Add tools/html-grep.

This tools greps for HTML nodes that have relevants words
pertaining to classes, ids, or tags in themselves or their
parents.

tools/lib/html_grep.py

@@ -0,0 +1,63 @@
+from __future__ import absolute_import
+from __future__ import print_function
+from collections import defaultdict
+from six.moves import range
+
+from .template_parser import html_branches, Token, HtmlTreeBranch
+
+def show_all_branches(fns):
+    # type: (List[str]) -> None
+    for fn in fns:
+        print(fn)
+        text = open(fn).read()
+        branches = html_branches(text)
+        for branch in branches:
+            print(branch.text())
+        print('---')
+
+class Grepper(object):
+    '''
+    A Grepper object is optimized to do repeated
+    searches of words that can be found in our
+    HtmlTreeBranch objects.
+    '''
+
+    def __init__(self, fns):
+        # type: (List[str]) -> None
+        all_branches = [] # type: List[HtmlTreeBranch]
+
+        for fn in fns:
+            branches = html_branches(fn)
+            all_branches += branches
+
+        self.word_dict = defaultdict(set) # type: Dict[str, Set[HtmlTreeBranch]]
+        for b in all_branches:
+            for word in b.words:
+                self.word_dict[word].add(b)
+
+        self.all_branches = set(all_branches)
+
+    def grep(self, word_set):
+        # type: (Set[str]) -> None
+
+        words = list(word_set) # type: List[str]
+
+        if len(words) == 0:
+            matches = self.all_branches
+        else:
+            matches = self.word_dict[words[0]]
+            for i in range(1, len(words)):
+                matches = matches & self.word_dict[words[i]]
+
+        branches = list(matches)
+        branches.sort(key=lambda branch: (branch.fn, branch.line))
+        for branch in branches:
+            print('%s %d' % (branch.fn, branch.line))
+            print(branch.staircase_text())
+            print('')
+
+def grep(fns, words):
+    # type: (List[str], Set[str]) -> None
+    grepper = Grepper(fns)
+    grepper.grep(words)
+