package fn_operations

import (
	"fmt"
	"time"

	"fn-registry/registry"
)

// InsertEntityWithSnapshot inserts an entity, snapshotting its type from the registry if needed.
// registryDB can be nil if the type is already snapshotted.
func InsertEntityWithSnapshot(opsDB *DB, registryDB *registry.DB, e *Entity) error {
	if err := ValidateEntity(e); err != nil {
		return err
	}

	// Check if type is already snapshotted
	snap, err := opsDB.GetTypeSnapshot(e.TypeRef)
	if err != nil {
		return fmt.Errorf("checking type snapshot: %w", err)
	}

	if snap == nil {
		// Need to fetch from registry
		if registryDB == nil {
			return fmt.Errorf("type %q not found in local snapshots and no registry provided", e.TypeRef)
		}
		if err := SnapshotType(opsDB, registryDB, e.TypeRef); err != nil {
			return err
		}
	}

	return opsDB.InsertEntity(e)
}

// SnapshotType fetches a type from the registry and copies it to types_snapshot.
func SnapshotType(opsDB *DB, registryDB *registry.DB, typeID string) error {
	t, err := registryDB.GetType(typeID)
	if err != nil {
		return fmt.Errorf("fetching type %q from registry: %w", typeID, err)
	}

	snap := &TypeSnapshot{
		ID:          t.ID,
		Version:     t.Version,
		Lang:        t.Lang,
		Algebraic:   string(t.Algebraic),
		Definition:  t.Definition,
		Description: t.Description,
		SnappedAt:   time.Now().UTC(),
	}

	return opsDB.InsertTypeSnapshot(snap)
}

// InsertRelationSafe validates, checks for cycles, and inserts a relation.
func InsertRelationSafe(db *DB, r *Relation) error {
	entities, err := buildEntitySet(db)
	if err != nil {
		return err
	}

	if err := ValidateRelation(r, entities); err != nil {
		return err
	}

	// from_entity is required when not using relation_inputs
	if r.FromEntity == "" {
		return fmt.Errorf("from_entity is required (use InsertRelationWithInputs for multi-input relations)")
	}

	// Cycle detection only for causal relations
	if r.Via != "" {
		if err := DetectCycle(db, r.FromEntity, r.ToEntity); err != nil {
			return err
		}
	}

	return db.InsertRelation(r)
}

// InsertRelationWithInputs validates and inserts a relation with multiple inputs in a transaction.
func InsertRelationWithInputs(db *DB, r *Relation, inputs []RelationInput) error {
	entities, err := buildEntitySet(db)
	if err != nil {
		return err
	}

	if err := ValidateRelation(r, entities); err != nil {
		return err
	}
	if err := ValidateRelationInputs(inputs, entities); err != nil {
		return err
	}

	// Cycle detection for each input if causal
	if r.Via != "" {
		for _, input := range inputs {
			if err := DetectCycle(db, input.EntityID, r.ToEntity); err != nil {
				return err
			}
		}
	}

	tx, err := db.Conn().Begin()
	if err != nil {
		return fmt.Errorf("beginning transaction: %w", err)
	}
	defer tx.Rollback()

	// Insert relation
	now := time.Now().UTC()
	if r.CreatedAt.IsZero() {
		r.CreatedAt = now
	}
	r.UpdatedAt = now

	var startedAt, endedAt *string
	if r.StartedAt != nil {
		s := r.StartedAt.Format(time.RFC3339)
		startedAt = &s
	}
	if r.EndedAt != nil {
		s := r.EndedAt.Format(time.RFC3339)
		endedAt = &s
	}

	_, err = tx.Exec(`
		INSERT OR REPLACE INTO relations (id, name, from_entity, to_entity, via, description, purity, direction, weight, status, started_at, ended_at, "order", tags, notes, created_at, updated_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		r.ID, r.Name, r.FromEntity, r.ToEntity, r.Via, r.Description,
		r.Purity, string(r.Direction), r.Weight, string(r.Status),
		startedAt, endedAt, r.Order, marshalStrings(r.Tags), r.Notes,
		r.CreatedAt.Format(time.RFC3339), r.UpdatedAt.Format(time.RFC3339),
	)
	if err != nil {
		return fmt.Errorf("inserting relation: %w", err)
	}

	// Insert inputs
	for _, ri := range inputs {
		_, err = tx.Exec(`
			INSERT INTO relation_inputs (id, relation_id, entity_id, role, "order")
			VALUES (?, ?, ?, ?, ?)`,
			ri.ID, ri.RelationID, ri.EntityID, ri.Role, ri.Order,
		)
		if err != nil {
			return fmt.Errorf("inserting relation_input: %w", err)
		}
	}

	return tx.Commit()
}

// Graph holds the full entity-relation graph for a project.
type Graph struct {
	Entities  []Entity
	Relations []Relation
	Inputs    map[string][]RelationInput
}

// GetEntityGraph returns all entities and relations for visualization.
func GetEntityGraph(db *DB) (*Graph, error) {
	entities, err := db.ListEntities("", "")
	if err != nil {
		return nil, fmt.Errorf("listing entities: %w", err)
	}

	relations, err := db.ListRelations("")
	if err != nil {
		return nil, fmt.Errorf("listing relations: %w", err)
	}

	inputs := map[string][]RelationInput{}
	for _, r := range relations {
		ri, err := db.GetRelationInputs(r.ID)
		if err != nil {
			return nil, fmt.Errorf("getting inputs for relation %s: %w", r.ID, err)
		}
		if len(ri) > 0 {
			inputs[r.ID] = ri
		}
	}

	return &Graph{
		Entities:  entities,
		Relations: relations,
		Inputs:    inputs,
	}, nil
}

func buildEntitySet(db *DB) (map[string]bool, error) {
	all, err := db.ListEntities("", "")
	if err != nil {
		return nil, fmt.Errorf("building entity set: %w", err)
	}
	set := make(map[string]bool, len(all))
	for _, e := range all {
		set[e.ID] = true
	}
	return set, nil
}