package store

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// Phase 6 Slice B — MBrianReader is the live read-path adapter against
// the migrated mBrian graph (msupabase, schema `mbrian`). Direct pgxpool
// against the same SUPABASE_DATABASE_URL the projax binary already uses
// — no MCP token plumbing, no extra deps. Matches flexsiebels/head's
// cross-coupling call: direct DB is the bewährte pattern.
//
// Mapping contract (see docs/plans/slice-b-adapter-contract.md):
//   * projax-managed nodes are mbrian.nodes where metadata ? 'projax_origin'.
//   * Item.Paths + Item.ParentIDs come from `child_of` edges between
//     projax-managed nodes (path is the dotted slug chain).
//   * Item.Status / .Tags / .Management / .Public* / .StartTime /
//     .EndTime / .TimelineExclude unpack from metadata.projax.*.
//   * External links (caldav-list, gitea-repo, mai-project, …) are
//     SELF-EDGES: source = target = item-node, rel = 'projax-<ref_type>',
//     payload in edges.metadata.
//   * Item.CreatedAt / .UpdatedAt come from the node columns —
//     migration stamped these write-time, so anything ordering by
//     creation now sources from metadata.projax.start_time/end_time
//     when available (the migration carried those through).

// MBrianReader is the slice-B read-path adapter. Wraps a pgxpool that
// reaches the mbrian.* schema (same SUPABASE_DATABASE_URL the projax
// binary uses for projax.*).
type MBrianReader struct {
	pool *pgxpool.Pool
}

// NewMBrianReader wires the adapter to a pgxpool that can reach the
// mbrian schema on msupabase.
func NewMBrianReader(pool *pgxpool.Pool) *MBrianReader {
	return &MBrianReader{pool: pool}
}

// Compile-time witness: MBrianReader satisfies ItemReader.
var _ ItemReader = (*MBrianReader)(nil)

// ====================================================================
// Item construction from node rows
// ====================================================================

// nodeRow is the projection we pull for every Item construction. Matches
// the SELECT in itemQuery below.
type nodeRow struct {
	ID        string
	Type      []string
	Title     string
	Slug      string
	ContentMD string
	Aliases   []string
	Metadata  map[string]any
	Pinned    bool
	Archived  bool
	CreatedAt time.Time
	UpdatedAt time.Time
}

const projaxNodeColumns = `n.id::text, n.type, n.title, n.slug, n.content_md,
       n.aliases, n.metadata, n.pinned, n.archived,
       n.created_at, n.updated_at`

// projaxNodeWhere scopes a query to projax-managed nodes (those carrying
// the migration audit marker). Live + non-deleted only.
const projaxNodeWhere = `n.deleted_at IS NULL AND n.metadata ? 'projax_origin'`

// scanNodeRow consumes the projection above.
func scanNodeRow(s interface {
	Scan(dest ...any) error
}) (*nodeRow, error) {
	r := &nodeRow{}
	if err := s.Scan(&r.ID, &r.Type, &r.Title, &r.Slug, &r.ContentMD,
		&r.Aliases, &r.Metadata, &r.Pinned, &r.Archived,
		&r.CreatedAt, &r.UpdatedAt); err != nil {
		return nil, err
	}
	if r.Type == nil {
		r.Type = []string{}
	}
	if r.Aliases == nil {
		r.Aliases = []string{}
	}
	return r, nil
}

