package testkit

import (
	"fmt"
	"sync"

	"galaxy/authsession/internal/domain/common"
	"galaxy/authsession/internal/ports"
)

// SequenceIDGenerator is a deterministic IDGenerator double that consumes
// queued identifiers before falling back to monotonic generated ids.
type SequenceIDGenerator struct {
	mu sync.Mutex

	// ChallengeIDs stores queued challenge identifiers returned by
	// NewChallengeID before generated ids are used.
	ChallengeIDs []common.ChallengeID

	// DeviceSessionIDs stores queued device-session identifiers returned by
	// NewDeviceSessionID before generated ids are used.
	DeviceSessionIDs []common.DeviceSessionID

	// ChallengeErr is returned directly from NewChallengeID when set.
	ChallengeErr error

	// DeviceSessionErr is returned directly from NewDeviceSessionID when set.
	DeviceSessionErr error

	ChallengePrefix     string
	DeviceSessionPrefix string
	nextChallengeNumber int
	nextSessionNumber   int
}

// NewChallengeID returns the next deterministic challenge identifier.
func (g *SequenceIDGenerator) NewChallengeID() (common.ChallengeID, error) {
	if g.ChallengeErr != nil {
		return "", g.ChallengeErr
	}

	g.mu.Lock()
	defer g.mu.Unlock()

	if len(g.ChallengeIDs) > 0 {
		id := g.ChallengeIDs[0]
		g.ChallengeIDs = g.ChallengeIDs[1:]
		if err := id.Validate(); err != nil {
			return "", err
		}
		return id, nil
	}

	g.nextChallengeNumber++
	prefix := g.ChallengePrefix
	if prefix == "" {
		prefix = "challenge-"
	}

	id := common.ChallengeID(fmt.Sprintf("%s%d", prefix, g.nextChallengeNumber))
	if err := id.Validate(); err != nil {
		return "", err
	}

	return id, nil
}

// NewDeviceSessionID returns the next deterministic device-session
// identifier.
func (g *SequenceIDGenerator) NewDeviceSessionID() (common.DeviceSessionID, error) {
	if g.DeviceSessionErr != nil {
		return "", g.DeviceSessionErr
	}

	g.mu.Lock()
	defer g.mu.Unlock()

	if len(g.DeviceSessionIDs) > 0 {
		id := g.DeviceSessionIDs[0]
		g.DeviceSessionIDs = g.DeviceSessionIDs[1:]
		if err := id.Validate(); err != nil {
			return "", err
		}
		return id, nil
	}

	g.nextSessionNumber++
	prefix := g.DeviceSessionPrefix
	if prefix == "" {
		prefix = "device-session-"
	}

	id := common.DeviceSessionID(fmt.Sprintf("%s%d", prefix, g.nextSessionNumber))
	if err := id.Validate(); err != nil {
		return "", err
	}

	return id, nil
}

var _ ports.IDGenerator = (*SequenceIDGenerator)(nil)