/*
 * Sicherheitsunterweisung
 * Copyright (C) 2023  Jason Streifling
 *
 * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package data

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

	"github.com/go-sql-driver/mysql"
)

func OpenDB(dbName string) (*DB, error) {
	var err error
	db := new(DB)

	cfg := mysql.NewConfig()
	cfg.DBName = dbName
	cfg.User, cfg.Passwd, err = getCredentials()
	if err != nil {
		return nil, fmt.Errorf("error: OpenDB: getCredentials(): %v", err)
	}

	db.DB, err = sql.Open("mysql", cfg.FormatDSN())
	if err != nil {
		return nil, fmt.Errorf("error: OpenDB: sql.Open(\"mysql\", cfg.FormatDSN()): %v", err)
	}
	if err := db.Ping(); err != nil {
		return nil, fmt.Errorf("error: OpenDB: db.Ping(): %v", err)
	}

	return db, nil
}

func (db *DB) WriteBriefing(b *Briefing) error {
	query := `
  INSERT INTO briefings
  	(datetime, location, document, as_of, instructor_id)
  VALUES
  	(?, ?, ?, ?, ?)
  `

	result, err := db.Exec(query, b.DateTime, b.Location, b.Document, b.AsOf, b.InstructorID)
	if err != nil {
		return fmt.Errorf("error: *DB.writeBriefing: db.Exec(): %v", err)
	}

	b.ID, err = result.LastInsertId()
	if err != nil {
		return fmt.Errorf("error: *DB.writeBriefing: result.LastInsertId(): %v", err)
	}

	return nil
}

func (db *DB) WriteParticipant(p *Participant) error {
	query := `
  INSERT INTO participants
  	(first_name, last_name, company)
  VALUES
  	(?, ?, ?)
  `

	result, err := db.Exec(query, p.FirstName, p.LastName, p.Company)
	if err != nil {
		return fmt.Errorf("error: *DB.writeParticipants: db.Exec(): %v", err)
	}

	p.ID, err = result.LastInsertId()
	if err != nil {
		return fmt.Errorf("error: *DB.writeParticipants: result.LastInsertId(): %v", err)
	}

	return nil
}

func (db *DB) WriteGivenAnswers(b Briefing, p Participant, sq []Question, givenAnswers []int) error {
	query := `
    INSERT INTO given_answers
    	(briefing_id, participant_id, question_id, given_answer)
    VALUES
    	(?, ?, ?, ?)
    `

	for i, q := range sq {
		_, err := db.Exec(query, b.ID, p.ID, q.ID, givenAnswers[i])
		if err != nil {
			return fmt.Errorf("error: *DB.WriteGivenAnswers: db.Exec(): %v", err)
		}
	}

	return nil
}

func (db *DB) GetAllOverviewTableData() ([]OverviewTableData, error) {
	query := `
  SELECT
    i.first_name,
    i.last_name,
    b.datetime,
    b.location,
    b.document,
    b.as_of,
    p.first_name,
    p.last_name,
    p.company
  FROM given_answers AS g
    INNER JOIN briefings AS b
      ON b.id = g.briefing_id
    INNER JOIN participants AS p
      ON p.id = g.participant_id
    INNER JOIN questions AS q
      ON q.id = g.question_id
    INNER JOIN instructors AS i
      ON i.id = b.instructor_id
  WHERE
    q.id = 1
  ORDER BY
    b.id DESC,
    p.id
  `

	rows, err := db.Query(query)
	if err != nil {
		return nil, fmt.Errorf("error: *DB.ReadAllBriefings: db.Query(): %v", err)
	}
	defer rows.Close()

	data := make([]OverviewTableData, 0)
	for rows.Next() {
		otd := OverviewTableData{}

		err := rows.Scan(
			&otd.InstructorFirstName,
			&otd.InstructorLastName,
			&otd.BriefingDateTime,
			&otd.BriefingLocation,
			&otd.BriefingDocument,
			&otd.BriefingAsOf,
			&otd.ParticipantFirstName,
			&otd.ParticipantLastName,
			&otd.ParticipantCompany,
		)
		if err != nil {
			return nil, fmt.Errorf("error: *DB.ReadAllBriefings: rows.Scan(): %v", err)
		}

