package httpapi

import (
	"context"
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/dtoro/oikos/internal/db"
	"github.com/dtoro/oikos/internal/db/sqlcgen"
	"github.com/dtoro/oikos/internal/domain"
	"github.com/dtoro/oikos/internal/httpapi/gen"
	"github.com/dtoro/oikos/internal/observability"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

const (
	defaultLimit = 50
	maxLimit     = 200
	graphNodeCap = 500
)

func clampLimit(l *int) int {
	if l == nil {
		return defaultLimit
	}
	if *l < 1 {
		return 1
	}
	if *l > maxLimit {
		return maxLimit
	}
	return *l
}

// resolveEntityID resolves a UUID-or-slug path/query value to the entity UUID.
func (s *Server) resolveEntityID(ctx context.Context, idOrSlug string) (uuid.UUID, error) {
	if id, err := uuid.Parse(idOrSlug); err == nil {
		var found uuid.UUID
		err := s.pool.QueryRow(ctx, "SELECT id FROM entities WHERE id = $1", id).Scan(&found)
		if err == pgx.ErrNoRows {
			return uuid.Nil, fmt.Errorf("%w: %s", domain.ErrNotFound, idOrSlug)
		}
		return found, err
	}
	var id uuid.UUID
	err := s.pool.QueryRow(ctx, "SELECT id FROM entities WHERE slug = $1", idOrSlug).Scan(&id)
	if err == pgx.ErrNoRows {
		return uuid.Nil, fmt.Errorf("%w: %s", domain.ErrNotFound, idOrSlug)
	}
	return id, err
}

// entityCols requires the entities table to be aliased as `e`.
const entityCols = `e.id, e.slug, e.type, e.name, e.state, e.attributes,
                    e.maintenance_until, e.version, e.created_at, e.updated_at`

func scanEntity(row pgx.Row) (gen.Entity, error) {
	var e gen.Entity
	var state *string
	var attrsJSON []byte
	var maint *time.Time
	err := row.Scan(&e.Id, &e.Slug, &e.Type, &e.Name, &state, &attrsJSON,
		&maint, &e.Version, &e.CreatedAt, &e.UpdatedAt)
	if err != nil {
		return e, err
	}
	e.State = state
	e.MaintenanceUntil = maint
	var attrs map[string]any
	if len(attrsJSON) > 0 && json.Unmarshal(attrsJSON, &attrs) == nil && len(attrs) > 0 {
		e.Attributes = &attrs
	}
	return e, nil
}

// ─── Entities ─────────────────────────────────────────────────────────

func (s *Server) ListEntities(ctx context.Context, req gen.ListEntitiesRequestObject) (gen.ListEntitiesResponseObject, error) {
	limit := clampLimit(req.Params.Limit)

	// Type filter includes descendants via the parent hierarchy (R3-1).
	query := `
		WITH RECURSIVE tt AS (
			SELECT name FROM entity_types WHERE $1::text IS NULL OR name = $1
			UNION
			SELECT et.name FROM entity_types et JOIN tt ON et.parent_type = tt.name
			WHERE $1::text IS NOT NULL
		)
		SELECT ` + entityCols + ` FROM entities e
		JOIN entity_types et ON et.name = e.type
		WHERE e.type IN (SELECT name FROM tt)
		  AND ($2::text IS NULL OR e.state = $2)
		  AND ($3::text IS NULL OR et.domain = $3)
		  AND ($4::text IS NULL OR et.layer = $4)
		  AND ($5::text IS NULL OR e.slug ILIKE '%'||$5||'%' OR e.name ILIKE '%'||$5||'%')
		  AND ($6::text IS NULL OR e.slug > $6)
		ORDER BY e.slug
		LIMIT $7`

	rows, err := s.pool.Query(ctx, query,
		req.Params.Type, req.Params.State, req.Params.Domain, req.Params.Layer,
		req.Params.Q, req.Params.Cursor, limit+1)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var items []gen.Entity
	for rows.Next() {
		e, err := scanEntity(rows)
		if err != nil {
			return nil, err
		}
		items = append(items, e)
	}
	if rows.Err() != nil {
		return nil, rows.Err()
	}

	var next *string
	if len(items) > limit {
		items = items[:limit]
		next = &items[len(items)-1].Slug
	}
	if items == nil {
		items = []gen.Entity{}
	}
	return gen.ListEntities200JSONResponse{Items: items, NextCursor: next}, nil
}

func (s *Server) GetEntity(ctx context.Context, req gen.GetEntityRequestObject) (gen.GetEntityResponseObject, error) {
	id, err := s.resolveEntityID(ctx, req.Id)
	if err != nil {
		return nil, err
	}
	e, err := scanEntity(s.pool.QueryRow(ctx,
		"SELECT "+entityCols+" FROM entities e WHERE e.id = $1", id))
	if err != nil {
		return nil, err
	}
	return gen.GetEntity200JSONResponse{
		Body:    e,
		Headers: gen.GetEntity200ResponseHeaders{ETag: `"` + strconv.Itoa(e.Version) + `"`},
	}, nil
}

