feat(brain): cross-wing tunnels — bidirectional wikilinks + auto-detect

Adds the `brain_tunnel` MCP tool and auto-tunnel behaviour for `brain_write`, so concepts that appear in multiple wings become navigable from any of them. New surface in package brain: - WriteTunnel(brainDir, src, tgt) — appends a `## See also` bidirectional wikilink between two notes in different wings. Idempotent (link not duplicated on re-call) and reuses an existing See also section. - DetectTunnels(brainDir, content) — walks brain/wiki/, returns TunnelCandidates for notes whose title appears in content. Tags whole-word case-insensitive hits as Exact=true and substring-only hits as Exact=false. - AutoTunnel(brainDir, src, content) — wraps DetectTunnels: writes cross-wing exact matches, stages fuzzy matches into brain/raw/tunnel-candidates-<YYYY-MM-DD>.md for human review. MCP wiring: - `brain_tunnel` tool: explicit manual link (source, target). - `brain_write` with wing+hall now triggers AutoTunnel on the new content. Failures are logged and never abort the primary write. readTitleAndCreated also humanises the slug fallback (hyphens → spaces) so titleless notes participate in content matching. Closes hyperguild#16. Tests: idempotency, same-wing rejection, missing-note rejection, See-also reuse, exact/fuzzy detection, slug fallback, MCP tool happy path, auto-tunnel hook (cross-wing exact → linked; same-wing → skipped; fuzzy → candidates file).
2026-05-18 21:32:49 +02:00
parent 61b6247df9
commit ddd07ae7eb
7 changed files with 588 additions and 6 deletions
--- a/ingestion/internal/brain/tunnel.go
+++ b/ingestion/internal/brain/tunnel.go
@@ -0,0 +1,286 @@
+package brain
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+// seeAlsoHeader is the markdown heading used to group cross-wing links.
+const seeAlsoHeader = "## See also"
+
+// TunnelCandidate is a cross-wing match surfaced by DetectTunnels. It is
+// not yet a written link — the caller decides whether confidence is high
+// enough to commit it via WriteTunnel.
+type TunnelCandidate struct {
+	// TargetPath is the candidate note's path relative to brainDir
+	// (forward-slashed), e.g. "wiki/hyperguild/decisions/routing.md".
+	TargetPath string
+	// MatchedTerm is the title that matched in the source content.
+	MatchedTerm string
+	// Exact is true when the match was a case-insensitive whole-token
+	// hit on the target's frontmatter title. Fuzzy matches (substring
+	// only) are flagged Exact=false and should not be auto-written.
+	Exact bool
+}
+
+// DetectTunnels scans brain/wiki/ for notes whose title appears in
+// content. Returns one TunnelCandidate per matching note. Exact is true
+// when content contains the title as a whole-word case-insensitive
+// token; false when only a substring matched (caller treats these as
+// fuzzy and should not auto-write them).
+//
+// A note's title is read from YAML frontmatter `title:`; failing that,
+// the filename slug (sans `.md`, hyphens → spaces) is used.
+func DetectTunnels(brainDir, content string) ([]TunnelCandidate, error) {
+	wikiDir := filepath.Join(brainDir, "wiki")
+	if _, err := os.Stat(wikiDir); os.IsNotExist(err) {
+		return nil, nil
+	} else if err != nil {
+		return nil, fmt.Errorf("stat wiki: %w", err)
+	}
+
+	lowerContent := strings.ToLower(content)
+
+	var out []TunnelCandidate
+	err := filepath.WalkDir(wikiDir, func(path string, d os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() || !strings.HasSuffix(path, ".md") || d.Name() == "_index.md" {
+			return nil
+		}
+		title, _ := readTitleAndCreated(path, strings.TrimSuffix(d.Name(), ".md"))
+		needle := strings.ToLower(strings.TrimSpace(title))
+		if needle == "" {
+			return nil
+		}
+		idx := strings.Index(lowerContent, needle)
+		if idx == -1 {
+			return nil
+		}
+		rel, err := filepath.Rel(brainDir, path)
+		if err != nil {
+			return err
+		}
+		out = append(out, TunnelCandidate{
+			TargetPath:  filepath.ToSlash(rel),
+			MatchedTerm: title,
+			Exact:       isWholeWord(lowerContent, idx, len(needle)),
+		})
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// isWholeWord reports whether the substring at [idx, idx+n) in s is
+// bounded by non-alphanumeric characters (or string edges).
