package config

import (
	"errors"
	"fmt"
	"net"
	"os"
	"strconv"
	"time"
)

type Config struct {
	HTTPAddr             string
	MySQLDSN             string
	MaxOpen              int
	MaxIdle              int
	MetricsAddr          string
	WorkflowTickInterval time.Duration // WorkflowTickInterval Weave 持久化推进扫描间隔，范围100ms–1m。
	ScheduleTickInterval time.Duration // ScheduleTickInterval 计划扫描间隔，范围100ms–1m。
	RecoveryTickInterval time.Duration // RecoveryTickInterval 执行租约恢复扫描间隔，范围100ms–1m。
	RuntimeBatchLimit    int           // RuntimeBatchLimit 每个后台批次的候选上限，范围1–100。
	ShutdownTimeout      time.Duration // ShutdownTimeout 优雅排空和关闭窗口，范围1s–5m。
}

func Load() (Config, error) { return FromEnv(os.Getenv) }
func FromEnv(get func(string) string) (Config, error) {
	c := Config{
		HTTPAddr:             get("ORBIT_HTTP_ADDR"),
		MySQLDSN:             get("ORBIT_MYSQL_DSN"),
		MaxOpen:              20,
		MaxIdle:              5,
		MetricsAddr:          get("ORBIT_METRICS_ADDR"),
		WorkflowTickInterval: time.Second,
		ScheduleTickInterval: time.Second,
		RecoveryTickInterval: 2 * time.Second,
		RuntimeBatchLimit:    100,
		ShutdownTimeout:      10 * time.Second,
	}
	if c.HTTPAddr == "" {
		c.HTTPAddr = "127.0.0.1:8080"
	}
	if _, _, err := net.SplitHostPort(c.HTTPAddr); err != nil {
		return Config{}, errors.New("invalid ORBIT_HTTP_ADDR")
	}
	if c.MySQLDSN == "" {
		return Config{}, errors.New("ORBIT_MYSQL_DSN is required")
	}
	for _, field := range []struct {
		name string
		dst  *int
	}{{"ORBIT_DB_MAX_OPEN", &c.MaxOpen}, {"ORBIT_DB_MAX_IDLE", &c.MaxIdle}} {
		if raw := get(field.name); raw != "" {
			n, err := strconv.Atoi(raw)
			if err != nil || n < 0 {
				return Config{}, fmt.Errorf("%s must be a nonnegative integer", field.name)
			}
			*field.dst = n
		}
	}
	if c.MaxOpen <= 0 || c.MaxIdle > c.MaxOpen {
		return Config{}, errors.New("database pool requires 0 <= max_idle <= max_open and max_open > 0")
	}
	for _, field := range []struct {
		name string
		dst  *time.Duration
	}{{"ORBIT_WORKFLOW_TICK_INTERVAL", &c.WorkflowTickInterval}, {"ORBIT_SCHEDULE_TICK_INTERVAL", &c.ScheduleTickInterval}, {"ORBIT_RECOVERY_TICK_INTERVAL", &c.RecoveryTickInterval}} {
		if raw := get(field.name); raw != "" {
			d, err := time.ParseDuration(raw)
			if err != nil || d < 100*time.Millisecond || d > time.Minute {
				return Config{}, fmt.Errorf("%s must be a duration from 100ms to 1m", field.name)
			}
			*field.dst = d
		}
	}
	if raw := get("ORBIT_RUNTIME_BATCH_LIMIT"); raw != "" {
		n, err := strconv.Atoi(raw)
		if err != nil || n < 1 || n > 100 {
			return Config{}, errors.New("ORBIT_RUNTIME_BATCH_LIMIT must be an integer from 1 to 100")
		}
		c.RuntimeBatchLimit = n
	}
	if raw := get("ORBIT_SHUTDOWN_TIMEOUT"); raw != "" {
		d, err := time.ParseDuration(raw)
		if err != nil || d < time.Second || d > 5*time.Minute {
			return Config{}, errors.New("ORBIT_SHUTDOWN_TIMEOUT must be a duration from 1s to 5m")
		}
		c.ShutdownTimeout = d
	}
	if c.MetricsAddr != "" {
		_, port, err := net.SplitHostPort(c.MetricsAddr)
		n, parseErr := strconv.Atoi(port)
		if err != nil || parseErr != nil || n < 0 || n > 65535 {
			return Config{}, errors.New("invalid ORBIT_METRICS_ADDR")
		}
	}
	return c, nil
}