func (s *Server) GetEntityRelations(ctx context.Context, req gen.GetEntityRelationsRequestObject) (gen.GetEntityRelationsResponseObject, error) {
	id, err := s.resolveEntityID(ctx, req.Id)
	if err != nil {
		return nil, err
	}
	dir := "both"
	if req.Params.Direction != nil {
		dir = string(*req.Params.Direction)
	}
	rows, err := s.pool.Query(ctx, `
		SELECT se.slug, te.slug, r.type, r.attributes, r.valid_from, r.valid_to
		FROM relationships r
		JOIN entities se ON se.id = r.source_id
		JOIN entities te ON te.id = r.target_id
		WHERE r.valid_to IS NULL
		  AND (($3 IN ('out','both') AND r.source_id = $1)
		    OR ($3 IN ('in','both')  AND r.target_id = $1))
		  AND ($2::text IS NULL OR r.type = $2)
		ORDER BY r.type, se.slug, te.slug`,
		id, req.Params.RelType, dir)
	if err != nil {
		return nil, err
	}
	items, err := scanRelationships(rows)
	if err != nil {
		return nil, err
	}
	return gen.GetEntityRelations200JSONResponse{Items: items}, nil
}

func scanRelationships(rows pgx.Rows) ([]gen.Relationship, error) {
	defer rows.Close()
	items := []gen.Relationship{}
	for rows.Next() {
		var rel gen.Relationship
		var attrsJSON []byte
		if err := rows.Scan(&rel.Source, &rel.Target, &rel.Type,
			&attrsJSON, &rel.ValidFrom, &rel.ValidTo); err != nil {
			return nil, err
		}
		var attrs map[string]any
		if len(attrsJSON) > 0 && json.Unmarshal(attrsJSON, &attrs) == nil && len(attrs) > 0 {
			rel.Attributes = &attrs
		}
		items = append(items, rel)
	}
	return items, rows.Err()
}

func (s *Server) GetBlastRadius(ctx context.Context, req gen.GetBlastRadiusRequestObject) (gen.GetBlastRadiusResponseObject, error) {
	id, err := s.resolveEntityID(ctx, req.Id)
	if err != nil {
		return nil, err
	}
	depth := 3
	if req.Params.Depth != nil {
		depth = *req.Params.Depth
	}
	rows, err := s.pool.Query(ctx, `
		SELECT `+entityCols+`, b.depth
		FROM blast_radius($1, $2) b
		JOIN entities e ON e.id = b.entity_id
		ORDER BY b.depth, e.slug`, id, depth)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	resp := gen.GetBlastRadius200JSONResponse{Items: []struct {
		Depth  int        `json:"depth"`
		Entity gen.Entity `json:"entity"`
	}{}}
	for rows.Next() {
		var e gen.Entity
		var state *string
		var attrsJSON []byte
		var maint *time.Time
		var d int
		if err := rows.Scan(&e.Id, &e.Slug, &e.Type, &e.Name, &state, &attrsJSON,
			&maint, &e.Version, &e.CreatedAt, &e.UpdatedAt, &d); err != nil {
			return nil, err
		}
		e.State = state
		e.MaintenanceUntil = maint
		var attrs map[string]any
		if len(attrsJSON) > 0 && json.Unmarshal(attrsJSON, &attrs) == nil && len(attrs) > 0 {
			e.Attributes = &attrs
		}
		resp.Items = append(resp.Items, struct {
			Depth  int        `json:"depth"`
			Entity gen.Entity `json:"entity"`
		}{Depth: d, Entity: e})
	}
	return resp, rows.Err()
}

func (s *Server) GetGraph(ctx context.Context, req gen.GetGraphRequestObject) (gen.GetGraphResponseObject, error) {
	depth := 2
	if req.Params.Depth != nil {
		depth = *req.Params.Depth
	}

	var nodes []gen.Entity
	var err error
	truncated := false

	if req.Params.Root != nil && *req.Params.Root != "" {
		rootID, rerr := s.resolveEntityID(ctx, *req.Params.Root)
		if rerr != nil {
			return nil, rerr
		}
		nodes, err = s.queryEntities(ctx, `
			SELECT `+entityCols+`
			FROM blast_radius($1, $2, $3) b JOIN entities e ON e.id = b.entity_id
			ORDER BY e.slug`, rootID, depth, req.Params.RelType)
	} else {
		nodes, err = s.queryEntities(ctx, `
			SELECT `+entityCols+` FROM entities e ORDER BY e.slug LIMIT $1`,
			graphNodeCap+1)
		if err == nil && len(nodes) > graphNodeCap {
			nodes = nodes[:graphNodeCap]
			truncated = true
		}
	}
	if err != nil {
		return nil, err
	}