+func isWholeWord(s string, idx, n int) bool {
+	left := idx == 0 || !isWordByte(s[idx-1])
+	right := idx+n == len(s) || !isWordByte(s[idx+n])
+	return left && right
+}
+
+func isWordByte(b byte) bool {
+	return (b >= 'a' && b <= 'z') ||
+		(b >= 'A' && b <= 'Z') ||
+		(b >= '0' && b <= '9')
+}
+
+// AutoTunnel runs DetectTunnels against content and, for each
+// candidate, either writes a bidirectional tunnel (when the match is
+// exact and in a different wing) or stages it for human review in
+// brain/raw/tunnel-candidates-<YYYY-MM-DD>.md.
+//
+// sourcePath is the note that originated the content — used to skip
+// self-matches and same-wing tunnels. Errors writing individual
+// tunnels are recorded into the candidates file but never abort the
+// rest of the scan; the caller's primary write has already succeeded
+// and auto-linking is best-effort.
+func AutoTunnel(brainDir, sourcePath, content string) error {
+	srcWing, err := wingOf(sourcePath)
+	if err != nil {
+		return err
+	}
+	candidates, err := DetectTunnels(brainDir, content)
+	if err != nil {
+		return err
+	}
+
+	var fuzzy []TunnelCandidate
+	for _, c := range candidates {
+		if c.TargetPath == sourcePath {
+			continue
+		}
+		tgtWing, err := wingOf(c.TargetPath)
+		if err != nil || tgtWing == srcWing {
+			continue
+		}
+		if !c.Exact {
+			fuzzy = append(fuzzy, c)
+			continue
+		}
+		if err := WriteTunnel(brainDir, sourcePath, c.TargetPath); err != nil {
+			fuzzy = append(fuzzy, c)
+		}
+	}
+	return logFuzzyCandidates(brainDir, sourcePath, fuzzy)
+}
+
+// logFuzzyCandidates appends one row per candidate to
+// brain/raw/tunnel-candidates-<YYYY-MM-DD>.md, creating the file with a
+// header on first write of the day. No-op when the candidate list is empty.
+func logFuzzyCandidates(brainDir, sourcePath string, cs []TunnelCandidate) error {
+	if len(cs) == 0 {
+		return nil
+	}
+	rawDir := filepath.Join(brainDir, "raw")
+	if err := os.MkdirAll(rawDir, 0o755); err != nil {
+		return err
+	}
+	stamp := time.Now().UTC().Format("2006-01-02")
+	path := filepath.Join(rawDir, "tunnel-candidates-"+stamp+".md")
+	existed := fileExists(path)
+	f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+	if !existed {
+		if _, err := f.WriteString("# Tunnel candidates " + stamp + "\n\nFuzzy cross-wing matches surfaced by AutoTunnel. Review and promote to a tunnel via `brain_tunnel` if relevant.\n\n"); err != nil {
+			return err
+		}
+	}
+	for _, c := range cs {
+		line := fmt.Sprintf("- `%s` ↔ `%s` (term: %q)\n", sourcePath, c.TargetPath, c.MatchedTerm)
+		if _, err := f.WriteString(line); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func fileExists(p string) bool {
+	_, err := os.Stat(p)
+	return err == nil
+}
+
+// WriteTunnel appends a bidirectional wikilink between sourcePath and
+// targetPath under a `## See also` section in each note. Paths are
+// relative to brainDir (forward-slashed), e.g. wiki/<wing>/<hall>/<slug>.md.
+//
+// Idempotent: re-calling with the same pair does not duplicate links or
+// section headers. Rejects same-wing pairs (a tunnel is by definition
+// cross-wing) and missing notes.
