package db

import (
	"database/sql"
	"errors"
	"fmt"
	"strings"
)

// Sentinel errors callers can match against. The server layer maps these
// to HTTP status codes.
var (
	ErrNotFound      = errors.New("not found")
	ErrConflict      = errors.New("conflict")            // UNIQUE violation
	ErrInUse         = errors.New("in use")              // cable_type referenced by a cable
	ErrConfirmName   = errors.New("confirm name missing or mismatched")
	ErrInvalidInput  = errors.New("invalid input")
)

// -----------------------------------------------------------------------------
// Projects
// -----------------------------------------------------------------------------

// CreateProject inserts a new project. drawingName, if empty, defaults to
// "<name>.excalidraw". name and drawingName are trimmed; an empty name
// after trimming is rejected.
func (s *Store) CreateProject(name, drawingName, description string) (*Project, error) {
	name = strings.TrimSpace(name)
	drawingName = strings.TrimSpace(drawingName)
	if name == "" {
		return nil, fmt.Errorf("%w: name is required", ErrInvalidInput)
	}
	if drawingName == "" {
		drawingName = name + ".excalidraw"
	}

	res, err := s.db.Exec(
		`INSERT INTO projects (name, drawing_name, description) VALUES (?, ?, ?)`,
		name, drawingName, description,
	)
	if err != nil {
		return nil, mapWriteErr(err)
	}
	id, _ := res.LastInsertId()
	return s.GetProject(id)
}

// GetProject loads a project by ID.
func (s *Store) GetProject(id int64) (*Project, error) {
	var p Project
	err := s.db.QueryRow(
		`SELECT id, name, drawing_name, description, created_at, updated_at
		 FROM projects WHERE id = ?`, id,
	).Scan(&p.ID, &p.Name, &p.DrawingName, &p.Description, &p.CreatedAt, &p.UpdatedAt)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &p, nil
}

// ListProjects returns every project ordered by name.
func (s *Store) ListProjects() ([]Project, error) {
	rows, err := s.db.Query(
		`SELECT id, name, drawing_name, description, created_at, updated_at
		 FROM projects ORDER BY name`,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []Project
	for rows.Next() {
		var p Project
		if err := rows.Scan(&p.ID, &p.Name, &p.DrawingName, &p.Description, &p.CreatedAt, &p.UpdatedAt); err != nil {
			return nil, err
		}
		out = append(out, p)
	}
	return out, rows.Err()
}

// ProjectUpdate carries partial fields for PATCH. A nil pointer means
// "leave this field untouched".
type ProjectUpdate struct {
	Name        *string
	DrawingName *string
	Description *string
}

// UpdateProject applies the partial update. Empty struct = no-op (just
// bumps updated_at). Empty Name (after trim) is rejected; whitespace-only
// DrawingName is treated as "use <name>.excalidraw" — same default as
// CreateProject.
func (s *Store) UpdateProject(id int64, u ProjectUpdate) (*Project, error) {
	cur, err := s.GetProject(id)
	if err != nil {
		return nil, err
	}

	if u.Name != nil {
		v := strings.TrimSpace(*u.Name)
		if v == "" {
			return nil, fmt.Errorf("%w: name cannot be empty", ErrInvalidInput)
		}
		cur.Name = v
	}
	if u.DrawingName != nil {
		v := strings.TrimSpace(*u.DrawingName)
		if v == "" {
			v = cur.Name + ".excalidraw"
		}
		cur.DrawingName = v
	}
	if u.Description != nil {
		cur.Description = *u.Description
	}

	if _, err := s.db.Exec(
		`UPDATE projects
		 SET name = ?, drawing_name = ?, description = ?, updated_at = datetime('now')
		 WHERE id = ?`,
		cur.Name, cur.DrawingName, cur.Description, id,
	); err != nil {
		return nil, mapWriteErr(err)
	}
	return s.GetProject(id)
}

// DeleteProject removes the project (cascading frames, devices, ports,
// cables, io_markers, bundles, bundle_cables). confirmName must match the
// project's current name; otherwise ErrConfirmName is returned and nothing
// is deleted.
func (s *Store) DeleteProject(id int64, confirmName string) error {
	p, err := s.GetProject(id)
	if err != nil {
		return err
	}
	if confirmName != p.Name {
		return ErrConfirmName
	}
	if _, err := s.db.Exec(`DELETE FROM projects WHERE id = ?`, id); err != nil {
		return err
	}
	return nil
}

// Snapshot loads the full editor-init payload for one project. Slice 2
// populates frames + devices; ports / cables / io_markers / bundles
// still ship empty until their slices land.
func (s *Store) Snapshot(id int64) (*Snapshot, error) {
	p, err := s.GetProject(id)
	if err != nil {
		return nil, err
	}
	types, err := s.ListCableTypes()
	if err != nil {
		return nil, err
	}
	frames, err := s.ListFrames(id)
	if err != nil {
		return nil, err
	}
	devices, err := s.ListDevices(id, nil)
	if err != nil {
		return nil, err
	}
	ios, err := s.ListIOMarkers(id)
	if err != nil {
		return nil, err
	}
	ports, err := s.ListPortsForProject(id)
	if err != nil {
		return nil, err
	}
	reqs, err := s.ListConnectionRequirements(id)
	if err != nil {
		return nil, err
	}
	cables, err := s.ListCables(id)
	if err != nil {
		return nil, err
	}
	bundles, err := s.ListBundles(id)
	if err != nil {
		return nil, err
	}
	clamps, err := s.ListClamps(id)
	if err != nil {
		return nil, err
	}
	cableClamps, err := s.ListCableClamps(id)
	if err != nil {
		return nil, err
	}
	return &Snapshot{
		Project:                *p,
		Frames:                 frames,
		Devices:                devices,
		Ports:                  ports,
		Cables:                 cables,
		IOMarkers:              ios,
		Bundles:                bundles,
		CableTypes:             types,
		ConnectionRequirements: reqs,
		Clamps:                 clamps,
		CableClamps:            cableClamps,
	}, nil
}

