package main

import (
	"flag"
	"fmt"
	"io"
	"net/http"
	"os"
)

type iostreams struct {
	Err io.Writer
	Out io.Writer
}

type Opts struct {
	ConfigPath string
	IO         iostreams
	Log        func(string)
	Logf       func(string, ...interface{})
}

func main() {
	var configFlag = flag.String("config", "config.yml", "A path to a config file.")
	flag.Parse()
	io := iostreams{
		Err: os.Stderr,
		Out: os.Stdout,
	}
	opts := Opts{
		ConfigPath: *configFlag,
		IO:         io,
		// TODO use real logger
		Log: func(s string) {
			fmt.Fprintln(io.Out, s)
		},
		Logf: func(s string, args ...interface{}) {
			fmt.Fprintf(io.Out, s, args...)
		},
	}

	err := _main(opts)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed: %s", err)
	}
}

func _main(opts Opts) error {
	cfg, err := parseConfig(opts.ConfigPath)
	if err != nil {
		fmt.Fprintf(os.Stderr, "could not read config file '%s'", opts.ConfigPath)
		os.Exit(1)
	}

	setupAPI(opts, *cfg)

	// TODO TLS or SSL or something
	opts.Logf("starting server at %s:%d\n", cfg.Host, cfg.Port)
	if err := http.ListenAndServe(fmt.Sprintf("%s:%d", cfg.Host, cfg.Port), nil); err != nil {
		return fmt.Errorf("http server exited with error: %w", err)
	}

	return nil
}

func handler(opts Opts, cfg Config, f http.HandlerFunc) http.HandlerFunc {
	// TODO make this more real
	return func(w http.ResponseWriter, req *http.Request) {
		opts.Log(req.URL.Path)
		f(w, req)
	}
}

func setupAPI(opts Opts, cfg Config) {
	http.HandleFunc("/instance", handler(opts, cfg, func(w http.ResponseWriter, req *http.Request) {
		io.WriteString(w, cfg.InstanceName)
	}))
}