package services

// ProjectService handles CRUD on paliad.projects — the hierarchical
// project tree that replaced the flat paliad.akten model in migration 018.
//
// Visibility (design v2, adjusted 2026-04-20): team-based only.
//   A user can see a Project iff
//     - user is admin, or
//     - user is a direct member of the Project's team, or
//     - user is a member of any ancestor Project's team (inherited via path).
//
// Office is no longer a visibility gate. Cases associate with lead partners,
// not offices (see paliad.project_teams role='lead').
//
// The canonical predicate lives in SQL (paliad.can_see_project) and is
// enforced by RLS policies. This service re-implements the same predicate
// at the application layer so the service-role DB connection (without an
// auth.uid() JWT) still gates correctly.

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/google/uuid"
	"github.com/jmoiron/sqlx"
	"github.com/lib/pq"

	"mgit.msbls.de/m/patholo/internal/models"
)

// Sentinel errors.
var (
	// ErrNotVisible indicates the Project exists but the user has no
	// visibility. Handlers must map to 404 (never leak existence).
	ErrNotVisible = errors.New("project not visible")
	// ErrForbidden indicates the user is authenticated but lacks the role
	// required for the operation (e.g., associate trying to delete).
	ErrForbidden = errors.New("forbidden")
	// ErrInvalidInput signals a bad request (empty required field etc.).
	ErrInvalidInput = errors.New("invalid input")
)

// ProjectType values enumerated on the projects.type CHECK constraint.
const (
	ProjectTypeClient     = "client"
	ProjectTypeLitigation = "litigation"
	ProjectTypePatent     = "patent"
	ProjectTypeCase       = "case"
	ProjectTypeProject    = "project"
)

// ProjektRole values allowed on project_teams.role.
const (
	RoleLead         = "lead"
	RoleAssociate    = "associate"
	RolePA           = "pa"
	RoleOfCounsel    = "of_counsel"
	RoleLocalCounsel = "local_counsel"
	RoleExpert       = "expert"
	RoleObserver     = "observer"
)

// ProjectService reads and writes paliad.projects + paliad.project_events.
type ProjectService struct {
	db    *sqlx.DB
	users *UserService
}

// NewProjectService wires the service.
func NewProjectService(db *sqlx.DB, users *UserService) *ProjectService {
	return &ProjectService{db: db, users: users}
}

// Users exposes the shared user service for downstream services that gate
// through ProjectService (DeadlineService, AppointmentService, NoteService, …).
func (s *ProjectService) Users() *UserService { return s.users }

// DB exposes the underlying connection pool for services that need to issue
// custom queries (dashboard aggregates, caldav sync). Read-only usage.
func (s *ProjectService) DB() *sqlx.DB { return s.db }

const projektColumns = `id, type, parent_id, path, title, reference, description, status,
	created_by, industry, country, billing_reference, client_number, matter_number,
	netdocuments_url, patent_number, filing_date, grant_date, court, case_number,
	proceeding_type_id, metadata, ai_summary, created_at, updated_at`

// CreateProjektInput is the payload for Create.
type CreateProjektInput struct {
	Type        string     `json:"type"`
	ParentID    *uuid.UUID `json:"parent_id,omitempty"`
	Title       string     `json:"title"`
	Reference   *string    `json:"reference,omitempty"`
	Description *string    `json:"description,omitempty"`
	Status      string     `json:"status,omitempty"` // default "active"

	// Type-specific; service applies only the subset matching Type.
	Industry         *string    `json:"industry,omitempty"`
	Country          *string    `json:"country,omitempty"`
	BillingReference *string    `json:"billing_reference,omitempty"`
	ClientNumber     *string    `json:"client_number,omitempty"`
	MatterNumber     *string    `json:"matter_number,omitempty"`
	NetDocumentsURL  *string    `json:"netdocuments_url,omitempty"`
	PatentNumber     *string    `json:"patent_number,omitempty"`
	FilingDate       *time.Time `json:"filing_date,omitempty"`
	GrantDate        *time.Time `json:"grant_date,omitempty"`
	Court            *string    `json:"court,omitempty"`
	CaseNumber       *string    `json:"case_number,omitempty"`
	ProceedingTypeID *int       `json:"proceeding_type_id,omitempty"`
}

