// Demo runs a minimal two-agent ECT workflow: Agent A creates a root ECT,
// "sends" it to Agent B; Agent B verifies, appends to ledger, then creates
// a child ECT; verification runs with DAG validation against the ledger.
package main

import (
	"crypto/ecdsa"
	"fmt"
	"log"
	"time"

	"github.com/nennemann/ect-refimpl/go-lang/ect"
)

func main() {
	ledger := ect.NewMemoryLedger()
	now := time.Now()

	// Agent A: spec reviewer
	keyA, err := ect.GenerateKey()
	if err != nil {
		log.Fatal(err)
	}
	agentA := "spiffe://example.com/agent/spec-reviewer"
	agentB := "spiffe://example.com/agent/implementer"
	kidA := "agent-a-key"

	// 1) Agent A creates root ECT (task id = jti per spec)
	payloadA := &ect.Payload{
		Iss:         agentA,
		Aud:         []string{agentB},
		Iat:         now.Unix(),
		Exp:         now.Add(10 * time.Minute).Unix(),
		Jti:         "550e8400-e29b-41d4-a716-446655440001",
		Wid:         "wf-demo-001",
		ExecAct:     "review_requirements_spec",
		Par:         []string{},
		Pol:         "spec_review_policy_v2",
		PolDecision: ect.PolDecisionApproved,
	}
	ectA, err := ect.Create(payloadA, keyA, ect.CreateOptions{KeyID: kidA})
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Agent A created root ECT (jti=550e8400-..., review_requirements_spec)")

	// 2) Agent B verifies (no store for DAG on first ECT)
	resolveKey := func(kid string) (*ecdsa.PublicKey, error) {
		if kid == kidA {
			return &keyA.PublicKey, nil
		}
		return nil, nil
	}
	opts := ect.VerifyOptions{
		VerifierID:   agentB,
		ResolveKey:   resolveKey,
		Store:        ledger,
		Now:          now,
		IATMaxAge:    15 * time.Minute,
		IATMaxFuture: 30 * time.Second,
	}
	parsed, err := ect.Verify(ectA, opts)
	if err != nil {
		log.Fatal(err)
	}
	_, err = ledger.Append(ectA, parsed.Payload)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Agent B verified root ECT and appended to ledger")

	// 3) Agent B creates child ECT (par contains parent jti values per spec)
	keyB, _ := ect.GenerateKey()
	kidB := "agent-b-key"
	payloadB := &ect.Payload{
		Iss:         agentB,
		Aud:         []string{"spiffe://example.com/system/ledger"},
		Iat:         now.Unix() + 1,
		Exp:         now.Add(10 * time.Minute).Unix(),
		Jti:         "550e8400-e29b-41d4-a716-446655440002",
		Wid:         "wf-demo-001",
		ExecAct:     "implement_module",
		Par:         []string{"550e8400-e29b-41d4-a716-446655440001"},
		Pol:         "coding_standards_v3",
		PolDecision: ect.PolDecisionApproved,
	}
	ectB, err := ect.Create(payloadB, keyB, ect.CreateOptions{KeyID: kidB})
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Agent B created child ECT (jti=550e8400-...002, implement_module, par=[parent jti])")

	// 4) Verify child ECT with DAG (ledger has task-001)
	resolverB := ect.KeyResolver(func(kid string) (*ecdsa.PublicKey, error) {
		if kid == kidB {
			return &keyB.PublicKey, nil
		}
		if kid == kidA {
			return &keyA.PublicKey, nil
		}
		return nil, nil
	})
	optsB := ect.VerifyOptions{
		VerifierID:   "spiffe://example.com/system/ledger",
		ResolveKey:   resolverB,
		Store:        ledger,
		Now:          now.Add(2 * time.Second),
		IATMaxAge:    15 * time.Minute,
		IATMaxFuture: 30 * time.Second,
	}
	parsedB, err := ect.Verify(ectB, optsB)
	if err != nil {
		log.Fatal(err)
	}
	_, err = ledger.Append(ectB, parsedB.Payload)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Verified child ECT with DAG validation and appended to ledger")
	fmt.Printf("Ledger entries: %s (%s), %s (%s)\n", parsed.Payload.Jti, parsed.Payload.ExecAct, parsedB.Payload.Jti, parsedB.Payload.ExecAct)
}