package main

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

// TagValue : holds information about a specific TagValue
type TagValue struct {
	ID        int       `json:"id"`
	TagID     int       `json:"tagId"`
	Val       string    `json:"val"`
	TagName   int       `json:"tagName"`
	Units     int       `json:"units"`
	DataType  string    `json:"dataType"`
	CreatedAt time.Time `json:"createdAt"`
	UpdatedAt time.Time `json:"updatedAt"`
}

// TagValues : a list of TagValue items
type TagValues []TagValue

const tagValueTableCreationQuery = `CREATE TABLE IF NOT EXISTS tagValues (
	id int(10) unsigned NOT NULL AUTO_INCREMENT,
	tagId int(10) unsigned,
	val varchar(64),
	createdAt datetime,
	updatedAt datetime,
	PRIMARY KEY (id),
	CONSTRAINT fk_tag FOREIGN KEY (tagId) REFERENCES tags(id)
  )`

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

// getTagValue : used during GET command
func (t *TagValue) getTagValue(db *sql.DB) error {
	sqlQuery := `SELECT 
			tagValues.tagId, 
			tagValues.val, 
			tags.name,
			tags.units,
			dataTypes.dataType,
			tagValues.createdAt, 
			tagValues.updatedAt 
		FROM tagValues 
		JOIN tags ON tagValues.tagId = tags.id
		JOIN dataTypes ON tags.dataTypeId = dataTypes.id
		WHERE tagValues.id=?`
	return db.QueryRow(sqlQuery, t.ID).Scan(&t.TagID, &t.Val, &t.TagName, &t.Units, &t.DataType, &t.CreatedAt, &t.UpdatedAt)
}

// updateTagValue : used during PUT command
func (t *TagValue) updateTagValue(db *sql.DB) error {
	updStmt, updErr := db.Prepare("UPDATE tagValues SET tagId=?, 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(t.TagID, t.Val, time.Now(), t.ID)
	return err
}

// deleteTagValue : used during DELETE command
func (t *TagValue) deleteTagValue(db *sql.DB) error {
	_, err := db.Exec("DELETE FROM tagValues WHERE id=?", t.ID)
	return err
}

// createTagValue : used during PUSH command
func (t *TagValue) createTagValue(db *sql.DB) error {
	stmtIns, insErr := db.Prepare("INSERT INTO tagValues (tagId, 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(t.TagID, t.Val, time.Now(), time.Now())
	return err
}

// getTagValues : used during GET command for all
func getTagValues(db *sql.DB, start, count int) (TagValues, error) {
	sqlQuery := `SELECT 
			tagValues.id,
			tagValues.tagId, 
			tagValues.val, 
			tags.name,
			tags.units,
			dataTypes.dataType,
			tagValues.createdAt, 
			tagValues.updatedAt 
		FROM tagValues 
		JOIN tags ON tagValues.tagId = tags.id
		JOIN dataTypes ON tags.dataTypeId = dataTypes.id
		LIMIT ? OFFSET ?`
	rows, err := db.Query(sqlQuery, count, start)

	if err != nil {
		return nil, err
	}

	defer rows.Close()

	tagValues := TagValues{}

	for rows.Next() {
		var t TagValue
		if err := rows.Scan(&t.ID, &t.TagID, &t.Val, &t.TagName, &t.Units, &t.DataType, &t.CreatedAt, &t.UpdatedAt); err != nil {
			return nil, err
		}
		tagValues = append(tagValues, t)
	}

	return tagValues, nil
}