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main.go
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main.go
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package main
import (
"database/sql"
"encoding/json"
"fmt"
"html/template"
"net/http"
"os"
"os/signal"
"syscall"
_ "github.com/mattn/go-sqlite3"
"github.com/op/go-logging"
)
//PaginateDataStruct fields for the AJAX response to paginate
type PaginateDataStruct struct {
Draw string `json:"draw"`
RecordsTotal int `json:"recordsTotal"`
RecordsFiltered int `json:"recordsFiltered"`
BookList []Book `json:"data"`
}
// Book Struct contains useful information
type Book struct {
Title string `json:"Title"`
Country string `json:"Country"`
Date string `json:"Date"`
Author string `json:"Author"`
ID string `json:"identifier"`
}
//Database path
var Database = `data/largeDB.db`
var db *sql.DB
//Here we store the recordsTotal and recordsFiltered value
var final int
//Format
var log = logging.MustGetLogger("example")
var format = logging.MustStringFormatter(
`%{color}%{time:15:04:05.000} %{shortfunc} ▶ %{level:.4s} %{id:03x}%{color:reset} %{message}`,
)
//search function returns the result of the query
func search(query string, args []interface{}) (dataList []Book) {
var book Book
rows, err := db.Query(query, args...)
if err != nil {
log.Critical("QueryRow: %v\n", err)
}
columns, err := rows.Columns()
if err != nil {
log.Critical(err.Error())
}
values := make([]sql.RawBytes, len(columns))
// rows.Scan wants '[]interface{}' as an argument, so we must copy the
// references into such a slice
// See http://code.google.com/p/go-wiki/wiki/InterfaceSlice for details
scanArgs := make([]interface{}, len(values))
for i := range values {
scanArgs[i] = &values[i]
}
for rows.Next() {
// get RawBytes from data
err = rows.Scan(scanArgs...)
if err != nil {
log.Critical(err.Error())
}
var value string
for i, col := range values {
// Here we can check if the value is nil (NULL value)
if col == nil {
value = "NULL"
} else {
value = string(col)
}
if columns[i] == "id" {
book.ID = value
}
if columns[i] == "Author" {
book.Author = value
}
if columns[i] == "Date" {
book.Date = value
}
if columns[i] == "Country" {
book.Country = value
}
if columns[i] == "Title" {
book.Title = value
}
}
dataList = append(dataList, book)
}
return dataList
}
//paging function is used to implement
func paging(w http.ResponseWriter, r *http.Request) {
log.Info(" - Method:", r.Method, " - /populateDataTable")
var paging PaginateDataStruct
var result []Book
var count, query string
var args []interface{}
if r.Method == "POST" {
r.ParseForm()
count = `SELECT count(*) as frequency FROM Book`
start := r.FormValue("start")
end := r.FormValue("length")
draw := r.FormValue("draw")
log.Info("Start: ", start+" Length: "+end+" Draw: "+draw)
searchValue := r.FormValue("search[value]")
if draw == "1" {
rows, err := db.Query(count)
if err != nil {
fmt.Printf("QueryRow: %v\n", err)
}
defer rows.Close()
for rows.Next() {
err = rows.Scan(&final)
if err != nil {
fmt.Println(err)
}
}
}
log.Infof("Records Filtered: %d", final)
if searchValue != "" {
log.Info("Search Value: " + searchValue)
query = `SELECT id,Title,Country,Date,Author FROM Book
WHERE Title LIKE ? OR Country Like ?
OR Date Like ? OR Author Like ?
ORDER BY Title
Limit ? , ?;`
p := searchValue + "%"
args = []interface{}{p, p, p, p, start, end}
aux := []interface{}{p, p, p, p}
result = search(query, args)
//Here we obtain the number of results
rows, err := db.Query(`SELECT COUNT(*) FROM Book
WHERE Title LIKE ? OR Country Like ?
OR Date Like ? OR Author Like ?
ORDER BY Title`, aux...)
if err != nil {
fmt.Printf("QueryRow: %v\n", err)
}
defer rows.Close()
for rows.Next() {
err = rows.Scan(&final)
if err != nil {
fmt.Println(err)
}
}
} else {
query = `SELECT id,Title,Country,Date,Author FROM Book
ORDER BY Title
Limit ? , ?;`
args = []interface{}{start, end}
result = search(query, args)
}
paging.BookList = result
paging.Draw = draw
paging.RecordsFiltered = final
paging.RecordsFiltered = final
e, err := json.Marshal(paging)
if err != nil {
fmt.Println(err)
return
}
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusOK)
w.Write(e)
} else {
http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
}
}
func mainpage(w http.ResponseWriter, r *http.Request) {
log.Info(" - Method:", r.Method, " - /")
if r.Method == "GET" {
t, _ := template.ParseFiles("html/index.html")
t.Execute(w, nil)
} else {
http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
}
}
func init() {
log.Info(" - Setup our Ctrl+C handler...")
SetupCloseHandler()
log.Info(" - Opening the database...")
var err error
db, err = sql.Open("sqlite3", Database)
if err != nil {
fmt.Println(err)
}
db.SetMaxOpenConns(1)
db.Exec("PRAGMA journal_mode=MEMORY;")
db.Exec("PRAGMA _synchronous=OFF;")
statement, err := db.Prepare("CREATE TABLE IF NOT EXISTS Book (id INTEGER PRIMARY KEY, Title TEXT, Country TEXT, Date TEXT, Author TEXT)")
if err != nil {
fmt.Println(err)
}
statement.Exec()
statement, err = db.Prepare("CREATE INDEX IF NOT EXISTS tag_title ON Book (Title);")
if err != nil {
fmt.Println(err)
}
statement.Exec()
statement, err = db.Prepare("CREATE INDEX IF NOT EXISTS tag_country ON Book (Country);")
if err != nil {
fmt.Println(err)
}
statement.Exec()
statement, err = db.Prepare("CREATE INDEX IF NOT EXISTS tag_date ON Book (Date);")
if err != nil {
fmt.Println(err)
}
statement.Exec()
statement, err = db.Prepare("CREATE INDEX IF NOT EXISTS tag_author ON Book (Author);")
if err != nil {
fmt.Println(err)
}
statement.Exec()
}
// SetupCloseHandler https://golangcode.com/handle-ctrl-c-exit-in-terminal/
func SetupCloseHandler() {
c := make(chan os.Signal, 2)
signal.Notify(c, os.Interrupt, syscall.SIGTERM)
go func() {
<-c
log.Info("\r- Ctrl+C pressed in Terminal, closing the DB")
if err := db.Close(); err != nil {
log.Critical(err)
}
os.Exit(0)
}()
}
func main() {
http.HandleFunc("/", mainpage)
http.HandleFunc("/populateDataTable", paging)
fileServer := http.FileServer(http.Dir("html/static"))
http.Handle("/static/", http.StripPrefix("/static/", fileServer))
log.Info(" - Listening on port 8080...")
err := http.ListenAndServe(":8080", nil)
if err != nil {
log.Fatal(" - ListenAndServe: ", err)
}
}