	ids := make([]uuid.UUID, len(nodes))
	for i, n := range nodes {
		ids[i] = uuid.UUID(n.Id)
	}
	rows, err := s.pool.Query(ctx, `
		SELECT se.slug, te.slug, r.type, r.attributes, r.valid_from, r.valid_to
		FROM relationships r
		JOIN entities se ON se.id = r.source_id
		JOIN entities te ON te.id = r.target_id
		WHERE r.valid_to IS NULL
		  AND r.source_id = ANY($1) AND r.target_id = ANY($1)
		  AND ($2::text[] IS NULL OR r.type = ANY($2))
		ORDER BY r.type, se.slug, te.slug`, ids, req.Params.RelType)
	if err != nil {
		return nil, err
	}
	edges, err := scanRelationships(rows)
	if err != nil {
		return nil, err
	}

	resp := gen.GetGraph200JSONResponse{Nodes: nodes, Edges: edges}
	if truncated {
		resp.Truncated = &truncated
	}
	return resp, nil
}

func (s *Server) queryEntities(ctx context.Context, query string, args ...any) ([]gen.Entity, error) {
	rows, err := s.pool.Query(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	items := []gen.Entity{}
	for rows.Next() {
		e, err := scanEntity(rows)
		if err != nil {
			return nil, err
		}
		items = append(items, e)
	}
	return items, rows.Err()
}

// ─── Ontology ─────────────────────────────────────────────────────────

func (s *Server) GetOntology(ctx context.Context, req gen.GetOntologyRequestObject) (gen.GetOntologyResponseObject, error) {
	resp := gen.GetOntology200JSONResponse{
		EntityTypes:       []gen.EntityType{},
		RelationshipTypes: []gen.RelationshipType{},
		Lifecycles:        []gen.LifecycleDef{},
	}

	rows, err := s.pool.Query(ctx, `
		SELECT name, parent_type, is_abstract, domain, layer, description,
		       lifecycle_id, attribute_schema, schema_version, status
		FROM entity_types ORDER BY name`)
	if err != nil {
		return nil, err
	}
	for rows.Next() {
		var et gen.EntityType
		var schemaVersion int
		var schemaJSON []byte
		if err := rows.Scan(&et.Name, &et.ParentType, &et.IsAbstract, &et.Domain,
			&et.Layer, &et.Description, &et.LifecycleId, &schemaJSON,
			&schemaVersion, &et.Status); err != nil {
			rows.Close()
			return nil, err
		}
		et.SchemaVersion = &schemaVersion
		var schema map[string]any
		if len(schemaJSON) > 0 && json.Unmarshal(schemaJSON, &schema) == nil && schema != nil {
			et.AttributeSchema = &schema
		}
		resp.EntityTypes = append(resp.EntityTypes, et)
	}
	rows.Close()
	if rows.Err() != nil {
		return nil, rows.Err()
	}

	rows, err = s.pool.Query(ctx, `
		SELECT name, inverse, source_type, target_type, cardinality, description
		FROM relationship_types ORDER BY name`)
	if err != nil {
		return nil, err
	}
	for rows.Next() {
		var rt gen.RelationshipType
		if err := rows.Scan(&rt.Name, &rt.Inverse, &rt.SourceType, &rt.TargetType,
			&rt.Cardinality, &rt.Description); err != nil {
			rows.Close()
			return nil, err
		}
		resp.RelationshipTypes = append(resp.RelationshipTypes, rt)
	}
	rows.Close()
	if rows.Err() != nil {
		return nil, rows.Err()
	}

	rows, err = s.pool.Query(ctx, `
		SELECT id, states, default_state, terminal_states, transitions
		FROM lifecycle_defs ORDER BY id`)
	if err != nil {
		return nil, err
	}
	for rows.Next() {
		var lc gen.LifecycleDef
		var terminal []string
		var transJSON []byte
		if err := rows.Scan(&lc.Id, &lc.States, &lc.DefaultState, &terminal, &transJSON); err != nil {
			rows.Close()
			return nil, err
		}
		lc.TerminalStates = &terminal
		if err := json.Unmarshal(transJSON, &lc.Transitions); err != nil {
			rows.Close()
			return nil, fmt.Errorf("lifecycle %s transitions: %w", lc.Id, err)
		}
		resp.Lifecycles = append(resp.Lifecycles, lc)
	}
	rows.Close()
	return resp, rows.Err()
}