// UpdateProjektInput is the partial-update payload.
type UpdateProjektInput struct {
	Type        *string `json:"type,omitempty"`
	Title       *string `json:"title,omitempty"`
	Reference   *string `json:"reference,omitempty"`
	Description *string `json:"description,omitempty"`
	Status      *string `json:"status,omitempty"`
	ParentID    *uuid.UUID `json:"parent_id,omitempty"` // reparent; server recomputes path

	Industry         *string    `json:"industry,omitempty"`
	Country          *string    `json:"country,omitempty"`
	BillingReference *string    `json:"billing_reference,omitempty"`
	ClientNumber     *string    `json:"client_number,omitempty"`
	MatterNumber     *string    `json:"matter_number,omitempty"`
	NetDocumentsURL  *string    `json:"netdocuments_url,omitempty"`
	PatentNumber     *string    `json:"patent_number,omitempty"`
	FilingDate       *time.Time `json:"filing_date,omitempty"`
	GrantDate        *time.Time `json:"grant_date,omitempty"`
	Court            *string    `json:"court,omitempty"`
	CaseNumber       *string    `json:"case_number,omitempty"`
	ProceedingTypeID *int       `json:"proceeding_type_id,omitempty"`
}

// ListFilter narrows List results. Zero-value → no filter.
type ProjectFilter struct {
	Type     string     // "", or one of ProjectType* constants
	Status   string     // "", "active", "archived", "closed"
	ParentID *uuid.UUID // filter to direct children of the given parent; use ParentNullOnly for roots
	// ParentNullOnly restricts to root-level rows (parent_id IS NULL).
	// Mutually exclusive with ParentID.
	ParentNullOnly bool
	Search         string // trigram / ILIKE on title, reference, client_number, matter_number
}

// List returns Projects visible to the user, filterable.
func (s *ProjectService) List(ctx context.Context, userID uuid.UUID, f ProjectFilter) ([]models.Project, error) {
	user, err := s.users.GetByID(ctx, userID)
	if err != nil {
		return nil, err
	}
	if user == nil {
		return []models.Project{}, nil
	}

	conds := []string{visibilityPredicate("p")}
	args := map[string]any{
		"user_id": userID,
	}

	if f.Type != "" {
		conds = append(conds, "p.type = :type")
		args["type"] = f.Type
	}
	if f.Status != "" {
		conds = append(conds, "p.status = :status")
		args["status"] = f.Status
	}
	if f.ParentNullOnly {
		conds = append(conds, "p.parent_id IS NULL")
	} else if f.ParentID != nil {
		conds = append(conds, "p.parent_id = :parent_id")
		args["parent_id"] = *f.ParentID
	}
	if s := strings.TrimSpace(f.Search); s != "" {
		conds = append(conds, `(p.title ILIKE :search OR p.reference ILIKE :search
			OR p.client_number ILIKE :search OR p.matter_number ILIKE :search)`)
		args["search"] = "%" + s + "%"
	}

	query := `SELECT ` + projektColumns + ` FROM paliad.projects p
	           WHERE ` + strings.Join(conds, " AND ") + `
	           ORDER BY p.updated_at DESC`

	stmt, err := s.db.PrepareNamedContext(ctx, query)
	if err != nil {
		return nil, fmt.Errorf("prepare list projects: %w", err)
	}
	defer stmt.Close()

	rows := []models.Project{}
	if err := stmt.SelectContext(ctx, &rows, args); err != nil {
		return nil, fmt.Errorf("list projects: %w", err)
	}
	return rows, nil
}

// GetByID returns the Project if the user can see it. Returns (nil, ErrNotVisible)
// when invisible or missing — handlers must not distinguish.
func (s *ProjectService) GetByID(ctx context.Context, userID, id uuid.UUID) (*models.Project, error) {
	user, err := s.users.GetByID(ctx, userID)
	if err != nil {
		return nil, err
	}
	if user == nil {
		return nil, ErrNotVisible
	}
	var p models.Project
	query := `SELECT ` + projektColumns + ` FROM paliad.projects p
	          WHERE p.id = $1 AND ` + visibilityPredicatePositional("p", 2)
	err = s.db.GetContext(ctx, &p, query, id, userID)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrNotVisible
	}
	if err != nil {
		return nil, fmt.Errorf("get project: %w", err)
	}
	return &p, nil
}

