Work on implementing the fzf algorithm for the choose files kitten

People are more used to that, and it is more optimized for use case of
finding files.

tools/fzf/api.go

@@ -0,0 +1,48 @@
+package fzf
+
+import (
+	"fmt"
+)
+
+var _ = fmt.Print
+
+func NewFuzzyMatcher(scheme Scheme) (ans *FuzzyMatcher) {
+	return new_fuzzy_matcher(scheme)
+}
+
+// Score the specified items using runtime.NumCPU() go routines. This function
+// reports a panic in any worker go routine as a regular error.
+func (m *FuzzyMatcher) Score(items []string, pattern string) (ans []Result, err error) {
+	return m.score(items, pattern, func(item string, pat []rune, pattern_is_ascii bool, slab *slab, as_chars func(string) Chars) Result {
+		c := as_chars(item)
+		return m.score_one(&c, pat, pattern_is_ascii, slab)
+	})
+}
+
+// Clear the cache used ScoreWithCache(). Useful if you change some of the
+// settings used for scoring.
+func (m *FuzzyMatcher) ClearScoreCache() {
+	m.cache_mutex.Lock()
+	m.cache = make(map[string]Result)
+	m.cache_mutex.Unlock()
+}
+
+// Same as Score, except that it uses a cache. Remember to call
+// ClearScoreCache() if you change any scoring settings on this FuzzyMatcher.
+func (m *FuzzyMatcher) ScoreWithCache(items []string, pattern string) (ans []Result, err error) {
+	key_prefix := pattern + "\x00"
+	return m.score(items, pattern, func(item string, pat []rune, pattern_is_ascii bool, slab *slab, as_chars func(string) Chars) Result {
+		key := key_prefix + item
+		m.cache_mutex.Lock()
+		res, found := m.cache[key]
+		m.cache_mutex.Unlock()
+		if !found {
+			c := as_chars(item)
+			res = m.score_one(&c, pat, pattern_is_ascii, slab)
+			m.cache_mutex.Lock()
+			m.cache[key] = res
+			m.cache_mutex.Unlock()
+		}
+		return res
+	})
+}