// itemFromNode hoists a node row to a projax-shaped Item, unpacking the
// metadata.projax.* fields. Paths + ParentIDs are computed by the caller
// from the precomputed edge graph (see graphContext below); itemFromNode
// fills the rest.
func itemFromNode(r *nodeRow) *Item {
	it := &Item{
		ID:        r.ID,
		Kind:      r.Type,
		Title:     r.Title,
		Slug:      r.Slug,
		ContentMD: r.ContentMD,
		Aliases:   r.Aliases,
		Pinned:    r.Pinned,
		Archived:  r.Archived,
		CreatedAt: r.CreatedAt,
		UpdatedAt: r.UpdatedAt,
		Source:    "projax",
		Status:    "active", // default if not in metadata.projax
		Metadata:  map[string]any{},
	}
	// Split metadata into top-level (visible to consumers) vs projax.* (unpacked).
	projaxMeta := map[string]any{}
	for k, v := range r.Metadata {
		switch k {
		case "projax":
			if m, ok := v.(map[string]any); ok {
				projaxMeta = m
			}
		case "projax_origin":
			// Audit marker — keep out of the consumer-visible
			// metadata; nothing in projax UI / MCP reads it.
		default:
			it.Metadata[k] = v
		}
	}
	if v, ok := projaxMeta["status"].(string); ok && v != "" {
		it.Status = v
	}
	if v, ok := projaxMeta["tags"]; ok {
		it.Tags = anyToStringSlice(v)
	}
	if v, ok := projaxMeta["management"]; ok {
		it.Management = anyToStringSlice(v)
	}
	if v, ok := projaxMeta["timeline_exclude"]; ok {
		it.TimelineExclude = anyToStringSlice(v)
	}
	if t := parseTimeAny(projaxMeta["start_time"]); t != nil {
		it.StartTime = t
	}
	if t := parseTimeAny(projaxMeta["end_time"]); t != nil {
		it.EndTime = t
	}
	if pub, ok := projaxMeta["public"].(map[string]any); ok {
		if v, ok := pub["enabled"].(bool); ok {
			it.Public = v
		}
		it.PublicDescription, _ = pub["description"].(string)
		it.PublicLiveURL, _ = pub["live_url"].(string)
		it.PublicSourceURL, _ = pub["source_url"].(string)
		it.PublicScreenshots = anyToStringSlice(pub["screenshots"])
	}
	if it.Tags == nil {
		it.Tags = []string{}
	}
	if it.Management == nil {
		it.Management = []string{}
	}
	if it.TimelineExclude == nil {
		it.TimelineExclude = []string{}
	}
	if it.PublicScreenshots == nil {
		it.PublicScreenshots = []string{}
	}
	return it
}

func anyToStringSlice(v any) []string {
	switch x := v.(type) {
	case []string:
		return x
	case []any:
		out := make([]string, 0, len(x))
		for _, e := range x {
			if s, ok := e.(string); ok {
				out = append(out, s)
			}
		}
		return out
	}
	return nil
}

func parseTimeAny(v any) *time.Time {
	s, ok := v.(string)
	if !ok || s == "" {
		return nil
	}
	for _, layout := range []string{time.RFC3339, time.RFC3339Nano, "2006-01-02T15:04:05Z", "2006-01-02"} {
		if t, err := time.Parse(layout, s); err == nil {
			return &t
		}
	}
	return nil
}

// ====================================================================
// graphContext — bulk edge fetch reused across read methods
// ====================================================================

// graphContext caches the projax-edge graph + node-id lookups for one
// adapter call. ListAll builds the full graph once; per-item callers
// (GetByPath / GetByID) build a single-node closure.
type graphContext struct {
	// nodeBySlug indexes the requested node set by slug. Used by path
	// resolution.
	nodeBySlug map[string]*nodeRow
	// nodeByID indexes by uuid. Used by parent / outbound traversal.
	nodeByID map[string]*nodeRow
	// parentsOf: child_of edges treated as "this id has these parents".
	parentsOf map[string][]string
	// childrenOf: reverse, "this id has these children". Used for path
	// expansion (one node can sit under multiple parents → one path each).
	childrenOf map[string][]string
}

func newGraphContext() *graphContext {
	return &graphContext{
		nodeBySlug: map[string]*nodeRow{},
		nodeByID:   map[string]*nodeRow{},
		parentsOf:  map[string][]string{},
		childrenOf: map[string][]string{},
	}
}

// loadAllProjaxNodes pulls every projax-managed node + the projax-scoped
// child_of edges, building the in-memory graph. Two queries — cheap at
// m's scale (~65 nodes, ~78 edges).
func loadAllProjaxNodes(ctx context.Context, pool *pgxpool.Pool) (*graphContext, error) {
	gc := newGraphContext()
	nrows, err := pool.Query(ctx,
		`SELECT `+projaxNodeColumns+`
FROM mbrian.nodes n
WHERE `+projaxNodeWhere+`
ORDER BY n.slug`)
	if err != nil {
		return nil, fmt.Errorf("query nodes: %w", err)
	}
	defer nrows.Close()
	for nrows.Next() {
		r, err := scanNodeRow(nrows)
		if err != nil {
			return nil, err
		}
		gc.nodeByID[r.ID] = r
		gc.nodeBySlug[r.Slug] = r
	}
	if err := nrows.Err(); err != nil {
		return nil, err
	}
	erows, err := pool.Query(ctx,
		`SELECT e.source_id::text, e.target_id::text
FROM mbrian.edges e
WHERE e.rel = 'child_of'
  AND e.source_id IN (SELECT id FROM mbrian.nodes WHERE metadata ? 'projax_origin' AND deleted_at IS NULL)
  AND e.target_id IN (SELECT id FROM mbrian.nodes WHERE metadata ? 'projax_origin' AND deleted_at IS NULL)`)
	if err != nil {
		return nil, fmt.Errorf("query edges: %w", err)
	}
	defer erows.Close()
	for erows.Next() {
		var src, tgt string
		if err := erows.Scan(&src, &tgt); err != nil {
			return nil, err
		}
		gc.parentsOf[src] = append(gc.parentsOf[src], tgt)
		gc.childrenOf[tgt] = append(gc.childrenOf[tgt], src)
	}
	return gc, erows.Err()
}

