package docproject

import (
	"context"
	"encoding/json"
	"errors"

	"chat-agent-system/internal/docgov"
	"chat-agent-system/internal/events"

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

// EventConsumer applies document.agent_version_committed onto ledger head pointers.
// Closures/producer already project in the approve/commit UoW; this path is idempotent no-replace.
type EventConsumer struct {
	Docs DocumentLookup
	Env  string
}

type DocumentLookup interface {
	GetDocument(ctx context.Context, docID string) (*docgov.DocumentRecord, error)
}

func (c *EventConsumer) HandleLease(ctx context.Context, lease events.Lease, tx pgx.Tx) error {
	if c == nil {
		return events.ErrUnknownConsumer
	}
	principal := events.ServicePrincipal{
		ID: "projection-" + c.Env, Environment: c.Env, Consumer: events.ConsumerProjection,
		Actions: []string{"projection.apply"},
	}
	if err := events.AuthorizePrincipal(principal, lease.Environment, lease.ProjectID, "projection.apply"); err != nil {
		return events.ErrQuarantine
	}
	if lease.EventName != events.EventVersionCommitted {
		return nil
	}
	docID := lease.Envelope.AggregateID
	versionNo := int(lease.Envelope.AggregateVersion)
	var payload map[string]any
	_ = json.Unmarshal(lease.Envelope.Payload, &payload)
	if payload != nil {
		if id, ok := payload["doc_id"].(string); ok && id != "" {
			docID = id
		}
		if v, ok := payload["version_no"].(float64); ok {
			versionNo = int(v)
		}
	}
	if c.Docs == nil || docID == "" {
		return events.ErrQuarantine
	}
	doc, err := c.Docs.GetDocument(ctx, docID)
	if err != nil || doc == nil {
		return events.ErrQuarantine
	}
	if doc.ProjectID != lease.ProjectID {
		return events.ErrQuarantine
	}
	var versionID, snapshotID int64
	var sha string
	err = tx.QueryRow(ctx, `
		SELECT v.id, COALESCE(v.head_snapshot_id,0), COALESCE(s.content_sha256,'')
		FROM document_versions v
		LEFT JOIN document_snapshots s ON s.id = v.head_snapshot_id
		WHERE v.doc_id=$1 AND v.version_no=$2
	`, docID, versionNo).Scan(&versionID, &snapshotID, &sha)
	if err != nil {
		return events.ErrQuarantine
	}
	tag, err := tx.Exec(ctx, `
		INSERT INTO event_projection_outcomes (source_event_id, doc_id, version_no, snapshot_id, applied)
		VALUES ($1,$2,$3,$4,false)
		ON CONFLICT (source_event_id) DO NOTHING
	`, lease.EventID, docID, versionNo, snapshotID)
	if err != nil {
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			return nil
		}
		return err
	}
	if tag.RowsAffected() == 0 {
		return nil
	}
	applied, err := (docgov.Repository{}).ProjectHeadNoReplace(ctx, tx, docID, versionID, snapshotID, versionNo, sha)
	if err != nil {
		return err
	}
	_, err = tx.Exec(ctx, `
		UPDATE event_projection_outcomes SET applied=$2, snapshot_id=$3 WHERE source_event_id=$1
	`, lease.EventID, applied, snapshotID)
	return err
}