package main

import (
	"database/sql"
	_ "github.com/go-sql-driver/mysql"
	"log"
	"os"
	"time"
)

var db *sql.DB

func DSNGenerator() string {
	db_user := "atsebayt"
	db_password := "atsebayt"
	db_host := ""
	db_db := "atsebayt"

	if v, exists := os.LookupEnv("MYSQL_HOST"); exists {
		db_host = v
	}
	if v, exists := os.LookupEnv("MYSQL_PASSWORD"); exists {
		db_password = v
	} else if v, exists := os.LookupEnv("MYSQL_ROOT_PASSWORD"); exists {
		db_user = "root"
		db_password = v
	}
	if v, exists := os.LookupEnv("MYSQL_USER"); exists {
		db_user = v
	}
	if v, exists := os.LookupEnv("MYSQL_DATABASE"); exists {
		db_db = v
	}

	return db_user + ":" + db_password + "@" + db_host + "/" + db_db
}

func DBInit(dsn string) (err error) {
	if db, err = sql.Open("mysql", dsn+"?parseTime=true&foreign_key_checks=1"); err != nil {
		return
	}

	_, err = db.Exec(`SET SESSION sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';`)
	for i := 0; err != nil && i < 5; i += 1 {
		if _, err = db.Exec(`SET SESSION sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';`); err != nil && i <= 5 {
			log.Println("An error occurs when trying to connect to DB, will retry in 2 seconds: ", err)
			time.Sleep(2 * time.Second)
		}
	}

	return
}

func DBCreate() (err error) {
	if _, err = db.Exec(`
CREATE TABLE IF NOT EXISTS users(
  id_user INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
  login VARCHAR(255) NOT NULL UNIQUE,
  email VARCHAR(255) NOT NULL,
  firstname VARCHAR(255) NOT NULL,
  lastname VARCHAR(255) NOT NULL,
  time TIMESTAMP NOT NULL,
  promo MEDIUMINT NOT NULL,
  groups VARCHAR(255) NOT NULL,
  is_admin BOOLEAN NOT NULL DEFAULT FALSE
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return
	}
	if _, err := db.Exec(`
CREATE TABLE IF NOT EXISTS user_sessions(
  id_session BLOB(255) NOT NULL,
  id_user INTEGER,
  time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY(id_user) REFERENCES users(id_user)
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return err
	}
	if _, err := db.Exec(`
CREATE TABLE IF NOT EXISTS surveys(
  id_survey INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
  title VARCHAR(255),
  promo MEDIUMINT NOT NULL,
  shown BOOLEAN NOT NULL DEFAULT FALSE,
  corrected BOOLEAN NOT NULL DEFAULT FALSE,
  start_availability TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
  end_availability TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return err
	}
	if _, err := db.Exec(`
CREATE TABLE IF NOT EXISTS survey_quests(
  id_question INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
  id_survey INTEGER NOT NULL,
  title VARCHAR(255),
  description TEXT,
  placeholder VARCHAR(255),
  kind ENUM('text', 'int', 'ucq', 'mcq') NOT NULL,
  FOREIGN KEY(id_survey) REFERENCES surveys(id_survey)
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return err
	}
	if _, err := db.Exec(`
CREATE TABLE IF NOT EXISTS survey_proposals(
  id_proposal INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
  id_question INTEGER NOT NULL,
  label VARCHAR(255),
  FOREIGN KEY(id_question) REFERENCES survey_quests(id_question)
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return err
	}
	if _, err := db.Exec(`
CREATE TABLE IF NOT EXISTS survey_responses(
  id_response INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
  id_question INTEGER NOT NULL,
  id_user INTEGER NOT NULL,
  answer TEXT NOT NULL,
  time_submit TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
  score INTEGER,
  score_explanation TEXT,
  id_corrector INTEGER,
  time_scored TIMESTAMP NULL DEFAULT NULL,
  FOREIGN KEY(id_question) REFERENCES survey_quests(id_question),
  FOREIGN KEY(id_user) REFERENCES users(id_user),
  FOREIGN KEY(id_corrector) REFERENCES users(id_user)
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return err
	}
	if _, err := db.Exec(`
CREATE TABLE IF NOT EXISTS correction_templates(
  id_template INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
  id_question INTEGER NOT NULL,
  label VARCHAR(255) NOT NULL,
  score INTEGER,
  score_explanation TEXT,
  FOREIGN KEY(id_question) REFERENCES survey_quests(id_question)
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return err
	}
	if _, err := db.Exec(`
CREATE TABLE IF NOT EXISTS student_corrected(
  id_correction INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT,
  id_user INTEGER NOT NULL,
  id_template INTEGER NOT NULL,
  FOREIGN KEY(id_user) REFERENCES users(id_user),
  FOREIGN KEY(id_template) REFERENCES correction_templates(id_template)
) DEFAULT CHARACTER SET = utf8 COLLATE = utf8_bin;
`); err != nil {
		return err
	}
	if _, err := db.Exec(`
CREATE VIEW IF NOT EXISTS student_scores AS SELECT U.id_user, id_survey, Q.id_question, MAX(R.score) as score FROM survey_quests Q CROSS JOIN users U LEFT JOIN survey_responses R ON Q.id_question = R.id_question AND R.id_user = U.id_user GROUP BY Q.id_question, U.id_user;
`); err != nil {
		return err
	}
	return
}

func DBClose() error {
	return db.Close()
}

func DBPrepare(query string) (*sql.Stmt, error) {
	return db.Prepare(query)
}

func DBQuery(query string, args ...interface{}) (*sql.Rows, error) {
	return db.Query(query, args...)
}

func DBExec(query string, args ...interface{}) (sql.Result, error) {
	return db.Exec(query, args...)
}

func DBQueryRow(query string, args ...interface{}) *sql.Row {
	return db.QueryRow(query, args...)
}