// ─── Signals ──────────────────────────────────────────────────────────

func (s *Server) ListSignals(ctx context.Context, req gen.ListSignalsRequestObject) (gen.ListSignalsResponseObject, error) {
	limit := clampLimit(req.Params.Limit)
	rows, err := s.pool.Query(ctx, `
		SELECT sig.entity_id, se.slug, sig.kind, sig.severity, sig.state,
		       te.slug, sig.check_id::text, sig.evidence, sig.likely_cause,
		       sig.occurrence_count, sig.flap_count, sig.hold_down_until,
		       sig.mute_until, sig.first_seen_at, sig.last_seen_at
		FROM signals sig
		JOIN entities se ON se.id = sig.entity_id
		LEFT JOIN entities te ON te.id = sig.target_entity_id
		WHERE ($1::text IS NULL OR sig.state = $1)
		  AND ($2::text IS NULL OR sig.severity = $2)
		  AND ($3::text IS NULL OR te.slug = $3)
		  AND ($4::text IS NULL OR sig.kind = $4)
		  AND ($5::text IS NULL OR se.slug > $5)
		ORDER BY se.slug
		LIMIT $6`,
		req.Params.State, (*string)(req.Params.Severity), req.Params.EntityId,
		req.Params.Kind, req.Params.Cursor, limit+1)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	items := []gen.Signal{}
	for rows.Next() {
		var sig gen.Signal
		var flap int
		if err := rows.Scan(&sig.Id, &sig.Slug, &sig.Kind, &sig.Severity, &sig.State,
			&sig.Target, &sig.CheckId, &sig.Evidence, &sig.LikelyCause,
			&sig.OccurrenceCount, &flap, &sig.HoldDownUntil,
			&sig.MuteUntil, &sig.FirstSeenAt, &sig.LastSeenAt); err != nil {
			return nil, err
		}
		sig.FlapCount = &flap
		items = append(items, sig)
	}
	if rows.Err() != nil {
		return nil, rows.Err()
	}

	var next *string
	if len(items) > limit {
		items = items[:limit]
		next = &items[len(items)-1].Slug
	}
	return gen.ListSignals200JSONResponse{Items: items, NextCursor: next}, nil
}

// ─── Observability + system ───────────────────────────────────────────

func (s *Server) GetFleetHealth(ctx context.Context, req gen.GetFleetHealthRequestObject) (gen.GetFleetHealthResponseObject, error) {
	resp := gen.GetFleetHealth200JSONResponse{}
	resp.Entities = []struct {
		Health      gen.HealthSummaryEntitiesHealth `json:"health"`
		LastCheckAt *time.Time                      `json:"last_check_at"`
		Slug        string                          `json:"slug"`
		Trend       *gen.HealthSummaryEntitiesTrend `json:"trend"`
		Type        string                          `json:"type"`
	}{}

	rows, err := s.pool.Query(ctx, `
		SELECT e.slug, e.type, st.health, st.last_check_at
		FROM entity_status st JOIN entities e ON e.id = st.entity_id
		ORDER BY e.slug`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	for rows.Next() {
		var slug, typ, health string
		var lastCheck *time.Time
		if err := rows.Scan(&slug, &typ, &health, &lastCheck); err != nil {
			return nil, err
		}
		switch health {
		case "healthy":
			resp.Summary.Healthy++
		case "degraded":
			resp.Summary.Degraded++
		case "down":
			resp.Summary.Down++
		default:
			resp.Summary.Unknown++
		}
		resp.Entities = append(resp.Entities, struct {
			Health      gen.HealthSummaryEntitiesHealth `json:"health"`
			LastCheckAt *time.Time                      `json:"last_check_at"`
			Slug        string                          `json:"slug"`
			Trend       *gen.HealthSummaryEntitiesTrend `json:"trend"`
			Type        string                          `json:"type"`
		}{
			Health:      gen.HealthSummaryEntitiesHealth(health),
			LastCheckAt: lastCheck,
			Slug:        slug,
			Type:        typ,
		})
	}
	return resp, rows.Err()
}

func (s *Server) ExportSeeds(ctx context.Context, req gen.ExportSeedsRequestObject) (gen.ExportSeedsResponseObject, error) {
	exports, err := db.ExportToYAML(ctx, s.pool)
	if err != nil {
		return nil, err
	}
	return gen.ExportSeeds200JSONResponse{
		Ontology:  string(exports["ontology.yaml"]),
		Inventory: string(exports["inventory.yaml"]),
		Policy:    string(exports["policy.yaml"]),
	}, nil
}

