package main

import (
	"database/sql"
	"log"
	"time"
)

// Config : holds information about a specific Config
type Config struct {
	ID        int       `json:"id"`
	Parameter string    `json:"parameter"`
	Val       string    `json:"val"`
	CreatedAt time.Time `json:"createdAt"`
	UpdatedAt time.Time `json:"updatedAt"`
}

// Configs : a list of Config items
type Configs []Config

const configTableCreationQuery = `CREATE TABLE IF NOT EXISTS configs (
	id int(10) unsigned AUTO_INCREMENT,
	parameter varchar(255),
	val varchar(255),
	createdAt datetime,
	updatedAt datetime,
	UNIQUE KEY parameter (parameter),
	PRIMARY KEY (id)
  )`

func ensureConfigTableExists(db *sql.DB) {
	if _, err := db.Exec(configTableCreationQuery); err != nil {
		log.Fatal(err)
	}
}

// getConfig : used during GET command
func (c *Config) getConfig(db *sql.DB) error {
	return db.QueryRow("SELECT parameter, val, createdAt, updatedAt FROM configs WHERE id=?", c.ID).Scan(&c.Parameter, &c.Val, &c.CreatedAt, &c.UpdatedAt)
}

// updateConfig : used during PUT command
func (c *Config) updateConfig(db *sql.DB) error {
	updStmt, updErr := db.Prepare("UPDATE configs SET parameter=?, val=?, updatedAt=? WHERE id=?")
	if updErr != nil {
		panic(updErr.Error()) // proper error handling instead of panic in your app
	}
	defer updStmt.Close() // Close the statement when we leave main() / the program terminates

	_, err := updStmt.Exec(c.Parameter, c.Val, time.Now(), c.ID)
	return err
}

// deleteConfig : used during DELETE command
func (c *Config) deleteConfig(db *sql.DB) error {
	_, err := db.Exec("DELETE FROM configs WHERE id=?", c.ID)
	return err
}

// createConfig : used during PUSH command
func (c *Config) createConfig(db *sql.DB) error {
	stmtIns, insErr := db.Prepare("INSERT INTO configs (parameter, val, createdAt, updatedAt) VALUES (?, ?, ?, ?);")
	if insErr != nil {
		panic(insErr.Error()) // proper error handling instead of panic in your app
	}
	defer stmtIns.Close() // Close the statement when we leave main() / the program terminates

	_, err := stmtIns.Exec(c.Parameter, c.Val, time.Now(), time.Now())
	return err
}

// getConfigs : used during GET command for all
func getConfigs(db *sql.DB, start, count int) (Configs, error) {
	rows, err := db.Query(
		"SELECT id, parameter, val, createdAt, updatedAt FROM configs LIMIT ? OFFSET ?",
		count, start)

	if err != nil {
		return nil, err
	}

	defer rows.Close()

	configs := Configs{}

	for rows.Next() {
		var c Config
		if err := rows.Scan(&c.ID, &c.Parameter, &c.Val, &c.CreatedAt, &c.UpdatedAt); err != nil {
			return nil, err
		}
		configs = append(configs, c)
	}

	return configs, nil
}