package allocator

import (
	"context"
	"fmt"
	"strconv"
	"time"

	"github.com/cosmic-clash/cosmic-clash/server/domain"
)

// MatchClaimSource is the durable allocator work queue. Implementations must
// lease a match before returning it and fence binding by allocation ID.
type MatchClaimSource interface {
	ClaimAllocatingMatch(context.Context, time.Time) (domain.AllocationRequest, bool, error)
	BindAllocatedMatch(context.Context, domain.Allocation) error
}

// Worker consumes one leased match at a time. Provider failures deliberately
// retain the lease: an HTTP/provider failure can be ambiguous after an external
// allocation, so releasing it could allocate two GameServers for one match.
type Worker struct {
	Claims  MatchClaimSource
	Service Service
	Now     func() time.Time
}

// RunOnce returns whether it found a claimed match. It never exposes an
// endpoint itself; Service first records the provider allocation durably and
// BindAllocatedMatch then attaches that already-recorded allocation to the
// fenced match claim.
func (w Worker) RunOnce(ctx context.Context) (bool, error) {
	if w.Claims == nil || w.Now == nil {
		return false, errNotConfigured
	}
	request, found, err := w.Claims.ClaimAllocatingMatch(ctx, w.Now())
	if err != nil || !found {
		return found, err
	}
	result, err := w.Service.Allocate(ctx, request, AllocationLabels(request))
	if err != nil {
		return true, fmt.Errorf("allocate claimed match %s: %w", request.MatchID, err)
	}
	if err := w.Claims.BindAllocatedMatch(ctx, result.Allocation); err != nil {
		return true, fmt.Errorf("bind allocated match %s: %w", request.MatchID, err)
	}
	return true, nil
}

// AllocationLabels are the compatibility selectors shared with the Fleet
// template. They are derived only from the durable match plan, never client
// input or mutable worker configuration.
func AllocationLabels(request domain.AllocationRequest) map[string]string {
	return map[string]string{
		"cosmic-clash.io/region":    request.Region,
		"cosmic-clash.io/build":     request.Build,
		"cosmic-clash.io/protocol":  strconv.Itoa(request.Protocol),
		"cosmic-clash.io/transport": request.Transport,
	}
}