package main

import (
	"fmt"
	"net"
	"strconv"
	"strings"
)

type Config struct {
	Profile, Address, Database, Trace string
	Hosts                             map[string]bool
	Connections, Inflight             int
}

func loadConfig(get func(string) string) (Config, error) {
	c := Config{Profile: get("APP_PROFILE"), Address: get("LISTEN_ADDR"), Database: databaseURL(get("DATABASE_URL")), Trace: get("SQL_TRACE"), Hosts: map[string]bool{}}
	if c.Profile == "" {
		c.Profile = "production"
	}
	if c.Profile != "production" && c.Profile != "compat" {
		return c, fmt.Errorf("APP_PROFILE must be production or compat")
	}
	if c.Address == "" {
		c.Address = "127.0.0.1:18001"
	}
	if _, _, err := net.SplitHostPort(c.Address); err != nil {
		return c, fmt.Errorf("LISTEN_ADDR must be host:port")
	}
	for _, host := range strings.Split(get("ALLOWED_HOSTS"), ",") {
		host = strings.ToLower(strings.TrimSpace(host))
		if host == "" {
			continue
		}
		if strings.ContainsAny(host, "/*@ \t\r\n") {
			return c, fmt.Errorf("ALLOWED_HOSTS requires exact hostnames without wildcards")
		}
		c.Hosts[host] = true
	}
	if c.Profile == "production" && len(c.Hosts) == 0 {
		return c, fmt.Errorf("ALLOWED_HOSTS is required in production")
	}
	if c.Profile == "production" && c.Trace != "" {
		return c, fmt.Errorf("SQL_TRACE is only available in compat profile")
	}
	for _, item := range []struct {
		name     string
		target   *int
		def, max int
	}{
		{"DB_MAX_CONNS", &c.Connections, 8, 128}, {"MAX_INFLIGHT", &c.Inflight, 64, 4096},
	} {
		*item.target = item.def
		if raw := get(item.name); raw != "" {
			value, err := strconv.Atoi(raw)
			if err != nil || value < 1 || value > item.max {
				return c, fmt.Errorf("%s must be between 1 and %d", item.name, item.max)
			}
			*item.target = value
		}
	}
	return c, nil
}

func databaseURL(value string) string {
	if value == "" {
		return "dbname=assignment_harness_native"
	}
	return value
}