+func WriteTunnel(brainDir, sourcePath, targetPath string) error {
+	srcWing, err := wingOf(sourcePath)
+	if err != nil {
+		return fmt.Errorf("source: %w", err)
+	}
+	tgtWing, err := wingOf(targetPath)
+	if err != nil {
+		return fmt.Errorf("target: %w", err)
+	}
+	if srcWing == tgtWing {
+		return fmt.Errorf("tunnel must cross wings; got both in %q", srcWing)
+	}
+
+	srcFull := filepath.Join(brainDir, filepath.FromSlash(sourcePath))
+	tgtFull := filepath.Join(brainDir, filepath.FromSlash(targetPath))
+	if _, err := os.Stat(srcFull); err != nil {
+		return fmt.Errorf("source note: %w", err)
+	}
+	if _, err := os.Stat(tgtFull); err != nil {
+		return fmt.Errorf("target note: %w", err)
+	}
+
+	if err := appendSeeAlso(srcFull, wikilinkOf(targetPath)); err != nil {
+		return fmt.Errorf("update source: %w", err)
+	}
+	if err := appendSeeAlso(tgtFull, wikilinkOf(sourcePath)); err != nil {
+		return fmt.Errorf("update target: %w", err)
+	}
+	return nil
+}
+
+// wikilinkOf turns "wiki/<wing>/<hall>/<slug>.md" into "<wing>/<hall>/<slug>"
+// for use inside `[[...]]`.
+func wikilinkOf(relPath string) string {
+	p := strings.TrimSuffix(relPath, ".md")
+	p = strings.TrimPrefix(p, "wiki/")
+	return p
+}
+
+// wingOf extracts the wing segment from a relative wiki path
+// "wiki/<wing>/<hall>/<slug>.md".
+func wingOf(relPath string) (string, error) {
+	parts := strings.Split(relPath, "/")
+	if len(parts) < 4 || parts[0] != "wiki" {
+		return "", fmt.Errorf("not a wiki path: %q", relPath)
+	}
+	if parts[1] == "" {
+		return "", fmt.Errorf("empty wing in path: %q", relPath)
+	}
+	return parts[1], nil
+}
+
+// appendSeeAlso inserts `- [[link]]` under the file's See also section,
+// creating the section if absent. No-op when the link is already present.
+func appendSeeAlso(filePath, link string) error {
+	content, err := os.ReadFile(filePath)
+	if err != nil {
+		return err
+	}
+	wikilink := "[[" + link + "]]"
+	if strings.Contains(string(content), wikilink) {
+		return nil
+	}
+
+	bullet := "- " + wikilink
+
+	if !strings.Contains(string(content), seeAlsoHeader) {
+		// No section yet — append a fresh one. Always emit a trailing
+		// newline so subsequent appends don't merge into the previous line.
+		trimmed := strings.TrimRight(string(content), "\n")
+		out := trimmed + "\n\n" + seeAlsoHeader + "\n\n" + bullet + "\n"
+		return os.WriteFile(filePath, []byte(out), 0o644)
+	}
+
+	// Section exists — splice the bullet in just before the next `## `
+	// heading (or EOF). Reading the file line-by-line keeps this robust
+	// against arbitrary section ordering.
+	var b strings.Builder
+	scanner := bufio.NewScanner(strings.NewReader(string(content)))
+	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
+	inSeeAlso, inserted := false, false
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !inserted && inSeeAlso && strings.HasPrefix(line, "## ") &&
+			strings.TrimSpace(line) != seeAlsoHeader {
+			b.WriteString(bullet)
+			b.WriteByte('\n')
+			b.WriteByte('\n')
+			inserted = true
+		}
+		if strings.TrimSpace(line) == seeAlsoHeader {
+			inSeeAlso = true
+		}
+		b.WriteString(line)
+		b.WriteByte('\n')
+	}
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+	if !inserted {
+		// section was the last thing in the file — just append bullet
+		out := strings.TrimRight(b.String(), "\n") + "\n" + bullet + "\n"
+		return os.WriteFile(filePath, []byte(out), 0o644)
+	}
+	return os.WriteFile(filePath, []byte(b.String()), 0o644)
+}