package memorylifecycle

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"

	"data-terminal-cloud/internal/audit"
	"data-terminal-cloud/internal/database"
	"data-terminal-cloud/internal/outbox"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

const deletedMemoryMarker = "[已按用户请求删除]"

type DeleteProcessor struct {
	pool  *pgxpool.Pool
	audit *audit.Repository
}

func NewDeleteProcessor(pool *pgxpool.Pool) (*DeleteProcessor, error) {
	if pool == nil {
		return nil, errors.New("database pool is required")
	}
	return &DeleteProcessor{pool: pool, audit: audit.NewRepository()}, nil
}

func (p *DeleteProcessor) Handle(ctx context.Context, event outbox.Event) error {
	return database.Transact(ctx, p.pool, func(tx pgx.Tx) error {
		var tenantID, memoryPublicID, status string
		err := tx.QueryRow(ctx, `SELECT tenant_id::text,public_id::text,status FROM curated_memory WHERE id=$1::uuid FOR UPDATE`, event.AggregateID).Scan(&tenantID, &memoryPublicID, &status)
		if errors.Is(err, pgx.ErrNoRows) || status == "DELETED" {
			return nil
		}
		if err != nil {
			return fmt.Errorf("load memory deletion: %w", err)
		}
		if status != "PENDING_DELETE" {
			return nil
		}
		var unresolvedProviderRefs int
		if err := tx.QueryRow(ctx, `SELECT count(*) FROM memory_index_entry WHERE memory_id=$1::uuid AND index_type='provider' AND provider_ref IS NOT NULL AND status<>'DELETED'`, event.AggregateID).Scan(&unresolvedProviderRefs); err != nil {
			return fmt.Errorf("check provider memory deletion: %w", err)
		}
		if unresolvedProviderRefs > 0 {
			return outbox.Retryable(errors.New("provider memory deletion has not reconciled"))
		}
		if _, err := tx.Exec(ctx, `UPDATE memory_index_entry SET embedding=NULL,status='DELETED',provider_ref=NULL,indexed_at=NULL,last_error=NULL,updated_at=now() WHERE memory_id=$1::uuid`, event.AggregateID); err != nil {
			return fmt.Errorf("delete memory indexes: %w", err)
		}
		digest := sha256.Sum256([]byte(deletedMemoryMarker))
		if _, err := tx.Exec(ctx, `UPDATE memory_version SET content=$2,content_digest=$3,change_reason=CASE WHEN COALESCE(change_reason,'')='' THEN 'user requested deletion' ELSE change_reason || '; user requested deletion' END WHERE memory_id=$1::uuid`, event.AggregateID, deletedMemoryMarker, hex.EncodeToString(digest[:])); err != nil {
			return fmt.Errorf("redact memory versions: %w", err)
		}
		if _, err := tx.Exec(ctx, `UPDATE curated_memory SET status='DELETED',deleted_at=now(),valid_to=COALESCE(valid_to,now()),version=version+1,updated_at=now() WHERE id=$1::uuid`, event.AggregateID); err != nil {
			return fmt.Errorf("complete memory deletion: %w", err)
		}
		return p.audit.Record(ctx, tx, audit.Event{TenantID: &tenantID, ActorType: "system", Action: "memory.delete.complete", ResourceType: "memory", ResourceID: &memoryPublicID, Result: "success", Detail: map[string]any{"local_index": "deleted", "database_content": "redacted"}})
	})
}