// -----------------------------------------------------------------------------
// Cable types (global)
// -----------------------------------------------------------------------------

// CreateCableType inserts a global cable type. name must be globally unique.
func (s *Store) CreateCableType(name, color string) (*CableType, error) {
	name = strings.TrimSpace(name)
	color = strings.TrimSpace(color)
	if name == "" {
		return nil, fmt.Errorf("%w: name is required", ErrInvalidInput)
	}
	if color == "" {
		return nil, fmt.Errorf("%w: color is required", ErrInvalidInput)
	}
	res, err := s.db.Exec(
		`INSERT INTO cable_types (name, color) VALUES (?, ?)`, name, color,
	)
	if err != nil {
		return nil, mapWriteErr(err)
	}
	id, _ := res.LastInsertId()
	return s.GetCableType(id)
}

// GetCableType loads a cable type by ID.
func (s *Store) GetCableType(id int64) (*CableType, error) {
	var t CableType
	err := s.db.QueryRow(
		`SELECT id, name, color, created_at, updated_at
		 FROM cable_types WHERE id = ?`, id,
	).Scan(&t.ID, &t.Name, &t.Color, &t.CreatedAt, &t.UpdatedAt)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &t, nil
}

// ListCableTypes returns every cable type ordered by id (insertion order,
// so the legend renders in the same order across reloads).
func (s *Store) ListCableTypes() ([]CableType, error) {
	rows, err := s.db.Query(
		`SELECT id, name, color, created_at, updated_at
		 FROM cable_types ORDER BY id`,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []CableType{}
	for rows.Next() {
		var t CableType
		if err := rows.Scan(&t.ID, &t.Name, &t.Color, &t.CreatedAt, &t.UpdatedAt); err != nil {
			return nil, err
		}
		out = append(out, t)
	}
	return out, rows.Err()
}

// CableTypeUpdate is the partial-update shape for PATCH.
type CableTypeUpdate struct {
	Name  *string
	Color *string
}

// UpdateCableType applies a partial update.
func (s *Store) UpdateCableType(id int64, u CableTypeUpdate) (*CableType, error) {
	cur, err := s.GetCableType(id)
	if err != nil {
		return nil, err
	}
	if u.Name != nil {
		v := strings.TrimSpace(*u.Name)
		if v == "" {
			return nil, fmt.Errorf("%w: name cannot be empty", ErrInvalidInput)
		}
		cur.Name = v
	}
	if u.Color != nil {
		v := strings.TrimSpace(*u.Color)
		if v == "" {
			return nil, fmt.Errorf("%w: color cannot be empty", ErrInvalidInput)
		}
		cur.Color = v
	}
	if _, err := s.db.Exec(
		`UPDATE cable_types
		 SET name = ?, color = ?, updated_at = datetime('now')
		 WHERE id = ?`,
		cur.Name, cur.Color, id,
	); err != nil {
		return nil, mapWriteErr(err)
	}
	return s.GetCableType(id)
}

// DeleteCableType removes a cable type. SQLite enforces ON DELETE RESTRICT
// from cables.type_id and ports.type_id; we surface that as ErrInUse plus
// the count of referencing cables (so the UI can show "blocked by N cables").
func (s *Store) DeleteCableType(id int64) error {
	if _, err := s.GetCableType(id); err != nil {
		return err
	}
	if _, err := s.db.Exec(`DELETE FROM cable_types WHERE id = ?`, id); err != nil {
		if isForeignKeyConstraint(err) {
			return ErrInUse
		}
		return err
	}
	return nil
}

// CountCablesUsingType returns how many cables reference this cable_type.
// Used by the server to enrich a 409 InUse response with a helpful number.
func (s *Store) CountCablesUsingType(id int64) (int, error) {
	var n int
	err := s.db.QueryRow(`SELECT COUNT(*) FROM cables WHERE type_id = ?`, id).Scan(&n)
	return n, err
}

// -----------------------------------------------------------------------------
// Error mapping
// -----------------------------------------------------------------------------

// mapWriteErr classifies SQLite write errors into our sentinel errors so
// the handler layer can pick the right HTTP status. Falls through to the
// raw error for anything we don't recognise.
func mapWriteErr(err error) error {
	if err == nil {
		return nil
	}
	msg := err.Error()
	switch {
	case strings.Contains(msg, "UNIQUE constraint failed"):
		return fmt.Errorf("%w: %s", ErrConflict, msg)
	case strings.Contains(msg, "FOREIGN KEY constraint failed"):
		return fmt.Errorf("%w: %s", ErrInUse, msg)
	case strings.Contains(msg, "CHECK constraint failed"):
		return fmt.Errorf("%w: %s", ErrInvalidInput, msg)
	}
	return err
}

func isForeignKeyConstraint(err error) bool {
	return err != nil && strings.Contains(err.Error(), "FOREIGN KEY constraint failed")
}