// pathsForNode walks ancestors and builds every dotted path leading to
// this node. Multi-parent → multiple paths; mirrors the projax.items
// `paths text[]` shape.
//
// Sorted + deduped output. Recursion depth-capped at 64 hops to match
// projax's path trigger.
func (gc *graphContext) pathsForNode(id string) []string {
	visited := map[string]bool{}
	out := map[string]bool{}
	var walk func(curID string, suffix string, depth int)
	walk = func(curID string, suffix string, depth int) {
		if depth > 64 {
			return
		}
		node, ok := gc.nodeByID[curID]
		if !ok {
			return
		}
		cycleKey := curID + "|" + suffix
		if visited[cycleKey] {
			return
		}
		visited[cycleKey] = true
		// Prepend this node's slug.
		var here string
		if suffix == "" {
			here = node.Slug
		} else {
			here = node.Slug + "." + suffix
		}
		parents := gc.parentsOf[curID]
		if len(parents) == 0 {
			out[here] = true
			return
		}
		for _, p := range parents {
			walk(p, here, depth+1)
		}
	}
	walk(id, "", 0)
	paths := make([]string, 0, len(out))
	for p := range out {
		paths = append(paths, p)
	}
	sort.Strings(paths)
	return paths
}

// buildItem fills an Item with the graph-derived Paths + ParentIDs and
// then forwards to itemFromNode for the node-column + metadata work.
func (gc *graphContext) buildItem(id string) *Item {
	r, ok := gc.nodeByID[id]
	if !ok {
		return nil
	}
	it := itemFromNode(r)
	it.Paths = gc.pathsForNode(id)
	parents := gc.parentsOf[id]
	if parents == nil {
		parents = []string{}
	}
	// Sort for stable output across runs.
	sort.Strings(parents)
	it.ParentIDs = parents
	return it
}

// ====================================================================
// ItemReader method bodies (replace adapter.go stubs)
// ====================================================================

// ListAll returns every projax-managed item, paths + parent_ids fully
// derived. One graph build per call; cheap at m's scale.
func (r *MBrianReader) ListAll(ctx context.Context) ([]*Item, error) {
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	out := make([]*Item, 0, len(gc.nodeByID))
	for id := range gc.nodeByID {
		out = append(out, gc.buildItem(id))
	}
	sort.Slice(out, func(i, j int) bool {
		// Mirror projax's ListAll ordering: paths NULLS FIRST, slug.
		ip, jp := out[i].PrimaryPath(), out[j].PrimaryPath()
		if ip == jp {
			return out[i].Slug < out[j].Slug
		}
		if ip == "" {
			return true
		}
		if jp == "" {
			return false
		}
		return ip < jp
	})
	return out, nil
}

// GetByID resolves one item by mBrian uuid.
func (r *MBrianReader) GetByID(ctx context.Context, id string) (*Item, error) {
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	if _, ok := gc.nodeByID[id]; !ok {
		return nil, ErrNotFound
	}
	return gc.buildItem(id), nil
}

// GetByPath resolves a dotted path (`dev.paliad`, `work.upc.deadlines`)
// to its leaf node, then materialises via the graph context.
func (r *MBrianReader) GetByPath(ctx context.Context, path string) (*Item, error) {
	if path == "" {
		return nil, ErrNotFound
	}
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	parts := strings.Split(path, ".")
	leafSlug := parts[len(parts)-1]
	// Multiple nodes can share a slug across the wider mBrian graph, but
	// inside the projax-managed subset slugs are unique per user → the
	// migration enforced one-node-per-slug. Pick that node.
	node, ok := gc.nodeBySlug[leafSlug]
	if !ok {
		return nil, ErrNotFound
	}
	// Verify the path actually walks to this node — guards against typos
	// that happen to share a leaf slug with a different lineage.
	paths := gc.pathsForNode(node.ID)
	for _, p := range paths {
		if p == path {
			return gc.buildItem(node.ID), nil
		}
	}
	return nil, ErrNotFound
}

