Add support for subsetting by section heading (#28)

README.md

@@ -134,8 +134,8 @@ code blocks are nested within an unordered list:
 ## Sections and subsections
 
 The section above is 1.3, counting by headings.  It has two subsections
-(1.3.1 and 1.3.2).  We can specify a section to extract the content from
-just that section:
+(1.3.1 and 1.3.2).  We can specify a section number to extract the
+content from just that section:
 
 ```
 $ cat README.md | codedown haskell --section 1.3
@@ -158,6 +158,14 @@ main :: IO ()
 main = putStrLn $ show x
 ```
 
+We can also specify a section by heading:
+
+```
+cat README.md | ./codedown.js haskell --section '### Variables in different languages'
+x :: Int
+x = 42
+```
+
 ## Wildcard matching
 
 Codedown can use wildcards to match file paths, which are used by some

lib/codedown.js

@@ -6,7 +6,7 @@
   var readline  = root.readline || require('readline');
   var minimatch = root.minimatch || require("minimatch");
 
-  var codedown = function(src, lang, separator, section) {
+  var codedown = function(src, lang, separator, targetSection) {
 
     if (separator === undefined) {
       separator = '';
@@ -26,15 +26,43 @@
       }
     }
 
-    var tracker = [];
+    var currentSectionNumber = [];
+    var currentSectionName = null;
+    var sectionNumbers = {};
+
+    var sectionNumberMatches =
+      function () {
+        return currentSectionNumber.join('.').startsWith(targetSection);
+      };
+
+    var sectionNameMatches =
+      function () {
+        return sectionNumbers[targetSection] &&
+          sectionNumbers[currentSectionName].startsWith(sectionNumbers[targetSection]);
+      };
+
+    var sectionMatches =
+      function () {
+        return !targetSection || sectionNumberMatches() || sectionNameMatches();
+      };
+
+    var languageMatches =
+      function (language) {
+        return language && minimatch(language, lang);
+      };
 
     renderer.heading =
       function(text, level, raw) {
         var index = level - 1; // 0-based indexing
         for (var i = 0; i <= index;  i++) {
-          tracker[i] = tracker[i] || 0;
+          currentSectionNumber[i] = currentSectionNumber[i] || 0;
         }
-        tracker[index] = tracker[index] + 1;
+        currentSectionNumber[index] = currentSectionNumber[index] + 1;
+        currentSectionNumber.splice(level);
+
+        currentSectionName = ('#'.repeat(level) + ' ' + raw).trim();
+        sectionNumbers[currentSectionName] = currentSectionNumber.join('.');
+
         return '';
       };
 
@@ -43,10 +71,7 @@
 
         var result = '';
 
-        if (
-          language && minimatch(language, lang) &&
-          (!section || tracker.join('.').startsWith(section))
-        ) {
+        if (languageMatches(language) && sectionMatches()) {
           result = separator + src + '\n';
         }
 

test/codedown.js

@@ -80,7 +80,7 @@ describe('codedown', function(){
     });
   });
 
-  it('should extract code by section (1)', function (done) {
+  it('should extract code by section number (1)', function (done) {
     process.exec('cat README.md | ./codedown.js haskell --section 1', function (err, stdout, stderr) {
       if (!err) {
         assert.equal(
@@ -100,7 +100,7 @@ describe('codedown', function(){
     });
   });
 
-  it('should extract code by section (1.3)', function (done) {
+  it('should extract code by section number (1.3)', function (done) {
     process.exec('cat README.md | ./codedown.js haskell --section 1.3', function (err, stdout, stderr) {
       if (!err) {
         assert.equal(
@@ -120,7 +120,7 @@ describe('codedown', function(){
     });
   });
 
-  it('should extract code by section (1.3.1)', function (done) {
+  it('should extract code by section number (1.3.1)', function (done) {
     process.exec('cat README.md | ./codedown.js haskell --section 1.3.1', function (err, stdout, stderr) {
       if (!err) {
         assert.equal(
@@ -137,7 +137,7 @@ describe('codedown', function(){
     });
   });
 
-  it('should extract code by section (1.3.2)', function (done) {
+  it('should extract code by section number (1.3.2)', function (done) {
     process.exec('cat README.md | ./codedown.js haskell --section 1.3.2', function (err, stdout, stderr) {
       if (!err) {
         assert.equal(
@@ -154,4 +154,58 @@ describe('codedown', function(){
     });
   });
 
+  it('should extract code by section name (## Examples)', function (done) {
+    process.exec('cat README.md | ./codedown.js haskell --section "## Examples"', function (err, stdout, stderr) {
+      if (!err) {
+        assert.equal(
+          stdout,
+          [ 'x :: Int'
+          , 'x = 42'
+          , ''
+          , 'main :: IO ()'
+          , 'main = putStrLn $ show x'
+          , ''
+          ].join('\n')
+        );
+        done();
+      } else {
+        console.log(stderr);
+      }
+    });
+  });
+
+  it('should extract code by section name (### Variables in different languages)', function (done) {
+    process.exec('cat README.md | ./codedown.js haskell --section "### Variables in different languages"', function (err, stdout, stderr) {
+      if (!err) {
+        assert.equal(
+          stdout,
+          [ 'x :: Int'
+          , 'x = 42'
+          , ''
+          ].join('\n')
+        );
+        done();
+      } else {
+        console.log(stderr);
+      }
+    });
+  });
+
+  it('should extract code by section name (### Console output in different languages)', function (done) {
+    process.exec('cat README.md | ./codedown.js haskell --section "### Console output in different languages"', function (err, stdout, stderr) {
+      if (!err) {
+        assert.equal(
+          stdout,
+          [ 'main :: IO ()'
+          , 'main = putStrLn $ show x'
+          , ''
+          ].join('\n')
+        );
+        done();
+      } else {
+        console.log(stderr);
+      }
+    });
+  });
+
 });