package lobby

import (
	"fmt"
	"time"
)

// Config configures auto-match robot substitution: how long an open game waits for a
// human opponent before a robot is substituted, and how often the reaper scans.
type Config struct {
	// RobotWait is the fixed minimum an open auto-match game waits for a human
	// opponent before it is eligible for robot substitution. Sourced from
	// BACKEND_LOBBY_ROBOT_WAIT.
	RobotWait time.Duration
	// RobotWaitJitter is a random extra wait in [0, RobotWaitJitter) added on top of
	// RobotWait per game, so the substitution time varies. Sourced from
	// BACKEND_LOBBY_ROBOT_WAIT_JITTER.
	RobotWaitJitter time.Duration
	// ReaperInterval is how often the reaper scans for open games due for a robot.
	// Sourced from BACKEND_LOBBY_REAPER_INTERVAL.
	ReaperInterval time.Duration
}

// DefaultConfig returns the matchmaking defaults: a guaranteed 90-second wait for a
// human plus up to 90 random seconds (90–180 s total) before a robot substitutes
// (docs/ARCHITECTURE.md §7), scanned every five seconds.
func DefaultConfig() Config {
	return Config{
		RobotWait:       90 * time.Second,
		RobotWaitJitter: 90 * time.Second,
		ReaperInterval:  5 * time.Second,
	}
}

// Validate reports whether the configuration is usable.
func (c Config) Validate() error {
	if c.RobotWait <= 0 {
		return fmt.Errorf("lobby: robot wait must be positive, got %s", c.RobotWait)
	}
	if c.RobotWaitJitter < 0 {
		return fmt.Errorf("lobby: robot wait jitter must not be negative, got %s", c.RobotWaitJitter)
	}
	if c.ReaperInterval <= 0 {
		return fmt.Errorf("lobby: reaper interval must be positive, got %s", c.ReaperInterval)
	}
	return nil
}