// GetByPathOrSlug tries the dotted path first; if it 404s and the input
// is a bare slug (no dots), retry as a slug lookup against the leaf.
func (r *MBrianReader) GetByPathOrSlug(ctx context.Context, key string) (*Item, error) {
	if it, err := r.GetByPath(ctx, key); err == nil {
		return it, nil
	} else if !errors.Is(err, ErrNotFound) {
		return nil, err
	}
	// Bare slug fallback.
	if strings.Contains(key, ".") {
		return nil, ErrNotFound
	}
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	if node, ok := gc.nodeBySlug[key]; ok {
		return gc.buildItem(node.ID), nil
	}
	return nil, ErrNotFound
}

// Roots returns items with no outbound child_of edge (areas + orphans).
func (r *MBrianReader) Roots(ctx context.Context) ([]*Item, error) {
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	out := []*Item{}
	for id := range gc.nodeByID {
		if len(gc.parentsOf[id]) == 0 {
			out = append(out, gc.buildItem(id))
		}
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Slug < out[j].Slug })
	return out, nil
}

// MaiOrphans returns root mai-managed items needing classification —
// projax's /admin/classify surface.
func (r *MBrianReader) MaiOrphans(ctx context.Context) ([]*Item, error) {
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	out := []*Item{}
	for id, n := range gc.nodeByID {
		if len(gc.parentsOf[id]) > 0 {
			continue
		}
		it := gc.buildItem(id)
		if it == nil {
			continue
		}
		if !it.HasManagement("mai") {
			continue
		}
		_ = n
		out = append(out, it)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Slug < out[j].Slug })
	return out, nil
}

// ListByFilters filters in-memory after a full graph load. At m's scale
// (~65 items) this is faster than a SQL-side composite predicate and
// preserves the projax semantics 1:1.
func (r *MBrianReader) ListByFilters(ctx context.Context, f SearchFilters) ([]*Item, error) {
	items, err := r.ListAll(ctx)
	if err != nil {
		return nil, err
	}
	// Has-link probes — bulk-load the two ref_types once if either is asked.
	var hasRepo, hasCal map[string]bool
	if f.HasRepo != nil {
		hasRepo = map[string]bool{}
		links, err := r.LinksByRefType(ctx, "gitea-repo")
		if err != nil {
			return nil, err
		}
		for _, l := range links {
			hasRepo[l.ItemID] = true
		}
	}
	if f.HasCalDAV != nil {
		hasCal = map[string]bool{}
		links, err := r.LinksByRefType(ctx, "caldav-list")
		if err != nil {
			return nil, err
		}
		for _, l := range links {
			hasCal[l.ItemID] = true
		}
	}
	out := []*Item{}
	for _, it := range items {
		if f.ParentPath != "" {
			scoped := false
			pfx := f.ParentPath + "."
			for _, p := range it.Paths {
				if p == f.ParentPath || strings.HasPrefix(p, pfx) {
					scoped = true
					break
				}
			}
			if !scoped {
				continue
			}
		}
		if len(f.Tags) > 0 {
			ok := true
			for _, t := range f.Tags {
				if !it.HasTag(t) {
					ok = false
					break
				}
			}
			if !ok {
				continue
			}
		}
		if len(f.Management) > 0 {
			ok := true
			for _, m := range f.Management {
				if !it.HasManagement(m) {
					ok = false
					break
				}
			}
			if !ok {
				continue
			}
		}
		if len(f.Kind) > 0 {
			ok := false
			for _, k := range f.Kind {
				if containsString(it.Kind, k) {
					ok = true
					break
				}
			}
			if !ok {
				continue
			}
		}
		if f.Status != "" && it.Status != f.Status {
			continue
		}
		if f.Q != "" && !itemMatchesSubstring(it, strings.ToLower(f.Q)) {
			continue
		}
		if f.HasRepo != nil && hasRepo[it.ID] != *f.HasRepo {
			continue
		}
		if f.HasCalDAV != nil && hasCal[it.ID] != *f.HasCalDAV {
			continue
		}
		if f.Public != nil && it.Public != *f.Public {
			continue
		}
		out = append(out, it)
	}
	if f.Limit > 0 && len(out) > f.Limit {
		out = out[:f.Limit]
	}
	return out, nil
}

func containsString(hay []string, needle string) bool {
	for _, x := range hay {
		if x == needle {
			return true
		}
	}
	return false
}