		data = append(data, otd)
	}

	return data, nil
}

func (db *DB) GetOverviewTableDataByName(n string) ([]OverviewTableData, error) {
	query := `
  SELECT
    i.first_name,
    i.last_name,
    b.datetime,
    b.location,
    b.document,
    b.as_of,
    p.first_name,
    p.last_name,
    p.company
  FROM given_answers AS g
    INNER JOIN briefings AS b
      ON b.id = g.briefing_id
    INNER JOIN participants AS p
      ON p.id = g.participant_id
    INNER JOIN questions AS q
      ON q.id = g.question_id
    INNER JOIN instructors AS i
      ON i.id = b.instructor_id
  WHERE
    q.id = 1 AND
    (
      i.first_name LIKE ? OR
      i.last_name LIKE ? OR
      p.first_name LIKE ? OR
      p.last_name LIKE ?
    )
  ORDER BY
    b.id DESC,
    p.id
  `

	rows, err := db.Query(query, "%"+n+"%", "%"+n+"%", "%"+n+"%", "%"+n+"%")
	if err != nil {
		return nil, fmt.Errorf("error: *DB.GetOverviewTableDataByName: db.Query(): %v", err)
	}
	defer rows.Close()

	data := make([]OverviewTableData, 0)
	for rows.Next() {
		otd := OverviewTableData{}

		err := rows.Scan(
			&otd.InstructorFirstName,
			&otd.InstructorLastName,
			&otd.BriefingDateTime,
			&otd.BriefingLocation,
			&otd.BriefingDocument,
			&otd.BriefingAsOf,
			&otd.ParticipantFirstName,
			&otd.ParticipantLastName,
			&otd.ParticipantCompany,
		)
		if err != nil {
			return nil, fmt.Errorf("error: *DB.ReadAllBriefings: rows.Scan(): %v", err)
		}

		data = append(data, otd)
	}

	return data, nil
}

func (db *DB) GetLastID(table string) (int, error) {
	var id int
	query := `
  SELECT id
  FROM ?
  ORDER BY id DESC
    LIMIT 0, 1
  `

	row := db.QueryRow(query, table)
	if err := row.Scan(&id); err != nil {
		return -1, fmt.Errorf("error: *DB.GetLastID: row.Scan(): %v", err)
	}

	return id, nil
}

func (db *DB) GetInstructors() ([]*Instructor, error) {
	query := `
  SELECT *
  FROM instructors
  ORDER BY
    last_name,
    first_name
  `

	rows, err := db.Query(query)
	if err != nil {
		return nil, fmt.Errorf("error: *DB.GetInstructors: db.Query(): %v", err)
	}
	defer rows.Close()

	instructors := make([]*Instructor, 0)
	for rows.Next() {
		instructor := new(Instructor)

		if err = rows.Scan(&instructor.ID, &instructor.FirstName, &instructor.LastName); err != nil {
			return nil, fmt.Errorf("error: *DB.GetInstructors: rows.Scan(): %v", err)
		}

		instructors = append(instructors, instructor)
	}

	return instructors, nil
}

func (db *DB) GetQuestions(nums []string) ([]Question, error) {
	query := `
  SELECT *
  FROM questions
  WHERE id IN (` + strings.Join(nums, ", ") + `)
  `

	rows, err := db.Query(query)
	if err != nil {
		return nil, fmt.Errorf("error: *DB.GetQuestions: db.Query(): %v", err)
	}
	defer rows.Close()

	// TODO: not scalable
	questions := make([]Question, 0)
	for rows.Next() {
		q := Question{Answers: make([]Answer, 4)}
		q.Answers[0].ID = 1
		q.Answers[1].ID = 2
		q.Answers[2].ID = 3
		q.Answers[3].ID = 4

		if err := rows.Scan(&q.ID, &q.Text, &q.Answers[0].Text, &q.Answers[1].Text, &q.Answers[2].Text, &q.Answers[3].Text, &q.Correct); err != nil {
			return nil, fmt.Errorf("error: *DB.GetQuestions: rows.Scan(): %v", err)
		}

		questions = append(questions, q)
	}

	return questions, nil
}

func (db *DB) GetGivenAnswers(bid, pid int64, sq []Question) ([]int, error) {
	answers := make([]int, len(sq))
	query := `
  SELECT given_answer
  FROM given_answers
  WHERE
    briefing_id = ? AND
    participant_id = ? AND
    question_id = ?
  `

	for i, q := range sq {
		row := db.QueryRow(query, bid, pid, q.ID)
		if err := row.Scan(&answers[i]); err != nil {
			return nil, fmt.Errorf("error: *DB.GetGivenAnswers: row.Scan(): %v", err)
		}
	}

	return answers, nil
}