Hello world

internal/match/match.go

@@ -0,0 +1,218 @@
+// Package match filters and ranks lists the way fzf (and snacks.nvim's
+// picker, a port of it) does: fzf's own scoring, so a match at the start
+// of a word or in one run of characters beats letters scattered through a
+// name, and fzf's extended search syntax:
+//
+//	prod db     both terms, in any order
+//	db | pw     either
+//	'prod       exactly "prod", not fuzzy
+//	^kv-  -dev$ starts with / ends with
+//	!test       without "test"
+//
+// ^ and $ anchor to an item's name, the part of it matches count most
+// for (a secret's name rather than the path to it). Lowercase ignores case; an uppercase letter makes that term exact
+// about case (smartcase). Results sort by score, then the shorter text,
+// then their order in the list.
+package match
+
+import (
+	"slices"
+	"strings"
+
+	"github.com/junegunn/fzf/src/algo"
+	"github.com/junegunn/fzf/src/util"
+)
+
+func init() { algo.Init("default") }
+
+// nameBonus is added to a term's score when all its letters are in the
+// item's name rather than in its context (a path, a note), like snacks'
+// filename_bonus: "pass" should find db-password before a secret that
+// only lives in a vault called "passwords".
+const nameBonus = 24
+
+type kind int
+
+const (
+	fuzzy kind = iota
+	exact
+	prefix
+	suffix
+	equal
+)
+
+type term struct {
+	kind          kind
+	inverse       bool
+	caseSensitive bool
+	text          []rune
+}
+
+// Query is a parsed search: every group must match (AND), a group
+// matches when any of its terms does (OR).
+type Query struct {
+	groups [][]term
+}
+
+// Parse reads a search in fzf's extended syntax.
+func Parse(q string) Query {
+	var out Query
+	or := false
+	for _, tok := range strings.Fields(q) {
+		if tok == "|" {
+			or = true
+			continue
+		}
+		t, ok := parseTerm(tok)
+		if !ok {
+			continue
+		}
+		if n := len(out.groups); or && n > 0 {
+			out.groups[n-1] = append(out.groups[n-1], t)
+		} else {
+			out.groups = append(out.groups, []term{t})
+		}
+		or = false
+	}
+	return out
+}
+
+func parseTerm(tok string) (term, bool) {
+	t := term{kind: fuzzy}
+	if s, ok := strings.CutPrefix(tok, "!"); ok {
+		t.inverse, t.kind, tok = true, exact, s
+	}
+	switch {
+	case strings.HasPrefix(tok, "'"):
+		t.kind, tok = exact, tok[1:]
+	case strings.HasPrefix(tok, "^"):
+		t.kind, tok = prefix, tok[1:]
+	}
+	if s, ok := strings.CutSuffix(tok, "$"); ok && s != "" {
+		if t.kind == prefix {
+			t.kind = equal
+		} else {
+			t.kind = suffix
+		}
+		tok = s
+	}
+	if tok == "" {
+		return term{}, false
+	}
+	t.caseSensitive = strings.ToLower(tok) != tok
+	if !t.caseSensitive {
+		tok = strings.ToLower(tok)
+	}
+	t.text = []rune(tok)
+	return t, true
+}
+
+// Empty reports whether the query has no terms: everything matches.
+func (q Query) Empty() bool { return len(q.groups) == 0 }
+
+// Item is a row to match: Text is everything searched, and runes
+// NameStart up to NameEnd of it are the row's name (the rest is context,
+// like a path or a note). Without a name, nothing gets the name bonus.
+type Item struct {
+	Text               string
+	NameStart, NameEnd int
+}
+
+// Hit is a matching item: its index in the list, score, and the rune
+// positions of the matched letters in its Text.
+type Hit struct {
+	Index int
+	Score int
+	Pos   []int
+}
+
+// Rank returns the items matching q, best first.
+func Rank(q Query, items []Item) []Hit {
+	var hits []Hit
+	for i, it := range items {
+		if h, ok := q.match(it); ok {
+			h.Index = i
+			hits = append(hits, h)
+		}
+	}
+	slices.SortStableFunc(hits, func(a, b Hit) int {
+		if a.Score != b.Score {
+			return b.Score - a.Score
+		}
+		return len(items[a.Index].Text) - len(items[b.Index].Text)
+	})
+	return hits
+}
+
+func (q Query) match(it Item) (Hit, bool) {
+	chars := util.ToChars([]byte(it.Text))
+	// ^ and $ anchor to the name: "vaults starting with kv-", not to the
+	// path before it.
+	name := chars
+	if it.NameEnd > 0 {
+		runes := []rune(it.Text)
+		name = util.RunesToChars(runes[it.NameStart:min(it.NameEnd, len(runes))])
+	}
+	var h Hit
+	for _, group := range q.groups {
+		best, matched := 0, false
+		var bestPos []int
+		for _, t := range group {
+			in, offset := &chars, 0
+			if t.kind == prefix || t.kind == suffix || t.kind == equal {
+				in, offset = &name, it.NameStart
+			}
+			score, pos, ok := t.match(in, offset, it.NameStart, it.NameEnd)
+			if ok && (!matched || score > best) {
+				best, bestPos, matched = score, pos, true
+			}
+		}
+		if !matched {
+			return Hit{}, false
+		}
+		h.Score += best
+		h.Pos = append(h.Pos, bestPos...)
+	}
+	slices.Sort(h.Pos)
+	h.Pos = slices.Compact(h.Pos)
+	return h, true
+}
+
+// match matches t in chars, whose first rune is at offset in the item's
+// text: positions are in the text.
+func (t term) match(chars *util.Chars, offset, nameStart, nameEnd int) (int, []int, bool) {
+	fn := algo.FuzzyMatchV2
+	switch t.kind {
+	case exact:
+		fn = algo.ExactMatchNaive
+	case prefix:
+		fn = algo.PrefixMatch
+	case suffix:
+		fn = algo.SuffixMatch
+	case equal:
+		fn = algo.EqualMatch
+	}
+	res, pos := fn(t.caseSensitive, false, true, chars, t.text, !t.inverse, nil)
+	found := res.Start >= 0
+	if t.inverse {
+		return 0, nil, !found
+	}
+	if !found {
+		return 0, nil, false
+	}
+	var p []int
+	if pos != nil {
+		for _, i := range *pos {
+			p = append(p, i+offset)
+		}
+	} else { // prefix, suffix and equal give a range
+		for i := res.Start; i < res.End; i++ {
+			p = append(p, i+offset)
+		}
+	}
+	score := res.Score
+	if len(p) > 0 && slices.Min(p) >= nameStart && slices.Max(p) < nameEnd {
+		score += nameBonus
+	}
+	return score, p, true
+}