package host

import (
	"context"

	"github.com/carlosframework/platform/internal/hostclaim"
	"github.com/carlosframework/platform/internal/regionname"
	"github.com/carlosframework/platform/internal/release"
)

// ClaimOriginProof implements moves' Proven contract. HomeRegion must come from
// the verified roster/placement binding, and Claims is the deployment store.
// Admission.NewGeneration is deliberately not evidence of admission.
type ClaimOriginProof struct {
	Claims             release.Store
	HomeRegion, Region string
}

func (p ClaimOriginProof) Proven(ctx context.Context, o hostclaim.Observed, _ hostclaim.Admission, generations []string) (map[string]bool, error) {
	if o.Absent || o.Claim == nil || o.Claim.Holder == nil || p.Region == "" {
		return nil, hostclaim.ErrWrongState
	}
	h := o.Claim.Holder
	regions := []string{p.Region}
	if p.HomeRegion != "" && regionname.PlacementRegion(p.HomeRegion) == p.HomeRegion && regionname.SameRegion(p.HomeRegion, p.Region, regionname.HomeRegion) {
		if p.Region == regionname.HomeRegion {
			regions = append(regions, p.HomeRegion)
		} else {
			regions = append(regions, regionname.HomeRegion)
		}
	}
	set := make([]hostclaim.OriginTuple, 0, len(regions)*len(generations))
	for _, generation := range generations {
		for _, region := range regions {
			set = append(set, hostclaim.OriginTuple{Incarnation: h.Incarnation, Location: h.Location, Region: region, Generation: generation})
		}
	}
	proven, err := hostclaim.AdmittedOrigins(ctx, p.Claims, o, set)
	if err != nil {
		return nil, err
	}
	result := make(map[string]bool, len(generations))
	for _, tuple := range set {
		result[tuple.Generation] = result[tuple.Generation] || proven[tuple]
	}
	return result, nil
}