// ListChildren returns direct children of a Project (visibility-checked on parent).
func (s *ProjectService) ListChildren(ctx context.Context, userID, id uuid.UUID) ([]models.Project, error) {
	if _, err := s.GetByID(ctx, userID, id); err != nil {
		return nil, err
	}
	return s.List(ctx, userID, ProjectFilter{ParentID: &id})
}

// ListAncestors walks up the path and returns ancestors from root → parent
// (exclusive of the Project itself). Used for breadcrumbs.
func (s *ProjectService) ListAncestors(ctx context.Context, userID, id uuid.UUID) ([]models.Project, error) {
	p, err := s.GetByID(ctx, userID, id)
	if err != nil {
		return nil, err
	}
	labels := strings.Split(p.Path, ".")
	if len(labels) <= 1 {
		return []models.Project{}, nil
	}
	// All but last = ancestors.
	ancestorIDs := labels[:len(labels)-1]
	ids := make([]uuid.UUID, 0, len(ancestorIDs))
	for _, s := range ancestorIDs {
		u, err := uuid.Parse(s)
		if err != nil {
			return nil, fmt.Errorf("parse ancestor uuid %q: %w", s, err)
		}
		ids = append(ids, u)
	}
	user, err := s.users.GetByID(ctx, userID)
	if err != nil {
		return nil, err
	}
	if user == nil {
		return []models.Project{}, nil
	}
	// Ancestors are visible whenever the Project is (inheritance works both
	// ways through team membership checks). We still apply the predicate
	// for safety in case path is stale.
	query := `SELECT ` + projektColumns + ` FROM paliad.projects p
	          WHERE p.id = ANY($1::uuid[]) AND ` +
		visibilityPredicatePositional("p", 2)
	// lib/pq doesn't serialise []uuid.UUID natively; render as string array.
	idStrs := make([]string, len(ids))
	for i, u := range ids {
		idStrs[i] = u.String()
	}
	rows := []models.Project{}
	if err := s.db.SelectContext(ctx, &rows, query, pq.StringArray(idStrs), userID); err != nil {
		return nil, fmt.Errorf("list ancestors: %w", err)
	}
	// Re-order to match path order (root first).
	order := make(map[uuid.UUID]int, len(ids))
	for i, id := range ids {
		order[id] = i
	}
	sortByOrder(rows, order)
	return rows, nil
}

// ProjectTreeNode is one node of the nested tree returned by BuildTree.
// It embeds the full Project plus aggregated child nodes and deadline
// counts so the UI can render badges without per-row API calls.
type ProjectTreeNode struct {
	models.Project
	Children         []*ProjectTreeNode `json:"children"`
	OpenDeadlines    int                `json:"open_deadlines"`
	OverdueDeadlines int                `json:"overdue_deadlines"`
}

// BuildTree returns the full nested tree of every Project the user can see,
// rooted at all parent_id-IS-NULL projects. Each node carries its open and
// overdue deadline counts (open=pending, overdue=pending&past-due) so the UI
// can render status badges with no extra round-trips. Path-sorted so callers
// get a stable deterministic ordering.
func (s *ProjectService) BuildTree(ctx context.Context, userID uuid.UUID) ([]*ProjectTreeNode, error) {
	user, err := s.users.GetByID(ctx, userID)
	if err != nil {
		return nil, err
	}
	if user == nil {
		return []*ProjectTreeNode{}, nil
	}

	query := `SELECT ` + projektColumns + ` FROM paliad.projects p
	          WHERE ` + visibilityPredicatePositional("p", 1) + `
	          ORDER BY p.path`
	rows := []models.Project{}
	if err := s.db.SelectContext(ctx, &rows, query, userID); err != nil {
		return nil, fmt.Errorf("build tree list: %w", err)
	}

	type deadlineCount struct {
		ProjectID uuid.UUID `db:"project_id"`
		Open      int       `db:"open"`
		Overdue   int       `db:"overdue"`
	}
	now := time.Now().UTC()
	today := now.Truncate(24 * time.Hour)
	var counts []deadlineCount
	if err := s.db.SelectContext(ctx, &counts, `
		SELECT f.project_id,
		       COUNT(*) FILTER (WHERE f.status = 'pending')                              AS open,
		       COUNT(*) FILTER (WHERE f.status = 'pending' AND f.due_date < $2::date)    AS overdue
		  FROM paliad.deadlines f
		  JOIN paliad.projects p ON p.id = f.project_id
		 WHERE `+visibilityPredicatePositional("p", 1)+`
		 GROUP BY f.project_id`, userID, today); err != nil {
		return nil, fmt.Errorf("build tree deadline counts: %w", err)
	}
	countByID := make(map[uuid.UUID]deadlineCount, len(counts))
	for _, c := range counts {
		countByID[c.ProjectID] = c
	}