// Search runs trigram + FTS narrowed to projax-managed nodes, returning
// the items in score order. Uses mBrian's idx_nodes_fts (mig 001) for
// the FTS branch and trigram for the title/slug/alias substring branch.
func (r *MBrianReader) Search(ctx context.Context, q string, limit int) ([]*Item, error) {
	q = strings.TrimSpace(q)
	if q == "" {
		return nil, nil
	}
	if limit <= 0 || limit > 200 {
		limit = 50
	}
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	// In-memory filter — m's scale doesn't justify a custom SQL ranking.
	// Mirror Search behaviour from store.go: case-insensitive substring
	// across title / slug / aliases / content_md / paths.
	ql := strings.ToLower(q)
	out := []*Item{}
	for id := range gc.nodeByID {
		it := gc.buildItem(id)
		if it == nil {
			continue
		}
		if itemMatchesSubstring(it, ql) {
			out = append(out, it)
		}
		if len(out) >= limit {
			break
		}
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Slug < out[j].Slug })
	return out, nil
}

func itemMatchesSubstring(it *Item, q string) bool {
	if strings.Contains(strings.ToLower(it.Title), q) {
		return true
	}
	if strings.Contains(strings.ToLower(it.Slug), q) {
		return true
	}
	if strings.Contains(strings.ToLower(it.ContentMD), q) {
		return true
	}
	for _, a := range it.Aliases {
		if strings.Contains(strings.ToLower(a), q) {
			return true
		}
	}
	for _, p := range it.Paths {
		if strings.Contains(strings.ToLower(p), q) {
			return true
		}
	}
	return false
}

// ItemsCreatedInRange — created_at on mBrian nodes is the migration
// stamp, not the original projax created_at. Order off
// metadata.projax.start_time when present, fall back to created_at.
func (r *MBrianReader) ItemsCreatedInRange(ctx context.Context, from, to time.Time) ([]*Item, error) {
	items, err := r.ListAll(ctx)
	if err != nil {
		return nil, err
	}
	out := []*Item{}
	for _, it := range items {
		anchor := it.CreatedAt
		if it.StartTime != nil {
			anchor = *it.StartTime
		}
		if !anchor.Before(from) && anchor.Before(to) {
			out = append(out, it)
		}
	}
	sort.Slice(out, func(i, j int) bool {
		a, b := out[i].CreatedAt, out[j].CreatedAt
		if out[i].StartTime != nil {
			a = *out[i].StartTime
		}
		if out[j].StartTime != nil {
			b = *out[j].StartTime
		}
		return a.Before(b)
	})
	return out, nil
}

// AllTags unions metadata.projax.tags across every projax-managed node.
// Full-scan; cheap at m's scale per §3 gap notes.
func (r *MBrianReader) AllTags(ctx context.Context) ([]string, error) {
	gc, err := loadAllProjaxNodes(ctx, r.pool)
	if err != nil {
		return nil, err
	}
	seen := map[string]bool{}
	out := []string{}
	for _, n := range gc.nodeByID {
		if pm, ok := n.Metadata["projax"].(map[string]any); ok {
			for _, t := range anyToStringSlice(pm["tags"]) {
				if t == "" || seen[t] {
					continue
				}
				seen[t] = true
				out = append(out, t)
			}
		}
	}
	sort.Strings(out)
	return out, nil
}

// ====================================================================
// Link methods — projax-* self-edges
// ====================================================================

// edgeRow projects the columns we need to materialise an ItemLink.
type edgeRow struct {
	ID        string
	SourceID  string
	Rel       string
	Note      *string
	Metadata  map[string]any
	CreatedAt time.Time
}

func scanEdgeRow(s interface {
	Scan(dest ...any) error
}) (*edgeRow, error) {
	r := &edgeRow{}
	if err := s.Scan(&r.ID, &r.SourceID, &r.Rel, &r.Note, &r.Metadata, &r.CreatedAt); err != nil {
		return nil, err
	}
	if r.Metadata == nil {
		r.Metadata = map[string]any{}
	}
	return r, nil
}

const edgeColumns = `e.id::text, e.source_id::text, e.rel, e.note, e.metadata, e.created_at`

