import (
"gorilla/mux"
"net/http"
"fmt"
"strconv"
)

const GETALL string = "GETALL"
const GETONE string = "GETONE"
const POST string   = "POST"
const PUT string    = "PUT"
const DELETE string = "DELETE"

type clichePair struct {
Id      int
Cliche  string
Counter string
}

// Message sent to goroutine that accesses the requested resource.
type crudRequest struct {
verb     string
cp       * clichePair
id       int
cliche   string
counter  string
confirm  chan string
}

var clichesList = [] * clichePair {}
var masterId = 1
var crudRequests chan * crudRequest

// GET /
// GET /cliches
func ClichesAll ( res http . ResponseWriter , req * http. Request ) {
cr := &crudRequest { verb : GETALL , confirm : make ( chan string )}
completeRequest ( cr , res , "read all" )
}

// GET /cliches/id
func ClichesOne ( res http . ResponseWriter , req * http. Request ) {
id := getIdFromRequest ( req )
cr := &crudRequest { verb : GETONE , id : id , confirm : make ( chan string )}
completeRequest ( cr , res , "read one" )
}

// POST /cliches
func ClichesCreate ( res http . ResponseWriter , req * http. Request ) {
cliche , counter := getDataFromRequest ( req )
cp := new ( clichePair )
cp . Cliche = cliche
cp . Counter = counter
cr := &crudRequest { verb : POST , cp : cp , confirm : make ( chan string )}
completeRequest ( cr , res , "create" )
}

// PUT /cliches/id
func ClichesEdit ( res http . ResponseWriter , req * http. Request ) {
id := getIdFromRequest ( req )
cliche , counter := getDataFromRequest ( req )
cr := &crudRequest { verb : PUT , id : id , cliche : cliche , counter : counter , confirm : make ( chan string )}
completeRequest ( cr , res , "edit" )
}

// DELETE /cliches/id
func ClichesDelete ( res http . ResponseWriter , req * http. Request ) {
id := getIdFromRequest ( req )
cr := &crudRequest { verb : DELETE , id : id , confirm : make ( chan string )}
completeRequest ( cr , res , "delete" )
}

func completeRequest ( cr * crudRequest , res http . ResponseWriter , logMsg string ) {
crudRequests< - cr
msg := < - cr . confirm
res . Write ([] byte ( msg ))
logIt ( logMsg )
}

func main () {
populateClichesList ()

// From now on, this gorountine alone accesses the clichesList.
crudRequests = make ( chan * crudRequest , 8 )
go func () { // resource manager
for {
select {
case req := < - crudRequests :
if req . verb == GETALL {
req . confirm< - readAll ()
} else if req . verb == GETONE {
req . confirm< - readOne ( req . id )
} else if req . verb == POST {
req . confirm< - addPair ( req . cp )
} else if req . verb == PUT {
req . confirm< - editPair ( req . id , req . cliche , req . counter )
} else if req . verb == DELETE {
req . confirm< - deletePair ( req . id )
}
}
}()
startServer ()
}

func startServer () {
router := mux . NewRouter ()

// Dispatch map for CRUD operations.
router . HandleFunc ( "/" , ClichesAll ) . Methods ( "GET" )
router . HandleFunc ( "/cliches" , ClichesAll ) . Methods ( "GET" )
router . HandleFunc ( "/cliches/{id:[0-9]+}" , ClichesOne ) . Methods ( "GET" )

router . HandleFunc ( "/cliches" , ClichesCreate ) . Methods ( "POST" )
router . HandleFunc ( "/cliches/{id:[0-9]+}" , ClichesEdit ) . Methods ( "PUT" )
router . HandleFunc ( "/cliches/{id:[0-9]+}" , ClichesDelete ) . Methods ( "DELETE" )

http . Handle ( "/" , router ) // enable the router

// Start the server.
port := ":8888"
fmt . Println ( " \n Listening on port " + port )
http . ListenAndServe ( port , router ); // mux.Router now in play
}

// Return entire list to requester.
func readAll () string {
msg := " \n "
for _ , cliche := range clichesList {
next := strconv . Itoa ( cliche . Id ) + ": " + cliche . Cliche + "  " + cliche . Counter + " \n "
msg += next
}
return msg
}

// Return specified clichePair to requester.
func readOne ( id int ) string {
msg := " \n " + "Bad Id: " + strconv . Itoa ( id ) + " \n "

index := findCliche ( id )
if index > = 0 {
cliche := clichesList [ index ]
msg = " \n " + strconv . Itoa ( id ) + ": " + cliche . Cliche + "  " + cliche . Counter + " \n "
}
return msg
}

// Create a new clichePair and add to list
func addPair ( cp * clichePair ) string {
cp . Id = masterId
masterId ++
clichesList = append ( clichesList , cp )
return " \n Created: " + cp . Cliche + " " + cp . Counter + " \n "
}

// Edit an existing clichePair
func editPair ( id int , cliche string , counter string ) string {
msg := " \n " + "Bad Id: " + strconv . Itoa ( id ) + " \n "
index := findCliche ( id )
if index > = 0 {
clichesList [ index ] . Cliche = cliche
clichesList [ index ] . Counter = counter
msg = " \n Cliche edited: " + cliche + " " + counter + " \n "
}
return msg
}

// Delete a clichePair
func deletePair ( id int ) string {
idStr := strconv . Itoa ( id )
msg := " \n " + "Bad Id: " + idStr + " \n "
index := findCliche ( id )
if index > = 0 {
clichesList = append ( clichesList [: index ], clichesList [ index + 1 :] ... )
msg = " \n Cliche " + idStr + " deleted \n "
}
return msg
}

//*** utility functions
func findCliche ( id int ) int {
for i := 0 ; i < len ( clichesList ); i ++ {
if id == clichesList [ i ] . Id {
return i ;
}
}
return - 1 // not found
}

func getIdFromRequest ( req * http. Request ) int {
vars := mux . Vars ( req )
id , _ := strconv . Atoi ( vars [ "id" ])
return id
}

func getDataFromRequest ( req * http. Request ) ( string , string ) {
// Extract the user-provided data for the new clichePair
req . ParseForm ()
form := req . Form
cliche := form [ "cliche" ][ 0 ]    // 1st and only member of a list
counter := form [ "counter" ][ 0 ]  // ditto
return cliche , counter
}

func logIt ( msg string ) {
fmt . Println ( msg )
}

func populateClichesList () {
var cliches = [] string {
"Out of sight, out of mind." ,
"A penny saved is a penny earned." ,
"He who hesitates is lost." ,
}
var counterCliches = [] string {
"Absence makes the heart grow fonder." ,
"Penny-wise and dollar-foolish." ,
"Look before you leap." ,
}

for i := 0 ; i < len ( cliches ); i ++ {
cp := new ( clichePair )
cp . Id = masterId
masterId ++
cp . Cliche = cliches [ i ]
cp . Counter = counterCliches [ i ]
clichesList = append ( clichesList , cp )
}
}