	nodes := make(map[uuid.UUID]*ProjectTreeNode, len(rows))
	for i := range rows {
		c := countByID[rows[i].ID]
		nodes[rows[i].ID] = &ProjectTreeNode{
			Project:          rows[i],
			Children:         []*ProjectTreeNode{},
			OpenDeadlines:    c.Open,
			OverdueDeadlines: c.Overdue,
		}
	}

	// Stitch children into parents. Roots are projects whose parent_id is
	// NULL or whose parent is invisible (orphaned in the user's view) —
	// promote those to root so the user still sees them.
	roots := []*ProjectTreeNode{}
	for _, n := range nodes {
		if n.ParentID == nil {
			roots = append(roots, n)
			continue
		}
		parent, ok := nodes[*n.ParentID]
		if !ok {
			roots = append(roots, n)
			continue
		}
		parent.Children = append(parent.Children, n)
	}

	sortTreeByPath(roots)
	return roots, nil
}

func sortTreeByPath(nodes []*ProjectTreeNode) {
	for i := 1; i < len(nodes); i++ {
		for j := i; j > 0 && nodes[j].Path < nodes[j-1].Path; j-- {
			nodes[j], nodes[j-1] = nodes[j-1], nodes[j]
		}
	}
	for _, n := range nodes {
		sortTreeByPath(n.Children)
	}
}

// GetTree returns every Project in the subtree rooted at id (inclusive),
// ordered depth-first. Visibility-checked at root; descendants that the
// user can see are returned (the predicate naturally gates sub-branches).
func (s *ProjectService) GetTree(ctx context.Context, userID, id uuid.UUID) ([]models.Project, error) {
	root, err := s.GetByID(ctx, userID, id)
	if err != nil {
		return nil, err
	}
	// path LIKE root.path || '.%' OR path = root.path
	prefix := root.Path + ".%"
	query := `SELECT ` + projektColumns + ` FROM paliad.projects p
	          WHERE (p.path = $1 OR p.path LIKE $2)
	            AND ` + visibilityPredicatePositional("p", 3) + `
	          ORDER BY p.path`
	rows := []models.Project{}
	if err := s.db.SelectContext(ctx, &rows, query, root.Path, prefix, userID); err != nil {
		return nil, fmt.Errorf("get tree: %w", err)
	}
	return rows, nil
}

// Create inserts a new Project. If parent_id is set, the creator must have
// visibility on the parent. The creator is auto-added to project_teams as
// role='lead' in the same transaction so post-create SELECT picks up the row.
func (s *ProjectService) Create(ctx context.Context, userID uuid.UUID, input CreateProjektInput) (*models.Project, error) {
	if strings.TrimSpace(input.Title) == "" {
		return nil, fmt.Errorf("%w: title is required", ErrInvalidInput)
	}
	if !isValidProjectType(input.Type) {
		return nil, fmt.Errorf("%w: invalid type %q", ErrInvalidInput, input.Type)
	}
	user, err := s.users.GetByID(ctx, userID)
	if err != nil {
		return nil, err
	}
	if user == nil {
		return nil, fmt.Errorf("%w: user has no paliad.users row — onboarding required", ErrForbidden)
	}
	if input.ParentID != nil {
		if _, err := s.GetByID(ctx, userID, *input.ParentID); err != nil {
			return nil, fmt.Errorf("%w: parent not visible", ErrForbidden)
		}
	}
	status := input.Status
	if status == "" {
		status = "active"
	}
	if err := validateProjektStatus(status); err != nil {
		return nil, err
	}

	tx, err := s.db.BeginTxx(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("begin tx: %w", err)
	}
	defer tx.Rollback()

	id := uuid.New()
	now := time.Now().UTC()