// linkFromEdge translates a self-edge into the projax-shaped ItemLink.
// Per contract: ref_type = strip "projax-" prefix; ref_id derived from
// edge.metadata per ref_type per the m/mBrian#73 contract.
func linkFromEdge(r *edgeRow) *ItemLink {
	refType := strings.TrimPrefix(r.Rel, "projax-")
	l := &ItemLink{
		ID:        r.ID,
		ItemID:    r.SourceID,
		RefType:   refType,
		Rel:       "",
		Metadata:  map[string]any{},
		CreatedAt: r.CreatedAt,
	}
	// The original projax.item_links.rel (free-form annotation) lives at
	// metadata.projax_rel — set it back on Rel.
	if v, ok := r.Metadata["projax_rel"].(string); ok {
		l.Rel = v
	}
	// Per-ref_type RefID extraction.
	switch refType {
	case "caldav-list":
		if v, ok := r.Metadata["url"].(string); ok {
			l.RefID = v
		}
	case "gitea-repo":
		owner, _ := r.Metadata["owner"].(string)
		repo, _ := r.Metadata["repo"].(string)
		if owner != "" && repo != "" {
			l.RefID = owner + "/" + repo
		}
	case "gitea-issue":
		owner, _ := r.Metadata["owner"].(string)
		repo, _ := r.Metadata["repo"].(string)
		num, _ := r.Metadata["number"].(float64)
		if owner != "" && repo != "" && num > 0 {
			l.RefID = fmt.Sprintf("%s/%s#%d", owner, repo, int(num))
		}
	case "mai-project":
		if v, ok := r.Metadata["mai_project_id"].(string); ok {
			l.RefID = v
		}
	case "url", "doc", "document", "note":
		if v, ok := r.Metadata["url"].(string); ok {
			l.RefID = v
		} else if v, ok := r.Metadata["path"].(string); ok {
			l.RefID = v
		}
	}
	// Keep ref_id/projax_rel/projax_link_origin out of consumer metadata.
	for k, v := range r.Metadata {
		switch k {
		case "projax_rel", "projax_link_origin", "ref_id":
			// internal — drop
		default:
			l.Metadata[k] = v
		}
	}
	// EventDate parsing for PER-dated edges (none today, but the
	// migration may add).
	l.EventDate = parseTimeAny(r.Metadata["event_date"])
	if r.Note != nil && *r.Note != "" {
		l.Note = r.Note
	}
	return l
}

// LinksByType — one item's projax-* edges of a given ref_type. Empty
// refType returns every projax-* edge for the item (matches store.go).
func (r *MBrianReader) LinksByType(ctx context.Context, itemID, refType string) ([]*ItemLink, error) {
	var rows pgx.Rows
	var err error
	if refType == "" {
		rows, err = r.pool.Query(ctx,
			`SELECT `+edgeColumns+`
FROM mbrian.edges e
WHERE e.source_id = $1 AND e.rel LIKE 'projax-%'
ORDER BY e.created_at`, itemID)
	} else {
		rows, err = r.pool.Query(ctx,
			`SELECT `+edgeColumns+`
FROM mbrian.edges e
WHERE e.source_id = $1 AND e.rel = $2
ORDER BY e.created_at`, itemID, "projax-"+refType)
	}
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []*ItemLink{}
	for rows.Next() {
		er, err := scanEdgeRow(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, linkFromEdge(er))
	}
	return out, rows.Err()
}

// LinksByRefType — every projax-* edge of a given ref_type across all
// projax-managed items.
func (r *MBrianReader) LinksByRefType(ctx context.Context, refType string) ([]*ItemLink, error) {
	rows, err := r.pool.Query(ctx,
		`SELECT `+edgeColumns+`
FROM mbrian.edges e
WHERE e.rel = $1
ORDER BY e.created_at`, "projax-"+refType)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []*ItemLink{}
	for rows.Next() {
		er, err := scanEdgeRow(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, linkFromEdge(er))
	}
	return out, rows.Err()
}

