brain/sqlbrain: implement think

For #94.

Author: zephyrtronium

brain/brain.go

@@ -25,6 +25,10 @@ type Interface interface {
 	//
 	// Yielded closures replace id and suffix with successive messages' contents.
 	// The iterating loop may not call the yielded closure on every iteration.
+	// When it does, it uses the closure fully within each loop, allowing the
+	// sequence to yield the same closure on each call.
+	// Conversely, iterators should expect that the arguments to the closure
+	// will be the same on each iteration and must not retain them.
 	Think(ctx context.Context, tag string, prefix []string) iter.Seq[func(id, suf *[]byte) error]
 
 	// Speak generates a full message and appends it to w.

brain/braintest/thoughts.go

@@ -0,0 +1,16 @@
+package braintest
+
+import "iter"
+
+// Collect gathers all thoughts from a think.
+func Collect(it iter.Seq[func(id, suf *[]byte) error]) (ids, sufs []string, err error) {
+	var id, suf []byte
+	for f := range it {
+		if err := f(&id, &suf); err != nil {
+			return ids, sufs, err
+		}
+		ids = append(ids, string(id))
+		sufs = append(sufs, string(suf))
+	}
+	return ids, sufs, nil
+}

brain/sqlbrain/speak.go

@@ -15,8 +15,58 @@ import (
 
 var prependerPool tpool.Pool[deque.Deque[string]]
 
-func (br *Brain) Think(ctx context.Context, tag string, prefix []string) iter.Seq[func(id *[]byte, suf *[]byte) error] {
-	panic("unimplemented")
+func (br *Brain) Think(ctx context.Context, tag string, prompt []string) iter.Seq[func(id *[]byte, suf *[]byte) error] {
+	return func(yield func(func(id, suf *[]byte) error) bool) {
+		erf := func(err error) { yield(func(id, suf *[]byte) error { return err }) }
+		conn, err := br.db.Take(ctx)
+		defer br.db.Put(conn)
+		if err != nil {
+			erf(fmt.Errorf("couldn't get connection to speak: %w", err))
+			return
+		}
+		var s *sqlite.Stmt
+		if len(prompt) != 0 {
+			s, err = conn.Prepare(`SELECT id, suffix FROM knowledge WHERE tag = :tag AND prefix >= :lower AND prefix < :upper AND LIKELY(deleted IS NULL)`)
+			if err != nil {
+				erf(fmt.Errorf("couldn't prepare term selection: %w", err))
+				return
+			}
+			b := prefix(make([]byte, 0, 128), prompt)
+			b, d := searchbounds(b)
+			s.SetBytes(":lower", b)
+			s.SetBytes(":upper", d)
+		} else {
+			s, err = conn.Prepare(`SELECT id, suffix FROM knowledge WHERE tag = :tag AND prefix = x'00' AND LIKELY(deleted IS NULL)`)
+			if err != nil {
+				erf(fmt.Errorf("couldn't prepare first term selection: %w", err))
+				return
+			}
+		}
+		s.SetText(":tag", tag)
+		f := func(id, suf *[]byte) error {
+			*id = bytecol(*id, s, 0)
+			*suf = bytecol(*suf, s, 1)
+			return nil
+		}
+		for {
+			ok, err := s.Step()
+			if err != nil {
+				erf(fmt.Errorf("couldn't step term selection: %w", err))
+				return
+			}
+			if !ok || !yield(f) {
+				break
+			}
+		}
+	}
+}
+
+func bytecol(d []byte, s *sqlite.Stmt, col int) []byte {
+	n := s.ColumnLen(col)
+	if cap(d) < n {
+		d = make([]byte, n)
+	}
+	return d[:s.ColumnBytes(col, d[:n])]
 }
 
 // Speak generates a full message and appends it to w.