// ============================================================================= // Auth: Alex Celani // File: server.go // Revn: 10-05-2023 2.0 // Func: host connection, reply to speak.go // // TODO: add more /codes/ to handle // add flags // write usage and errors to logfile // send logfile to client on request // ============================================================================= // CHANGE LOG // ----------------------------------------------------------------------------- // 05-13-2022: init // 08-29-2023: gutted and rewrote // commented // 09-12-2023: imported io/ioutil, strings, strconv // added size conversation // added file read function, fread() // commented // 09-21-2023: began rewrite of handle() // 09-26-2023: got /list/ command working // got /add/ command (mostly) working //*10-02-2023: commented handle() // added checks to /qr/ and /r2/ to make sure recv'd // length is valid // wrote writeFile() //*10-05-2023: commented // imported check() to ignore EOF // fixed bug in /r2/ where removing quote at final // position would break // removed deadcode from /r2/, unused "quit" bool? // // ============================================================================= package main import ( "fmt" // Println "io" // io.EOF "io/ioutil" // ReadFile "net" // ResovleTCPAddr, ListenTCP, listener.Accept // conn.Read,Write "os" // Exit "strconv" // Itoa "strings" // Split ) // handle errors catastrophically func check( err error ) { if err != nil { // error is not nil on error // print error fmt.Println( "Fatal: ", err.Error() ) os.Exit( 1 ) // bail } } // FIXME clean this two check() shit up // print errors if they occur, quit func checkN( err error, conn net.Conn ) { var errep string // declare error report string switch err { // switch case over error input case nil: // if there was no error // then there was no error errep = "err is nil" case io.EOF: // if there was an End Of File error errep = "Error: " + err.Error() // document error conn.Close() // close connection default: // anything besides those are a big deal errep = "Fatal: " + err.Error() } var critical bool // declare critical error flag // must be neither nil nor EOF critical = err != nil && err != io.EOF if critical { // XXX critical print // TODO at some point, critical should be logging instead of // printing, only verbose should print fmt.Println( "check() -> ", errep ) } if critical { // if there was a critical error os.Exit( 1 ) // cut and run } } // read file and create quote list func fread() string { // open file "quotes", read entire file as bytes into qfile qfile, err := ioutil.ReadFile( "quotes" ) check( err ) // make sure read works // cast bytes to string, split string over newline into array qlist = strings.Split( string( qfile ), "\n" ) // remove last item in list ( trailing newline leaves empty item ) qlist = qlist[:len( qlist ) - 1] if false { // XXX debug print ( next ) for _, q := range qlist { // iterate over all quotes in list fmt.Println( q ) // print quote } } return string( qfile ) // return file as string } // write qfile back to file func writeFile( f string ) { // open file list.q as variable file file, err := os.Create( "list.q" ) check( err ) // make sure open worked // write input string ( quote file ) back to file _, err = file.WriteString( f ) check( err ) // make sure writeback worked } // handle connections ( new and improved ) func handle( conn net.Conn ) { // create buffer to hold read message var buffer [256]byte // read n bytes from client n, err := conn.Read( buffer[:] ) checkN( err, conn ) // make sure read worked // cast message to string, take first n bytes, split over @ command := strings.Split( string( buffer[:n] ), "@" ) // declare response string var resp string switch command[0] { // switch/case over opcode case "sr": // /sr/, size request // get length of list, convert to string // XXX probably no reason to have this declaration scheme var num string = strconv.Itoa( len( qlist ) ) // concat and send resp = "sa@" + num // size answer case "qr": // /qr/, quote request // convert message argument to string to make sure it's a // valid number num, nerr := strconv.Atoi( command[1] ) // nerr will not be nil if comm[1] is not a number if nerr != nil { // formulate an error message // TODO flesh this out more resp = "ba@qr@!" // bad answer } else { // comm[1] was a number, but... switch { // how do we know it's a valid number case num > len( qlist ): // bad answer in quote request resp = "ba@qr@>" // why bad? num is > case num < 0: // bad answer in quote request resp = "ba@qr@-" // why bad? num is - default: // good num, get quote, send off resp = "qa@" + qlist[num] // quote answer } } case "lr": // /lr/, list request // just concat entire list to send //resp = "la@" + qfile[:len( qfile ) - 1] // list answer resp = "la@" + qfile // list answer // TODO what happens if this is longer than 256 char? case "ar": // /ar/, add request // append new quote to list qlist = append( qlist, command[1] ) // also append new quote to file variable qfile = qfile + "\n" + command[1] writeFile( qfile ) resp = "aa@success" // add answer // TODO write to file case "r1": // /r1/, remove request 1 // same as list, just send whole file resp = "r1@" + qfile // remove request 1 case "r2": // /r2/, remove request 2 // convert message argument to string to make sure it's a // valid number num, nerr := strconv.Atoi( command[1] ) // nerr will not be nil if comm[1] is not a number if nerr != nil { // formulate an error message // TODO flesh this out more resp = "ba@r2@!" // bad answer } else { // comm[1] was a number, but... num = num - 1 switch { // how do we know it's a valid number // valid numbers are from 0 - len-1 case num > len( qlist ): // bad answer in quote request resp = "ba@r2@>" // why bad? num is > case num < 0: // bad answer in quote request resp = "ba@r2@-" // why bad? num is - // if num is not OUT OF RANGE, must be in range default: // replace the quote at that position with // final quote qlist[num] = qlist[len( qlist ) - 1] // remove second copy of quote qlist = qlist[:len( qlist ) - 1] // O(1) remove from list at any position // must entirely recreate quote string var f string = "" // init empty string // iterate over list, disregard index for _, v := range qlist { // add next quote to file and separate // quotes with newline f = f + v + "\n" } // remove trailing newline, to prevent ghost f = f[:len( f ) - 1] // quote in lr // reassign global string variable to // recreated quote string qfile = f writeFile( qfile ) // write back to file // let client know remove was successful resp = "r2@success" } } case "te": // /te/, transaction end // TODO should I be sending something? // TODO is it better to close now or outside of handle() conn.Close() // close connection and leave return // return from handle(), finish connection default: // opcode not recognized // TODO there should be more being down, here, right? return // return from handle(), finish connection } // write response to client _, err = conn.Write( []byte( resp ) ) checkN( err, conn ) // make sure write worked handle( conn ) // call handle() again to get response from client } // globals var qlist []string // list of quotes var qfile string // file object // main, create port and wait for connection func main() { qfile = fread() // read quote file, init ( global ) list of quotes service := ":1300" // create service on ip and port // resolve ip address and port addr, err := net.ResolveTCPAddr( "tcp", service ) check( err ) // make sure ip resolves // create listener object from ip:port listener, err := net.ListenTCP( "tcp", addr ) for { // wait, create connection when found conn, err := listener.Accept() check( err ) // make sure connection works go handle( conn ) // handle connection } os.Exit( 0 ) // exeunt }