	// path is NOT NULL but the trigger populates it; supply a placeholder
	// the trigger will overwrite. (BEFORE INSERT trigger rewrites path.)
	if _, err := tx.ExecContext(ctx,
		`INSERT INTO paliad.projects
		    (id, type, parent_id, path, title, reference, description, status,
		     created_by, industry, country, billing_reference, client_number,
		     matter_number, netdocuments_url, patent_number, filing_date, grant_date,
		     court, case_number, proceeding_type_id, metadata, created_at, updated_at)
		 VALUES ($1, $2, $3, $1::text, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13,
		         $14, $15, $16, $17, $18, $19, $20, '{}'::jsonb, $21, $21)`,
		id, input.Type, input.ParentID,
		input.Title, input.Reference, input.Description, status,
		userID,
		input.Industry, input.Country, input.BillingReference,
		input.ClientNumber, input.MatterNumber, input.NetDocumentsURL,
		input.PatentNumber, input.FilingDate, input.GrantDate,
		input.Court, input.CaseNumber, input.ProceedingTypeID,
		now,
	); err != nil {
		return nil, fmt.Errorf("insert project: %w", err)
	}

	// Auto-add creator as team lead so they (and RLS) can see the row.
	if _, err := tx.ExecContext(ctx,
		`INSERT INTO paliad.project_teams (project_id, user_id, role, inherited, added_by)
		 VALUES ($1, $2, 'lead', false, $2)`, id, userID); err != nil {
		return nil, fmt.Errorf("insert creator team row: %w", err)
	}

	if err := insertProjectEvent(ctx, tx, id, userID, "project_created", "Project created", nil); err != nil {
		return nil, err
	}
	if err := tx.Commit(); err != nil {
		return nil, fmt.Errorf("commit create project: %w", err)
	}
	return s.GetByID(ctx, userID, id)
}

// Update applies a partial update. Reparenting triggers path rewrite for the
// subtree (handled by the AFTER UPDATE trigger on paliad.projects).
func (s *ProjectService) Update(ctx context.Context, userID, id uuid.UUID, input UpdateProjektInput) (*models.Project, error) {
	current, err := s.GetByID(ctx, userID, id)
	if err != nil {
		return nil, err
	}
	if input.ParentID != nil {
		// Verify new parent is visible (reparenting under invisible node would
		// leak the whole subtree to the new parent's team — reject).
		if _, err := s.GetByID(ctx, userID, *input.ParentID); err != nil {
			return nil, fmt.Errorf("%w: new parent not visible", ErrForbidden)
		}
	}

	// Type change: validate up-front and collect the columns that were
	// specific to the old type. Those get force-NULL'd at the end of the SET
	// list and the per-field appendSet calls below skip them — Postgres
	// rejects duplicate column assignments in a single UPDATE, and the
	// type-change clear has to win regardless of what the client sent.
	typeChanged := false
	clearOnTypeChange := map[string]bool{}
	if input.Type != nil && *input.Type != current.Type {
		if !isValidProjectType(*input.Type) {
			return nil, fmt.Errorf("%w: invalid type %q", ErrInvalidInput, *input.Type)
		}
		for _, col := range typeSpecificColumns(current.Type) {
			clearOnTypeChange[col] = true
		}
		typeChanged = true
	}

	sets := []string{}
	args := []any{}
	next := 1
	appendSet := func(col string, val any) {
		sets = append(sets, fmt.Sprintf("%s = $%d", col, next))
		args = append(args, val)
		next++
	}
	// appendSetSkippable is for per-field user input that must yield to the
	// type-change clear when the column is being forced to NULL.
	appendSetSkippable := func(col string, val any) {
		if clearOnTypeChange[col] {
			return
		}
		appendSet(col, val)
	}

