(salt_hex, 'hex') || /* salt in binary */
								pass                       /* password */
							),
							'hex'
						)
				);
			END;
			$$;
		`,

		2: `
			ALTER TABLE "_webservice"."session" ADD mfa jsonb DEFAULT '{}' NOT NULL;
		`,
	}

	statement, found := sql[version]
	return []byte(statement), found
} // }}}

func (db *T) Upgrade() (err error) { // {{{
	upgrader := dbschema.NewUpgrader("_webservice")
	upgrader.SetSqlCallback(webserviceSQLProvider)
	upgrader.SetLogCallback(db.logProvider)
	if err = upgrader.AddDatabase(
		db.cfg.Host,
		db.cfg.Port,
		db.cfg.Name,
		db.cfg.Username,
		db.cfg.Password,
	); err != nil {
		return
	}

	err = upgrader.Run()
	if err != nil {
		return
	}

	upgrader = dbschema.NewUpgrader("_db")
	upgrader.SetSqlCallback(db.sqlProvider)
	upgrader.SetLogCallback(db.logProvider)
	if err = upgrader.AddDatabase(
		db.cfg.Host,
		db.cfg.Port,
		db.cfg.Name,
		db.cfg.Username,
		db.cfg.Password,
	); err != nil {
		return
	}

	err = upgrader.Run()
	return
} // }}}
func (db *T) Connect() (err error) { // {{{
	db.logger.Info("database", "host", db.cfg.Host, "port", db.cfg.Port, "name", db.cfg.Name)

	dbConn := fmt.Sprintf(
		"host=%s port=%d user=%s password=%s dbname=%s sslmode=disable",
		db.cfg.Host,
		db.cfg.Port,
		db.cfg.Username,
		db.cfg.Password,
		db.cfg.Name,
	)

	if db.Conn, err = sqlx.Connect("postgres", dbConn); err != nil {
		return
	}

	return
} // }}}

func (db *T) Authenticate(username, password string) (authenticated bool, userID int, err error) { // {{{
	var rows *sql.Rows
	if rows, err = db.Conn.Query(`
		SELECT id
		FROM _webservice.user
		WHERE
			LOWER(username) = LOWER($1) AND
			password = _webservice.password_hash(SUBSTRING(password FROM 1 FOR 32), $2::bytea)
		`,
		username,
		password,
	); err != nil {
		return
	}
	defer rows.Close()

	if rows.Next() {
		rows.Scan(&userID)
		authenticated = userID > 0
	}
	return
} // }}}
func (db *T) NewSession(uuid string) (err error) { // {{{
	_, err = db.Conn.Exec("INSERT INTO _webservice.session(uuid) VALUES($1)", uuid)
	return
} // }}}
func (db *T) RetrieveSession(uuid string) (sess *session.T, err error) { // {{{
	var rows *sqlx.Rows
	rows, err = db.Conn.Queryx(`
		WITH session_data AS (
			UPDATE _webservice.session
			SET
				last_used=NOW()
			WHERE
				uuid=$1
			RETURNING
				uuid, created, last_used, user_id, mfa
		)
		SELECT
			sd.uuid, sd.created, sd.last_used,
			COALESCE(u.username, '') AS username,
			COALESCE(u.name, '') AS name,
			COALESCE(u.id, 0) AS user_id,
			mfa
		FROM session_data sd
		LEFT JOIN _webservice.user u ON sd.user_id = u.id
		`,
		uuid,
	)
	if err != nil {
		return
	}
	defer rows.Close()

	for rows.Next() {
		sess = new(session.T)
		err = rows.StructScan(sess)
		sess.Authenticated = sess.UserID > 0
	}
	return
} // }}}
func (db *T) SetSessionUser(uuid string, userID int) (err error) { // {{{
	_, err = db.Conn.Exec(`
		UPDATE _webservice.session
		SET
			user_id = CASE
				WHEN $1 <= 0 THEN NULL
				ELSE $1
			END
		WHERE uuid=$2
		`,
		userID,
		uuid,
	)
	if err != nil {
		return
	}
	return
} // }}}
func (db *T) SetSessionMFA(uuid string, mfa any) (err error) { // {{{
	mfaByte, _ := json.Marshal(mfa)
	_, err = db.Conn.Exec(`
		UPDATE _webservice.session
		SET
			mfa = $2
		WHERE
			uuid = $1
		`,
		uuid,
		mfaByte,
	)
	if err != nil {
		return
	}
	return
} // }}}
func (db *T) UpdateUserTime(userID int) (err error) { // {{{
	_, err = db.Conn.Exec(`UPDATE _webservice.user SET last_login=NOW() WHERE id=$1`, userID)
	return
} // }}}

func (db *T) CreateUser(username, password, name string) (userID int64, err error) { // {{{
	var row *sql.Row
	row = db.Conn.QueryRow(`
		INSERT INTO _webservice.user(username, password, name)
		VALUES(
			$1,
			_webservice.password_hash(
				/* salt in hex */
				ENCODE(_webservice.gen_random_bytes(16), 'hex'),

				/* password */
				$2::bytea
			),
			$3
		)
		ON CONFLICT (username) DO UPDATE
		SET username = EXCLUDED.username
		RETURNING id
		`,
		username,
		password,
		name,
	)

	err = row.Scan(&userID)
	return
} // }}}
func (db *T) ChangePassword(userID int, currentPassword, newPassword string) (changed bool, err error) { // {{{
	var res sql.Result
	res, err = db.Conn.Exec(`
		UPDATE _webservice.user
		SET
			"password" = _webservice.password_hash(
				/* salt in hex */
				ENCODE(_webservice.gen_random_bytes(16), 'hex'),

				/* password */
				$3::bytea
			)
		WHERE
			id = $1 AND
			"password" = _webservice.password_hash(SUBSTRING(password FROM 1 FOR 32), $2::bytea)

		`,
		userID,
		currentPassword,
		newPassword,
	)

	var rowsAffected int64
	rowsAffected, err = res.RowsAffected()
	if err != nil {
		return
	}

	changed = (rowsAffected == 1)
	return
} // }}}

// vim: foldmethod=marker