// ─── Signal mutations ────────────────────────────────────────────────

func (s *Server) AckSignal(ctx context.Context, req gen.AckSignalRequestObject) (gen.AckSignalResponseObject, error) {
	id, err := s.resolveEntityID(ctx, req.Id)
	if err != nil {
		return nil, err
	}
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)

	var sig gen.Signal
	err = tx.QueryRow(ctx, `
		UPDATE signals SET state = 'acknowledged', updated_at = now()
		WHERE entity_id = $1 AND state IN ('raised','failed')
		RETURNING entity_id, (SELECT slug FROM entities WHERE id = $1),
		          kind, severity, 'acknowledged',
		          (SELECT slug FROM entities WHERE id = target_entity_id),
		          check_id::text, evidence, likely_cause,
		          occurrence_count, flap_count, hold_down_until,
		          mute_until, first_seen_at, last_seen_at`,
		id).Scan(&sig.Id, &sig.Slug, &sig.Kind, &sig.Severity, &sig.State,
		&sig.Target, &sig.CheckId, &sig.Evidence, &sig.LikelyCause,
		&sig.OccurrenceCount, &sig.FlapCount, &sig.HoldDownUntil,
		&sig.MuteUntil, &sig.FirstSeenAt, &sig.LastSeenAt)
	if err != nil {
		if err == pgx.ErrNoRows {
			return nil, fmt.Errorf("%w: signal %s not in a state that can be acknowledged", domain.ErrInvalidTransition, req.Id)
		}
		return nil, err
	}
	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}
	return gen.AckSignal200JSONResponse{gen.SignalUpdatedJSONResponse(sig)}, nil
}

func (s *Server) ResolveSignal(ctx context.Context, req gen.ResolveSignalRequestObject) (gen.ResolveSignalResponseObject, error) {
	id, err := s.resolveEntityID(ctx, req.Id)
	if err != nil {
		return nil, err
	}
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)

	var sig gen.Signal
	err = tx.QueryRow(ctx, `
		UPDATE signals SET state = 'resolved', updated_at = now()
		WHERE entity_id = $1 AND state IN ('raised','acknowledged','acting','failed')
		RETURNING entity_id, (SELECT slug FROM entities WHERE id = $1),
		          kind, severity, 'resolved',
		          (SELECT slug FROM entities WHERE id = target_entity_id),
		          check_id::text, evidence, likely_cause,
		          occurrence_count, flap_count, hold_down_until,
		          mute_until, first_seen_at, last_seen_at`,
		id).Scan(&sig.Id, &sig.Slug, &sig.Kind, &sig.Severity, &sig.State,
		&sig.Target, &sig.CheckId, &sig.Evidence, &sig.LikelyCause,
		&sig.OccurrenceCount, &sig.FlapCount, &sig.HoldDownUntil,
		&sig.MuteUntil, &sig.FirstSeenAt, &sig.LastSeenAt)
	if err != nil {
		if err == pgx.ErrNoRows {
			return nil, fmt.Errorf("%w: signal %s not in a state that can be resolved", domain.ErrInvalidTransition, req.Id)
		}
		return nil, err
	}
	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}
	return gen.ResolveSignal200JSONResponse{gen.SignalUpdatedJSONResponse(sig)}, nil
}

func (s *Server) MuteSignal(ctx context.Context, req gen.MuteSignalRequestObject) (gen.MuteSignalResponseObject, error) {
	id, err := s.resolveEntityID(ctx, req.Id)
	if err != nil {
		return nil, err
	}
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)

	var sig gen.Signal
	err = tx.QueryRow(ctx, `
		UPDATE signals SET state = 'muted', mute_until = $2, updated_at = now()
		WHERE entity_id = $1 AND state IN ('raised','acknowledged')
		RETURNING entity_id, (SELECT slug FROM entities WHERE id = $1),
		          kind, severity, 'muted',
		          (SELECT slug FROM entities WHERE id = target_entity_id),
		          check_id::text, evidence, likely_cause,
		          occurrence_count, flap_count, hold_down_until,
		          mute_until, first_seen_at, last_seen_at`,
		id, req.Body.MuteUntil).Scan(&sig.Id, &sig.Slug, &sig.Kind, &sig.Severity, &sig.State,
		&sig.Target, &sig.CheckId, &sig.Evidence, &sig.LikelyCause,
		&sig.OccurrenceCount, &sig.FlapCount, &sig.HoldDownUntil,
		&sig.MuteUntil, &sig.FirstSeenAt, &sig.LastSeenAt)
	if err != nil {
		if err == pgx.ErrNoRows {
			return nil, fmt.Errorf("%w: signal %s not in a state that can be muted", domain.ErrInvalidTransition, req.Id)
		}
		return nil, err
	}
	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}
	return gen.MuteSignal200JSONResponse{gen.SignalUpdatedJSONResponse(sig)}, nil
}

