package mint

import (
	"fmt"
	"log"
	"os"
	"strings"
)

// We use this environment variable to control logging.  It should be a
// comma-separated list of log tags (see below) or "*" to enable all logging.
const logConfigVar = "MINT_LOG"

// Pre-defined log types
const (
	logTypeCrypto      = "crypto"
	logTypeHandshake   = "handshake"
	logTypeNegotiation = "negotiation"
	logTypeIO          = "io"
	logTypeFrameReader = "frame"
	logTypeVerbose     = "verbose"
)

var (
	logFunction = log.Printf
	logAll      = false
	logSettings = map[string]bool{}
)

func init() {
	parseLogEnv(os.Environ())
}

func parseLogEnv(env []string) {
	for _, stmt := range env {
		if strings.HasPrefix(stmt, logConfigVar+"=") {
			val := stmt[len(logConfigVar)+1:]

			if val == "*" {
				logAll = true
			} else {
				for _, t := range strings.Split(val, ",") {
					logSettings[t] = true
				}
			}
		}
	}
}

func logf(tag string, format string, args ...interface{}) {
	if logAll || logSettings[tag] {
		fullFormat := fmt.Sprintf("[%s] %s", tag, format)
		logFunction(fullFormat, args...)
	}
}