// package scgi contains a minimal gemini SCGI framework
package scgi

import (
    "net"
    "bufio"
    "strings"
    "strconv"
    "log"
)

// SCGIHeaders is a map representing the headers of an SCGI request.
type SCGIHeaders map[string]string


// HandlerFunc is the type for a function that will handle an SCGI request
type HandlerFunc func(net.Conn, SCGIHeaders) error


// handle gets an SCGI request, parses it, and then lets fn handle the response
func handle(c net.Conn, fn HandlerFunc) {
    defer c.Close() // Connection has to be closed for gemini
    reader := bufio.NewReader(c)
    hl, err := reader.ReadString(':') // SCGI Spec: First bytes until a ':' represent the header length
    if err != nil {
        c.Write([]byte("42" + err.Error()))
        log.Print(err.Error())
        return
    }
    l, err := strconv.Atoi(hl[:len(hl)-1]) // Strip the trailing :
    if err != nil {
        c.Write([]byte("42" + err.Error()))
        log.Print(err.Error())
        return
    }
    buf := make([]byte, l)
    _, err = reader.Read(buf)
    if err != nil {
        c.Write([]byte("42" + err.Error()))
        log.Print(err.Error())
        return
    }
    headerString := string(buf[:l])
    headerData := strings.Split(headerString, "\x00") // split on NULLs
    header := make(SCGIHeaders)
    // convert header data (a slice) to a map
    for i := 0; i < len(headerData); i +=2 {
        if headerData[i] != "" {
            header[headerData[i]] = headerData[i+1]
        }
    }
    err = fn(c, header)
    if err != nil {
        log.Print(err.Error())
        return
    }
}

// Serve runs a simple SCGI server on listener, handling requests with fn
func Serve(listener net.Listener, fn HandlerFunc) error {
    for {
        conn, err := listener.Accept()
        if err != nil {
            log.Print(err)
        }

        go handle(conn, fn)
    }
}