package domain

import (
	"crypto/sha256"
	"fmt"
	"strconv"
	"time"
)

const (
	ResultDeliveryAlertAfter  = 5 * time.Minute
	ResultDeliveryReviewAfter = 30 * time.Minute
)

type IntegrityState string

const (
	IntegrityCertified  IntegrityState = "CERTIFIED"
	IntegritySuppressed IntegrityState = "SUPPRESSED"
	IntegrityReview     IntegrityState = "REVIEW"
)

type IntegrityEvidence struct {
	RosterAuthoritative     bool
	SimulationAuthoritative bool
	ResultAuthoritative     bool
	RegionalPlayFair        bool
	DeliveryAvailable       bool
}

// ClassifyIntegrity deliberately ignores DeliveryAvailable when deciding
// rating eligibility: a healthy match remains rated while the control plane
// is temporarily unable to acknowledge its result.
func ClassifyIntegrity(evidence IntegrityEvidence) IntegrityState {
	if !evidence.RosterAuthoritative || !evidence.SimulationAuthoritative || !evidence.ResultAuthoritative || !evidence.RegionalPlayFair {
		return IntegritySuppressed
	}
	return IntegrityCertified
}

var (
	ErrResultBinding  = fmt.Errorf("result workload binding rejected")
	ErrResultConflict = fmt.Errorf("conflicting result")
	ErrResultInvalid  = fmt.Errorf("invalid match result")
	ErrReceiptMissing = fmt.Errorf("result receipt not found")
)

// WorkloadBinding is the identity extracted and validated by the secure
// credential adapter. The domain compares every binding dimension recorded by
// allocation; a shared service-account class is not sufficient on its own.
type WorkloadBinding struct {
	Issuer        string
	Audience      string
	Namespace     string
	ServiceAcct   string
	PodUID        string
	GameServerUID string
	MatchID       string
	ServerID      string
}

type MatchResult struct {
	MatchID        string
	ServerID       string
	ResultNonce    string
	Team0Score     int
	Team1Score     int
	IntegrityState IntegrityState
}

type ResultReceipt struct {
	ResultID       string
	MatchID        string
	ResultNonce    string
	PayloadDigest  [32]byte
	IntegrityState IntegrityState
	ReceivedAt     time.Time
	CommittedAt    time.Time
}

type ResultStore struct {
	expected WorkloadBinding
	receipts map[string]ResultReceipt
}

func NewResultStore(expected WorkloadBinding) (*ResultStore, error) {
	if err := validateBinding(expected); err != nil {
		return nil, err
	}
	return &ResultStore{expected: expected, receipts: make(map[string]ResultReceipt)}, nil
}

// Submit is the durable-transaction boundary in miniature. Production code
// must persist the receipt, match transition, participant penalties/ratings,
// and outbox event atomically around this same decision.
func (s *ResultStore) Submit(resultID string, result MatchResult, binding WorkloadBinding, now time.Time) (ResultReceipt, bool, error) {
	if resultID == "" || !sameBinding(s.expected, binding) {
		return ResultReceipt{}, false, ErrResultBinding
	}
	if err := validateResult(s.expected, result); err != nil {
		return ResultReceipt{}, false, err
	}
	digest := resultDigest(result)
	if prior, ok := s.receipts[result.MatchID]; ok {
		if prior.ResultID == resultID && prior.PayloadDigest == digest {
			return prior, false, nil
		}
		return prior, false, ErrResultConflict
	}
	receipt := ResultReceipt{ResultID: resultID, MatchID: result.MatchID, ResultNonce: result.ResultNonce, PayloadDigest: digest, IntegrityState: result.IntegrityState, ReceivedAt: now}
	s.receipts[result.MatchID] = receipt
	return receipt, true, nil
}

// ResultAnnotation is the non-secret Agones spool representation. Its
// signature is checked by the workload-credential adapter before Reconcile;
// the digest check here prevents annotation/payload drift even after trust
// has been established.
type ResultAnnotation struct {
	ResultID      string
	Result        MatchResult
	PayloadDigest [32]byte
	Signature     []byte
}

func (s *ResultStore) Reconcile(annotation ResultAnnotation, verify func(ResultAnnotation) bool, binding WorkloadBinding, now time.Time) (ResultReceipt, bool, error) {
	if len(annotation.Signature) == 0 || verify == nil || !verify(annotation) || annotation.PayloadDigest != resultDigest(annotation.Result) {
		return ResultReceipt{}, false, ErrResultBinding
	}
	return s.Submit(annotation.ResultID, annotation.Result, binding, now)
}

func (s *ResultStore) Commit(resultID, matchID string, now time.Time) (ResultReceipt, error) {
	receipt, ok := s.receipts[matchID]
	if !ok || receipt.ResultID != resultID {
		return ResultReceipt{}, ErrReceiptMissing
	}
	if receipt.CommittedAt.IsZero() {
		receipt.CommittedAt = now
		s.receipts[matchID] = receipt
	}
	return receipt, nil
}

type DeliveryHealth string

const (
	DeliveryHealthy DeliveryHealth = "HEALTHY"
	DeliveryAlert   DeliveryHealth = "ALERT"
	DeliveryReview  DeliveryHealth = "REVIEW"
)

func DeliveryStatus(receipt ResultReceipt, now time.Time) DeliveryHealth {
	if !receipt.CommittedAt.IsZero() {
		return DeliveryHealthy
	}
	age := now.Sub(receipt.ReceivedAt)
	if age >= ResultDeliveryReviewAfter {
		return DeliveryReview
	}
	if age >= ResultDeliveryAlertAfter {
		return DeliveryAlert
	}
	return DeliveryHealthy
}

func RatingEligible(receipt ResultReceipt) bool {
	return receipt.IntegrityState == IntegrityCertified
}

func validateBinding(binding WorkloadBinding) error {
	if binding.Issuer == "" || binding.Audience == "" || binding.Namespace == "" || binding.ServiceAcct == "" || binding.PodUID == "" || binding.GameServerUID == "" || binding.MatchID == "" || binding.ServerID == "" {
		return ErrResultBinding
	}
	return nil
}

func sameBinding(a, b WorkloadBinding) bool { return a == b }

func validateResult(expected WorkloadBinding, result MatchResult) error {
	if result.MatchID != expected.MatchID || result.ServerID != expected.ServerID || len(result.ResultNonce) < 16 || len(result.ResultNonce) > 128 || result.Team0Score < 0 || result.Team1Score < 0 {
		return ErrResultInvalid
	}
	switch result.IntegrityState {
	case IntegrityCertified, IntegritySuppressed, IntegrityReview:
		return nil
	default:
		return ErrResultInvalid
	}
}

func resultDigest(result MatchResult) [32]byte {
	canonical := result.MatchID + "\x00" + result.ServerID + "\x00" + result.ResultNonce + "\x00" + strconv.Itoa(result.Team0Score) + "\x00" + strconv.Itoa(result.Team1Score) + "\x00" + string(result.IntegrityState)
	return sha256.Sum256([]byte(canonical))
}