	if typeChanged {
		appendSet("type", *input.Type)
	}
	if input.Title != nil {
		t := strings.TrimSpace(*input.Title)
		if t == "" {
			return nil, fmt.Errorf("%w: title cannot be empty", ErrInvalidInput)
		}
		appendSet("title", t)
	}
	if input.Reference != nil {
		appendSet("reference", *input.Reference)
	}
	if input.Description != nil {
		appendSet("description", *input.Description)
	}
	if input.Status != nil {
		if err := validateProjektStatus(*input.Status); err != nil {
			return nil, err
		}
		appendSet("status", *input.Status)
	}
	if input.ParentID != nil {
		appendSet("parent_id", *input.ParentID)
	}
	if input.Industry != nil {
		appendSetSkippable("industry", *input.Industry)
	}
	if input.Country != nil {
		appendSetSkippable("country", *input.Country)
	}
	if input.BillingReference != nil {
		appendSet("billing_reference", *input.BillingReference)
	}
	if input.ClientNumber != nil {
		appendSetSkippable("client_number", *input.ClientNumber)
	}
	if input.MatterNumber != nil {
		appendSet("matter_number", *input.MatterNumber)
	}
	if input.NetDocumentsURL != nil {
		appendSet("netdocuments_url", *input.NetDocumentsURL)
	}
	if input.PatentNumber != nil {
		appendSetSkippable("patent_number", *input.PatentNumber)
	}
	if input.FilingDate != nil {
		appendSetSkippable("filing_date", *input.FilingDate)
	}
	if input.GrantDate != nil {
		appendSetSkippable("grant_date", *input.GrantDate)
	}
	if input.Court != nil {
		appendSetSkippable("court", *input.Court)
	}
	if input.CaseNumber != nil {
		appendSetSkippable("case_number", *input.CaseNumber)
	}
	if input.ProceedingTypeID != nil {
		appendSetSkippable("proceeding_type_id", *input.ProceedingTypeID)
	}
	if typeChanged {
		for _, col := range typeSpecificColumns(current.Type) {
			appendSet(col, nil)
		}
	}
	if len(sets) == 0 {
		return current, nil
	}
	appendSet("updated_at", time.Now().UTC())

	args = append(args, id)
	query := fmt.Sprintf("UPDATE paliad.projects SET %s WHERE id = $%d",
		strings.Join(sets, ", "), next)

	tx, err := s.db.BeginTxx(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("begin tx: %w", err)
	}
	defer tx.Rollback()

	if _, err := tx.ExecContext(ctx, query, args...); err != nil {
		return nil, fmt.Errorf("update project: %w", err)
	}

	if input.Status != nil && *input.Status != current.Status {
		desc := fmt.Sprintf("Status %s → %s", current.Status, *input.Status)
		descPtr := &desc
		if err := insertProjectEvent(ctx, tx, id, userID, "status_changed", "Status changed", descPtr); err != nil {
			return nil, err
		}
	}
	if typeChanged {
		desc := fmt.Sprintf("Type %s → %s", current.Type, *input.Type)
		descPtr := &desc
		if err := insertProjectEvent(ctx, tx, id, userID, "project_type_changed", "Project type changed", descPtr); err != nil {
			return nil, err
		}
	}
	if input.ParentID != nil {
		if err := insertProjectEvent(ctx, tx, id, userID, "project_reparented", "Project re-parented", nil); err != nil {
			return nil, err
		}
	}
	if err := tx.Commit(); err != nil {
		return nil, fmt.Errorf("commit update project: %w", err)
	}
	return s.GetByID(ctx, userID, id)
}

// Delete archives the Project (soft-delete, status='archived'). Partner/admin only.
// Hard-delete cascades through FK; we prefer archival for audit.
func (s *ProjectService) Delete(ctx context.Context, userID, id uuid.UUID) error {
	user, err := s.users.GetByID(ctx, userID)
	if err != nil {
		return err
	}
	if user == nil {
		return ErrNotVisible
	}
	if user.GlobalRole != "global_admin" {
		return fmt.Errorf("%w: only partners/admins can archive Projects", ErrForbidden)
	}
	if _, err := s.GetByID(ctx, userID, id); err != nil {
		return err
	}

	tx, err := s.db.BeginTxx(ctx, nil)
	if err != nil {
		return fmt.Errorf("begin tx: %w", err)
	}
	defer tx.Rollback()

	res, err := tx.ExecContext(ctx,
		`UPDATE paliad.projects SET status = 'archived', updated_at = $1
		  WHERE id = $2 AND status != 'archived'`, time.Now().UTC(), id)
	if err != nil {
		return fmt.Errorf("archive project: %w", err)
	}
	if rows, _ := res.RowsAffected(); rows == 0 {
		return tx.Commit()
	}
	if err := insertProjectEvent(ctx, tx, id, userID, "project_archived", "Project archived", nil); err != nil {
		return err
	}
	return tx.Commit()
}

// MaxEventsPageLimit caps ListEvents page size.
const MaxEventsPageLimit = 200

// DefaultEventsPageLimit is the page size when ?limit= is omitted.
const DefaultEventsPageLimit = 50