// ─── Observability reads ─────────────────────────────────────────────

func (s *Server) QueryEvents(ctx context.Context, req gen.QueryEventsRequestObject) (gen.QueryEventsResponseObject, error) {
	limit := clampLimit(req.Params.Limit)
	var eventType, entityID, severity, correlationID *string
	if req.Params.Type != nil {
		eventType = req.Params.Type
	}
	if req.Params.EntityId != nil {
		entityID = req.Params.EntityId
	}
	if req.Params.Severity != nil {
		severity = req.Params.Severity
	}
	if req.Params.CorrelationId != nil {
		correlationID = req.Params.CorrelationId
	}

	rows, err := s.pool.Query(ctx, `
		SELECT id, ts, type, entity_id::text, severity, source, data, correlation_id
		FROM events
		WHERE ($1::text IS NULL OR type = $1)
		  AND ($2::text IS NULL OR entity_id::text = $2)
		  AND ($3::text IS NULL OR severity = $3)
		  AND ($4::text IS NULL OR correlation_id = $4)
		  AND ($5::timestamptz IS NULL OR ts >= $5)
		  AND ($6::timestamptz IS NULL OR ts <= $6)
		ORDER BY ts DESC
		LIMIT $7`,
		eventType, entityID, severity, correlationID, req.Params.From, req.Params.To, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	items := []gen.Event{}
	for rows.Next() {
		var e gen.Event
		var dataBytes []byte
		var entID, corrID *string
		if err := rows.Scan(&e.Id, &e.Ts, &e.Type, &entID, &e.Severity, &e.Source, &dataBytes, &corrID); err != nil {
			return nil, err
		}
		e.EntityId = entID
		e.CorrelationId = corrID
		var data map[string]any
		if json.Unmarshal(dataBytes, &data) == nil {
			e.Data = &data
		}
		items = append(items, e)
	}
	return gen.QueryEvents200JSONResponse{Items: items}, rows.Err()
}

func (s *Server) QueryAudit(ctx context.Context, req gen.QueryAuditRequestObject) (gen.QueryAuditResponseObject, error) {
	limit := clampLimit(req.Params.Limit)
	var actorType, actorID, action, entityID, correlationID *string
	if req.Params.ActorType != nil {
		actorType = req.Params.ActorType
	}
	if req.Params.ActorId != nil {
		actorID = req.Params.ActorId
	}
	if req.Params.Action != nil {
		action = req.Params.Action
	}
	if req.Params.EntityId != nil {
		entityID = req.Params.EntityId
	}
	if req.Params.CorrelationId != nil {
		correlationID = req.Params.CorrelationId
	}

	rows, err := s.pool.Query(ctx, `
		SELECT id, ts, actor_type, actor_id::text, action, entity_id::text,
		       method, path, status_code, detail, source_ip, correlation_id
		FROM audit_log
		WHERE ($1::text IS NULL OR actor_type = $1)
		  AND ($2::text IS NULL OR actor_id::text = $2)
		  AND ($3::text IS NULL OR action = $3)
		  AND ($4::text IS NULL OR entity_id::text = $4)
		  AND ($5::text IS NULL OR correlation_id = $5)
		  AND ($6::timestamptz IS NULL OR ts >= $6)
		  AND ($7::timestamptz IS NULL OR ts <= $7)
		ORDER BY ts DESC
		LIMIT $8`,
		actorType, actorID, action, entityID, correlationID, req.Params.From, req.Params.To, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	items := []gen.AuditEntry{}
	for rows.Next() {
		var a gen.AuditEntry
		var detailBytes []byte
		var actID, entID, method, path, sourceIP, corrID *string
		var statusCode *int
		if err := rows.Scan(&a.Id, &a.Ts, &a.ActorType, &actID, &a.Action, &entID,
			&method, &path, &statusCode, &detailBytes, &sourceIP, &corrID); err != nil {
			return nil, err
		}
		a.ActorId = actID
		a.EntityId = entID
		a.Method = method
		a.Path = path
		a.StatusCode = statusCode
		a.SourceIp = sourceIP
		a.CorrelationId = corrID
		var detail map[string]any
		if json.Unmarshal(detailBytes, &detail) == nil {
			a.Detail = &detail
		}
		items = append(items, a)
	}
	return gen.QueryAudit200JSONResponse{Items: items}, rows.Err()
}

// ─── Entity mutations ──────────────────────────────────────────────

func (s *Server) CreateEntity(ctx context.Context, req gen.CreateEntityRequestObject) (gen.CreateEntityResponseObject, error) {
	if req.Body == nil {
		return nil, fmt.Errorf("%w: request body is required", domain.ErrInvalidInput)
	}

