Added Base() for constructing the base tag <base>; Closes #9

korona/html/attributes.py

@@ -87,5 +87,18 @@
                                'document.',
                 'values': None
             }
+        },
+    'base':
+        {
+            'href': {
+                'description': 'Specifies the base URL for all relative URLs '
+                               'in the page',
+                'values': None
+            },
+            'target': {
+                'description': 'Specifies the default target for all '
+                               'hyperlinks and forms in the page',
+                'values': None
+            }
         }
 }

korona/html/construct.py

@@ -10,7 +10,8 @@
     anchor_tag,
     abbr_tag,
     acronym_tag,
-    bold_tag
+    bold_tag,
+    base_tag
 )
 
 RECTANGLE_SHAPE_COORDINATES = 4
@@ -211,3 +212,40 @@ def __init__(self, text=None):
     def construct_tag(self):
         """Returns the constructed bold tag <b></b>."""
         return bold_tag.render(self.values)
+
+
+class Base(object):
+    """Class for constructing base tag.
+
+    Args:
+        href (str): Specifies the base URL for all relative URLs in the page.
+        target (str): Specifies the default target for all hyperlinks and
+            forms in the page.
+    """
+    def __init__(self, href=None, target=None):
+        # TODO: Add in the main api method where it can check that there
+        # should be only one base tag in the whole html document.
+        self.tag = 'base'
+        self.validate_values(href=href, target=target)
+        self.values = {'href': href, 'target': target}
+
+    def construct_tag(self):
+        """Returns the constructed base tag <base>."""
+        return base_tag.render(self.values)
+
+    def validate_values(self, href, target):
+        """Validates the following:
+            - Either of href or target attribute value is given.
+            - CHeck whether both href and target attribute values are strings
+                or not.
+        """
+        if not href and not target:
+            raise AttributeError('<base>: base tag must have either a href '
+                                 'attribute or a target attribute, or both.')
+
+        if href and not isinstance(href, str):
+            raise ValueError('<base>: href attribute value should be string')
+
+        if target and not isinstance(target, str):
+            raise ValueError('<base>: target attribute value should be '
+                             'string')

korona/templates/html/__init__.py

@@ -4,5 +4,6 @@
     anchor_tag,
     abbr_tag,
     acronym_tag,
-    bold_tag
+    bold_tag,
+    base_tag
 )

korona/templates/html/tags.py

@@ -29,3 +29,8 @@
 bold_tag = env.from_string("""
 <b>{% if text -%} {{ text }} {% endif -%}</b>
 """)
+
+base_tag = env.from_string("""
+<base {% if href -%} href="{{ href }}" {% endif -%}
+      {% if target -%} target="{{ target }}" {% endif -%}>
+""")

tests/test_tags.py

@@ -6,13 +6,15 @@
     A,
     Abbr,
     Acronym,
-    B
+    B,
+    Base
 )
 from korona.templates.html import (
     anchor_tag,
     abbr_tag,
     acronym_tag,
-    bold_tag
+    bold_tag,
+    base_tag
 )
 from korona.lib.utils import validate_tag
 
@@ -152,3 +154,31 @@ def test_construct_bold_tag(attributes):
     """
     bold = B(**attributes)
     assert bold.construct_tag() == bold_tag.render(attributes)
+
+
+@parametrize('attributes', [
+    ({'href': 'www.google.com'}),
+    ({'target': 'abc'}),
+    ({'href': 'www.google.com', 'target': 'abc'})
+])
+def test_construct_base_tag(attributes):
+    """Test for validating whether the base tag is constructed correctly or
+    not.
+    """
+    base = Base(**attributes)
+    assert base.construct_tag() == base_tag.render(attributes)
+
+
+@parametrize('attributes,exception,error_msg', [
+    ({'href': 123}, ValueError, 'value should be string'),
+    ({'target': 123}, ValueError, 'value should be string'),
+    ({'href': None, 'target': None},
+     AttributeError,
+     'either a href attribute or a target attribute, or both')
+])
+def test_construct_base_tag_error(attributes, exception, error_msg):
+    """Test for validating base tag's attributes."""
+    with pytest.raises(exception) as exc:
+        Base(**attributes)
+
+    assert error_msg in str(exc)