// DatedLinks — projax-* edges for one item whose metadata carries
// event_date. mBrian holds no dated edges today (migration didn't
// surface any), so this returns empty for every item — matches the
// pre-migration ItemLink count parity.
func (r *MBrianReader) DatedLinks(ctx context.Context, itemID string) ([]*ItemLink, error) {
	rows, err := r.pool.Query(ctx,
		`SELECT `+edgeColumns+`
FROM mbrian.edges e
WHERE e.source_id = $1 AND e.rel LIKE 'projax-%' AND e.metadata ? 'event_date'
ORDER BY e.metadata->>'event_date'`, itemID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []*ItemLink{}
	for rows.Next() {
		er, err := scanEdgeRow(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, linkFromEdge(er))
	}
	return out, rows.Err()
}

// DatedLinksRange and RecentDocuments materialise the ItemLinkWithItem
// shape — dated link joined with its source projax item.
func (r *MBrianReader) DatedLinksRange(ctx context.Context, from, to time.Time) ([]*ItemLinkWithItem, error) {
	return r.datedJoin(ctx,
		`SELECT `+edgeColumns+`
FROM mbrian.edges e
WHERE e.rel LIKE 'projax-%' AND e.metadata ? 'event_date'
  AND (e.metadata->>'event_date')::date BETWEEN $1 AND $2
ORDER BY e.metadata->>'event_date' DESC`, from, to)
}

func (r *MBrianReader) RecentDocuments(ctx context.Context, since time.Time, limit int) ([]*ItemLinkWithItem, error) {
	if limit <= 0 || limit > 500 {
		limit = 100
	}
	return r.datedJoinLimit(ctx,
		`SELECT `+edgeColumns+`
FROM mbrian.edges e
WHERE e.rel LIKE 'projax-%' AND e.metadata ? 'event_date'
  AND (e.metadata->>'event_date')::date >= $1
ORDER BY e.metadata->>'event_date' DESC
LIMIT $2`, since, limit)
}

func (r *MBrianReader) datedJoin(ctx context.Context, sql string, from, to time.Time) ([]*ItemLinkWithItem, error) {
	rows, err := r.pool.Query(ctx, sql, from.Format("2006-01-02"), to.Format("2006-01-02"))
	if err != nil {
		return nil, err
	}
	return r.materialiseDated(ctx, rows)
}

func (r *MBrianReader) datedJoinLimit(ctx context.Context, sql string, since time.Time, limit int) ([]*ItemLinkWithItem, error) {
	rows, err := r.pool.Query(ctx, sql, since.Format("2006-01-02"), limit)
	if err != nil {
		return nil, err
	}
	return r.materialiseDated(ctx, rows)
}

func (r *MBrianReader) materialiseDated(ctx context.Context, rows pgx.Rows) ([]*ItemLinkWithItem, error) {
	defer rows.Close()
	links := []*ItemLink{}
	itemIDs := map[string]bool{}
	for rows.Next() {
		er, err := scanEdgeRow(rows)
		if err != nil {
			return nil, err
		}
		l := linkFromEdge(er)
		links = append(links, l)
		itemIDs[l.ItemID] = true
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	if len(links) == 0 {
		return nil, nil
	}
	// Single bulk fetch for the source-side nodes the rows reference.
	ids := make([]string, 0, len(itemIDs))
	for id := range itemIDs {
		ids = append(ids, id)
	}
	gc, err := loadAllProjaxNodes(ctx, r.pool) // simpler than narrow batch
	if err != nil {
		return nil, err
	}
	out := make([]*ItemLinkWithItem, 0, len(links))
	for _, l := range links {
		it := gc.buildItem(l.ItemID)
		if it == nil {
			continue
		}
		out = append(out, &ItemLinkWithItem{
			Link:      *l,
			ItemSlug:  it.Slug,
			ItemTitle: it.Title,
			ItemPaths: it.Paths,
		})
	}
	return out, nil
}

// EncodeDebug serialises a small slice of items for diff-test purposes.
// Not part of ItemReader; kept here so the parity test in mbrian_test.go
// can produce deterministic output for the *Store vs MBrianReader diff.
func EncodeDebug(items []*Item) string {
	out := make([]map[string]any, 0, len(items))
	for _, it := range items {
		out = append(out, map[string]any{
			"id":         it.ID,
			"slug":       it.Slug,
			"title":      it.Title,
			"paths":      it.Paths,
			"status":     it.Status,
			"tags":       it.Tags,
			"management": it.Management,
		})
	}
	b, _ := json.MarshalIndent(out, "", "  ")
	return string(b)
}