	// Check idempotency if a key was provided.
	actor := "operator"
	var bodyHash string
	if req.Params.IdempotencyKey != nil && *req.Params.IdempotencyKey != "" {
		key := *req.Params.IdempotencyKey
		q := sqlcgen.New(s.pool)
		cached, err := q.GetIdempotentResponse(ctx, sqlcgen.GetIdempotentResponseParams{
			Actor: actor,
			Key:   key,
		})
		if err == nil {
			// Verify the request body hasn't changed.
			bodyJSON, _ := json.Marshal(req.Body)
			bodyHash = fmt.Sprintf("%x", sha256.Sum256(bodyJSON))
			if cached.RequestHash != bodyHash {
				return nil, fmt.Errorf("%w: idempotency key %s used with different request body", domain.ErrConflict, key)
			}
			// Replay the cached response.
			if cached.ResponseCode != nil && *cached.ResponseCode == 201 {
				var entity gen.Entity
				if len(cached.ResponseBody) > 0 {
					if err := json.Unmarshal(cached.ResponseBody, &entity); err != nil {
						return nil, fmt.Errorf("unmarshal cached response: %w", err)
					}
				}
				return gen.CreateEntity201JSONResponse{
					Body:    entity,
					Headers: gen.CreateEntity201ResponseHeaders{ETag: `"` + strconv.Itoa(entity.Version) + `"`},
				}, nil
			}
			// Forward cached error response.
			return gen.CreateEntitydefaultApplicationProblemPlusJSONResponse{
				Body:       gen.Problem{Status: int(*cached.ResponseCode), Title: "replayed error"},
				StatusCode: int(*cached.ResponseCode),
			}, nil
		}
	}

	id := uuid.New()
	slug := req.Body.Slug
	if slug == "" {
		slug = req.Body.Type + ":" + req.Body.Name
	}

	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)
	q := sqlcgen.New(tx)

	// Validate type exists and is NOT abstract.
	var isAbstract bool
	if err := tx.QueryRow(ctx, `SELECT is_abstract FROM entity_types WHERE name = $1`, req.Body.Type).Scan(&isAbstract); err != nil {
		if err == pgx.ErrNoRows {
			return nil, fmt.Errorf("%w: entity type %q", domain.ErrNotFound, req.Body.Type)
		}
		return nil, err
	}
	if isAbstract {
		return nil, fmt.Errorf("%w: %s", domain.ErrAbstractType, req.Body.Type)
	}

	// Get default state from lifecycle.
	var defaultState *string
	var lcDefault string
	if err := tx.QueryRow(ctx, `SELECT ld.default_state FROM lifecycle_defs ld
		JOIN entity_types et ON et.lifecycle_id = ld.id
		WHERE et.name = $1`, req.Body.Type).Scan(&lcDefault); err == nil {
		defaultState = &lcDefault
	}

	state := req.Body.State
	if state == nil && defaultState != nil {
		state = defaultState
	}

	var attrsJSON []byte
	if req.Body.Attributes != nil {
		attrsJSON, _ = json.Marshal(req.Body.Attributes)
	}

	// Insert the entity.
	inserted, err := q.InsertEntity(ctx, sqlcgen.InsertEntityParams{
		ID:         id,
		Slug:       slug,
		Type:       req.Body.Type,
		Name:       req.Body.Name,
		State:      state,
		Attributes: attrsJSON,
	})
	if err != nil {
		// Duplicate slug.
		if strings.Contains(err.Error(), "unique") || strings.Contains(err.Error(), "duplicate") {
			return nil, fmt.Errorf("%w: slug %q already exists", domain.ErrAlreadyExists, slug)
		}
		return nil, err
	}

	// Convert sqlcgen.Entity → gen.Entity.
	entity := sqlcEntityToGen(inserted)

	// Cache idempotent response.
	if req.Params.IdempotencyKey != nil && *req.Params.IdempotencyKey != "" {
		respBody, _ := json.Marshal(entity)
		code := int32(201)
		if bodyHash == "" {
			bodyJSON, _ := json.Marshal(req.Body)
			bodyHash = fmt.Sprintf("%x", sha256.Sum256(bodyJSON))
		}
		if putErr := q.PutIdempotentResponse(ctx, sqlcgen.PutIdempotentResponseParams{
			Actor:        actor,
			Key:          *req.Params.IdempotencyKey,
			RequestHash:  bodyHash,
			ResponseCode: &code,
			ResponseBody: respBody,
		}); putErr != nil {
			return nil, putErr
		}
	}

	// Audit.
	entityID := inserted.ID
	if auditErr := observability.Audit(ctx, q, "operator", actor, "create",
		&entityID, "POST", "/api/v1/entities", "",
		map[string]any{"type": req.Body.Type, "slug": slug}); auditErr != nil {
		return nil, auditErr
	}

	if eventErr := observability.Event(ctx, q, "entity.created", &entityID,
		"info", "oikos-api", "",
		map[string]any{"slug": slug, "type": req.Body.Type}); eventErr != nil {
		return nil, eventErr
	}

	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}

	return gen.CreateEntity201JSONResponse{
		Body:    entity,
		Headers: gen.CreateEntity201ResponseHeaders{ETag: `"` + strconv.Itoa(entity.Version) + `"`},
	}, nil
}

func (s *Server) PatchEntity(ctx context.Context, req gen.PatchEntityRequestObject) (gen.PatchEntityResponseObject, error) {
	if req.Body == nil {
		return nil, fmt.Errorf("%w: request body is required", domain.ErrInvalidInput)
	}

	id, err := s.resolveEntityID(ctx, req.Id)
	if err != nil {
		return nil, err
	}

	// Parse If-Match header (quoted version string).
	ifMatch := strings.Trim(req.Params.IfMatch, `"`)
	expectedVersion, err := strconv.Atoi(ifMatch)
	if err != nil {
		return nil, fmt.Errorf("%w: invalid If-Match header %q", domain.ErrInvalidInput, req.Params.IfMatch)
	}

