package db

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

// ConnectionRequirementCreate is the create-shape. Server normalises
// from/to into (pair_lo, pair_hi) so (A,B,T) and (B,A,T) collide.
type ConnectionRequirementCreate struct {
	FromDeviceID         int64
	ToDeviceID           int64
	PreferredCableTypeID *int64
	MustConnect          *bool // pointer so "absent" defaults to true
	Notes                string
}

// ConnectionRequirementUpdate is the partial-update shape. project_id +
// the device pair are immutable post-create (changing either is best
// modelled as delete-then-create — keeps pair_lo/pair_hi semantics simple).
type ConnectionRequirementUpdate struct {
	PreferredCableTypeID FrameRef // tri-state: leave / set / clear
	MustConnect          *bool
	Notes                *string
}

// CreateConnectionRequirement inserts a new requirement. Validates that
// both devices live in projectID, that from != to, and that the
// (project, pair_lo, pair_hi, preferred_cable_type_id) tuple is unique.
func (s *Store) CreateConnectionRequirement(projectID int64, r ConnectionRequirementCreate) (*ConnectionRequirement, error) {
	if r.FromDeviceID == r.ToDeviceID {
		return nil, fmt.Errorf("%w: from_device_id and to_device_id must differ", ErrInvalidInput)
	}
	if _, err := s.GetProject(projectID); err != nil {
		return nil, err
	}
	if _, err := s.GetDevice(projectID, r.FromDeviceID); err != nil {
		if errors.Is(err, ErrNotFound) {
			return nil, fmt.Errorf("%w: from_device_id %d not in project %d", ErrInvalidInput, r.FromDeviceID, projectID)
		}
		return nil, err
	}
	if _, err := s.GetDevice(projectID, r.ToDeviceID); err != nil {
		if errors.Is(err, ErrNotFound) {
			return nil, fmt.Errorf("%w: to_device_id %d not in project %d", ErrInvalidInput, r.ToDeviceID, projectID)
		}
		return nil, err
	}
	if r.PreferredCableTypeID != nil {
		if _, err := s.GetCableType(*r.PreferredCableTypeID); err != nil {
			if errors.Is(err, ErrNotFound) {
				return nil, fmt.Errorf("%w: preferred_cable_type_id %d not found", ErrInvalidInput, *r.PreferredCableTypeID)
			}
			return nil, err
		}
	}
	must := true
	if r.MustConnect != nil {
		must = *r.MustConnect
	}
	mustInt := 0
	if must {
		mustInt = 1
	}
	lo, hi := r.FromDeviceID, r.ToDeviceID
	if lo > hi {
		lo, hi = hi, lo
	}
	res, err := s.db.Exec(
		`INSERT INTO connection_requirements
		   (project_id, from_device_id, to_device_id, preferred_cable_type_id,
		    must_connect, notes, pair_lo, pair_hi)
		 VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
		projectID, r.FromDeviceID, r.ToDeviceID, nullableInt64(r.PreferredCableTypeID),
		mustInt, r.Notes, lo, hi,
	)
	if err != nil {
		return nil, mapWriteErr(err)
	}
	id, _ := res.LastInsertId()
	return s.GetConnectionRequirement(projectID, id)
}

// GetConnectionRequirement loads one by id, project-scoped.
func (s *Store) GetConnectionRequirement(projectID, id int64) (*ConnectionRequirement, error) {
	var r ConnectionRequirement
	var ct sql.NullInt64
	var must int
	err := s.db.QueryRow(
		`SELECT id, project_id, from_device_id, to_device_id, preferred_cable_type_id,
		        must_connect, notes, created_at, updated_at
		 FROM connection_requirements WHERE id = ? AND project_id = ?`, id, projectID,
	).Scan(&r.ID, &r.ProjectID, &r.FromDeviceID, &r.ToDeviceID, &ct,
		&must, &r.Notes, &r.CreatedAt, &r.UpdatedAt)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	if ct.Valid {
		v := ct.Int64
		r.PreferredCableTypeID = &v
	}
	r.MustConnect = must != 0
	return &r, nil
}

// ListConnectionRequirements returns every requirement in a project,
// ordered by id (insertion order).
func (s *Store) ListConnectionRequirements(projectID int64) ([]ConnectionRequirement, error) {
	rows, err := s.db.Query(
		`SELECT id, project_id, from_device_id, to_device_id, preferred_cable_type_id,
		        must_connect, notes, created_at, updated_at
		 FROM connection_requirements WHERE project_id = ? ORDER BY id`, projectID,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []ConnectionRequirement{}
	for rows.Next() {
		var r ConnectionRequirement
		var ct sql.NullInt64
		var must int
		if err := rows.Scan(&r.ID, &r.ProjectID, &r.FromDeviceID, &r.ToDeviceID, &ct,
			&must, &r.Notes, &r.CreatedAt, &r.UpdatedAt); err != nil {
			return nil, err
		}
		if ct.Valid {
			v := ct.Int64
			r.PreferredCableTypeID = &v
		}
		r.MustConnect = must != 0
		out = append(out, r)
	}
	return out, rows.Err()
}

// UpdateConnectionRequirement applies a partial update. preferred_cable_type_id
// uses the FrameRef tri-state; must_connect + notes are plain pointers.
// The (from, to) pair is immutable on PATCH — delete + recreate to change.
func (s *Store) UpdateConnectionRequirement(projectID, id int64, u ConnectionRequirementUpdate) (*ConnectionRequirement, error) {
	cur, err := s.GetConnectionRequirement(projectID, id)
	if err != nil {
		return nil, err
	}
	if u.PreferredCableTypeID.Set {
		if u.PreferredCableTypeID.ID != nil {
			if _, err := s.GetCableType(*u.PreferredCableTypeID.ID); err != nil {
				if errors.Is(err, ErrNotFound) {
					return nil, fmt.Errorf("%w: preferred_cable_type_id %d not found", ErrInvalidInput, *u.PreferredCableTypeID.ID)
				}
				return nil, err
			}
		}
		cur.PreferredCableTypeID = u.PreferredCableTypeID.ID
	}
	if u.MustConnect != nil {
		cur.MustConnect = *u.MustConnect
	}
	if u.Notes != nil {
		cur.Notes = *u.Notes
	}
	mustInt := 0
	if cur.MustConnect {
		mustInt = 1
	}
	if _, err := s.db.Exec(
		`UPDATE connection_requirements
		 SET preferred_cable_type_id = ?, must_connect = ?, notes = ?, updated_at = datetime('now')
		 WHERE id = ? AND project_id = ?`,
		nullableInt64(cur.PreferredCableTypeID), mustInt, cur.Notes, id, projectID,
	); err != nil {
		return nil, mapWriteErr(err)
	}
	return s.GetConnectionRequirement(projectID, id)
}

// DeleteConnectionRequirement removes a requirement by id, project-scoped.
func (s *Store) DeleteConnectionRequirement(projectID, id int64) error {
	if _, err := s.GetConnectionRequirement(projectID, id); err != nil {
		return err
	}
	if _, err := s.db.Exec(
		`DELETE FROM connection_requirements WHERE id = ? AND project_id = ?`, id, projectID,
	); err != nil {
		return err
	}
	return nil
}