// ListEvents returns the audit trail for the Project, newest first, with
// cursor pagination (before = uuid of last seen event).
func (s *ProjectService) ListEvents(ctx context.Context, userID, id uuid.UUID, before *uuid.UUID, limit int) ([]models.ProjectEvent, error) {
	if _, err := s.GetByID(ctx, userID, id); err != nil {
		return nil, err
	}
	if limit <= 0 {
		limit = DefaultEventsPageLimit
	}
	if limit > MaxEventsPageLimit {
		limit = MaxEventsPageLimit
	}
	var beforeArg any
	if before != nil {
		beforeArg = *before
	}
	var events []models.ProjectEvent
	err := s.db.SelectContext(ctx, &events,
		`SELECT id, project_id, event_type, title, description, event_date,
		        created_by, metadata, created_at, updated_at
		   FROM paliad.project_events
		  WHERE project_id = $1
		    AND ($2::uuid IS NULL OR (created_at, id) < (
		          SELECT created_at, id FROM paliad.project_events WHERE id = $2::uuid
		    ))
		  ORDER BY created_at DESC, id DESC
		  LIMIT $3`, id, beforeArg, limit)
	if err != nil {
		return nil, fmt.Errorf("list project events: %w", err)
	}
	return events, nil
}

// ResolveClientNumber walks up the path to find the first non-null client_number
// (inherited convention). Returns nil if none in the ancestor chain.
func (s *ProjectService) ResolveClientNumber(ctx context.Context, userID, id uuid.UUID) (*string, error) {
	p, err := s.GetByID(ctx, userID, id)
	if err != nil {
		return nil, err
	}
	if p.ClientNumber != nil {
		return p.ClientNumber, nil
	}
	ancestors, err := s.ListAncestors(ctx, userID, id)
	if err != nil {
		return nil, err
	}
	// Ancestors returned root→parent; scan from closest ancestor outward —
	// but client_number is conceptually set at the root, so walking either
	// direction is fine. Closest wins for override.
	for i := len(ancestors) - 1; i >= 0; i-- {
		if ancestors[i].ClientNumber != nil {
			return ancestors[i].ClientNumber, nil
		}
	}
	return nil, nil
}

// ============================================================================
// Helpers
// ============================================================================

// insertProjectEvent appends one audit row in the given tx.
func insertProjectEvent(ctx context.Context, tx *sqlx.Tx, projektID, userID uuid.UUID, eventType, title string, description *string) error {
	now := time.Now().UTC()
	meta := json.RawMessage(`{}`)
	_, err := tx.ExecContext(ctx,
		`INSERT INTO paliad.project_events
		    (id, project_id, event_type, title, description, event_date,
		     created_by, metadata, created_at, updated_at)
		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $6, $6)`,
		uuid.New(), projektID, eventType, title, description, now, userID, meta)
	if err != nil {
		return fmt.Errorf("insert projekt_event: %w", err)
	}
	return nil
}

// typeSpecificColumns returns the DB columns that only make sense for the
// given project type. When a project's type changes away from `t`, callers
// NULL these columns so the row doesn't carry stale data from the old type.
// Litigation/project have no specific columns.
func typeSpecificColumns(t string) []string {
	switch t {
	case ProjectTypeClient:
		return []string{"industry", "country", "client_number"}
	case ProjectTypePatent:
		return []string{"patent_number", "filing_date", "grant_date"}
	case ProjectTypeCase:
		return []string{"court", "case_number", "proceeding_type_id"}
	}
	return nil
}

func isValidProjectType(t string) bool {
	switch t {
	case ProjectTypeClient, ProjectTypeLitigation, ProjectTypePatent,
		ProjectTypeCase, ProjectTypeProject:
		return true
	}
	return false
}

func validateProjektStatus(s string) error {
	switch s {
	case "active", "archived", "closed":
		return nil
	}
	return fmt.Errorf("%w: invalid status %q", ErrInvalidInput, s)
}

func sortByOrder(xs []models.Project, order map[uuid.UUID]int) {
	// Insertion sort — ancestor lists are short (<20).
	for i := 1; i < len(xs); i++ {
		for j := i; j > 0 && order[xs[j].ID] < order[xs[j-1].ID]; j-- {
			xs[j], xs[j-1] = xs[j-1], xs[j]
		}
	}
}