	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)

	// Get current entity for version check + lifecycle validation.
	current, err := sqlcgen.New(tx).GetEntityByID(ctx, id)
	if err != nil {
		if err == pgx.ErrNoRows {
			return nil, fmt.Errorf("%w: %s", domain.ErrNotFound, req.Id)
		}
		return nil, err
	}

	if int(current.Version) != expectedVersion {
		return nil, fmt.Errorf("%w: expected version %d, current version %d",
			domain.ErrConflict, expectedVersion, current.Version)
	}

	// Validate lifecycle transition if state is being changed.
	if req.Body.State != nil && *req.Body.State != "" {
		// Get lifecycle def for the entity's type.
		lc, err := sqlcgen.New(tx).GetLifecycleForType(ctx, current.Type)
		if err != nil {
			if err == pgx.ErrNoRows {
				// No lifecycle defined — any state is allowed.
				_ = lc
			} else {
				return nil, err
			}
		} else {
			// Check the transition is valid.
			var transitions map[string][]string
			if err := json.Unmarshal(lc.Transitions, &transitions); err != nil {
				return nil, fmt.Errorf("parse lifecycle transitions: %w", err)
			}

			fromState := ""
			if current.State != nil {
				fromState = *current.State
			}
			toState := *req.Body.State

			if allowed, ok := transitions[fromState]; ok {
				found := false
				for _, s := range allowed {
					if s == toState {
						found = true
						break
					}
				}
				if !found {
					return nil, fmt.Errorf("%w: %s → %s", domain.ErrInvalidTransition, fromState, toState)
				}
			} else if fromState != "" {
				// No transitions defined from current state.
				return nil, fmt.Errorf("%w: %s → %s", domain.ErrInvalidTransition, fromState, toState)
			}
		}
	}

	// Check idempotency (note: the spec doesn't define Idempotency-Key for PATCH,
	// but we handle it if the generated code ever adds it).
	// For now, no idempotency check on PATCH.

	// Marshal attributes if provided.
	var attrsJSON []byte
	if req.Body.Attributes != nil {
		attrsJSON, _ = json.Marshal(req.Body.Attributes)
	}

	// Perform the update via sqlcgen.
	q := sqlcgen.New(tx)
	updated, err := q.UpdateEntity(ctx, sqlcgen.UpdateEntityParams{
		Name:             req.Body.Name,
		State:            req.Body.State,
		Attributes:       attrsJSON,
		SetMaintenance:   req.Body.MaintenanceUntil != nil,
		MaintenanceUntil: req.Body.MaintenanceUntil,
		ID:               id,
		Version:          int32(expectedVersion),
	})
	if err != nil {
		if err == pgx.ErrNoRows {
			// Version mismatch or entity not found.
			return nil, fmt.Errorf("%w: entity was modified concurrently", domain.ErrConflict)
		}
		return nil, err
	}

	entity := sqlcEntityToGen(updated)

	// Audit.
	if auditErr := observability.Audit(ctx, q, "operator", "operator", "patch",
		&id, "PATCH", "/api/v1/entities/"+req.Id, "",
		map[string]any{"version": expectedVersion}); auditErr != nil {
		return nil, auditErr
	}

	if eventErr := observability.Event(ctx, q, "entity.updated", &id,
		"info", "oikos-api", "",
		map[string]any{"slug": entity.Slug, "type": entity.Type, "version": updated.Version}); eventErr != nil {
		return nil, eventErr
	}

	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}

	return gen.PatchEntity200JSONResponse{
		Body:    entity,
		Headers: gen.PatchEntity200ResponseHeaders{ETag: `"` + strconv.Itoa(entity.Version) + `"`},
	}, nil
}

// sqlcEntityToGen converts a sqlcgen.Entity to a gen.Entity.
func sqlcEntityToGen(e sqlcgen.Entity) gen.Entity {
	out := gen.Entity{
		Id:        e.ID,
		Slug:      e.Slug,
		Type:      e.Type,
		Name:      e.Name,
		State:     e.State,
		Version:   int(e.Version),
		CreatedAt: e.CreatedAt,
		UpdatedAt: e.UpdatedAt,
	}
	if e.MaintenanceUntil != nil {
		out.MaintenanceUntil = e.MaintenanceUntil
	}
	if len(e.Attributes) > 0 {
		var attrs map[string]any
		if json.Unmarshal(e.Attributes, &attrs) == nil && len(attrs) > 0 {
			out.Attributes = &attrs
		}
	}
	return out
}