A Changelog class

src/scriv/collect.py

@@ -1,18 +1,13 @@
 """Collecting fragments."""
 
-import datetime
 import logging
-from pathlib import Path
 from typing import Optional
 
 import click
 import click_log
-import jinja2
 
-from .format import get_format_tools
 from .gitinfo import git_add, git_config_bool, git_edit, git_rm
 from .scriv import Scriv
-from .util import cut_at_line
 
 logger = logging.getLogger()
 
@@ -47,46 +42,19 @@ def collect(
     scriv = Scriv()
     logger.info("Collecting from {}".format(scriv.config.fragment_directory))
     frags = scriv.fragments_to_combine()
-    sections = scriv.combine_fragments(frags)
 
-    changelog = Path(scriv.config.output_file)
-    newline = ""
-    if changelog.exists():
-        with changelog.open("r") as f:
-            changelog_text = f.read()
-            if f.newlines:  # .newlines may be None, str, or tuple
-                if isinstance(f.newlines, str):
-                    newline = f.newlines
-                else:
-                    newline = f.newlines[0]
-        text_before, text_after = cut_at_line(
-            changelog_text, scriv.config.insert_marker
-        )
-    else:
-        text_before = ""
-        text_after = ""
+    changelog = scriv.changelog()
+    changelog.read()
 
-    format_tools = get_format_tools(scriv.config.format, scriv.config)
-    title_data = {
-        "date": datetime.datetime.now(),
-        "version": version or scriv.config.version,
-    }
-    new_title = jinja2.Template(scriv.config.entry_title_template).render(
-        config=scriv.config, **title_data
-    )
-    if new_title.strip():
-        new_header = format_tools.format_header(new_title)
-    else:
-        new_header = ""
-    new_text = format_tools.format_sections(sections)
-    with changelog.open("w", newline=newline or None) as f:
-        f.write(text_before + new_header + new_text + text_after)
+    new_header = changelog.entry_header(version=version)
+    new_text = changelog.entry_text(scriv.combine_fragments(frags))
+    changelog.write(new_header, new_text)
 
     if edit:
-        git_edit(changelog)
+        git_edit(changelog.path)
 
     if add:
-        git_add(changelog)
+        git_add(changelog.path)
 
     if not keep:
         for frag in frags:

src/scriv/scriv.py

@@ -14,7 +14,7 @@
 from .config import Config
 from .format import SectionDict, get_format_tools
 from .gitinfo import current_branch_name, user_nick
-from .util import order_dict
+from .util import cut_at_line, order_dict
 
 
 @attr.s
@@ -40,6 +40,58 @@ def read(self) -> None:
         self.content = self.path.read_text()
 
 
+@attr.s
+class Changelog:
+    """A changelog file."""
+
+    path = attr.ib(type=Path)
+    config = attr.ib(type=Config)
+    newline = attr.ib(type=str, default="")
+    text_before = attr.ib(type=str, default="")
+    text_after = attr.ib(type=str, default="")
+
+    def read(self) -> None:
+        """Read the changelog if it exists."""
+        if self.path.exists():
+            with self.path.open("r") as f:
+                changelog_text = f.read()
+                if f.newlines:  # .newlines may be None, str, or tuple
+                    if isinstance(f.newlines, str):
+                        self.newline = f.newlines
+                    else:
+                        self.newline = f.newlines[0]
+            self.text_before, self.text_after = cut_at_line(
+                changelog_text, self.config.insert_marker
+            )
+
+    def entry_header(self, date=None, version=None) -> str:
+        """Format the header for a new entry."""
+        format_tools = get_format_tools(self.config.format, self.config)
+        title_data = {
+            "date": date or datetime.datetime.now(),
+            "version": version or self.config.version,
+        }
+        new_title = jinja2.Template(self.config.entry_title_template).render(
+            config=self.config, **title_data
+        )
+        if new_title.strip():
+            new_header = format_tools.format_header(new_title)
+        else:
+            new_header = ""
+        return new_header
+
+    def entry_text(self, sections: SectionDict) -> str:
+        """Format the text of a new entry."""
+        format_tools = get_format_tools(self.config.format, self.config)
+        new_text = format_tools.format_sections(sections)
+        return new_text
+
+    def write(self, header: str, text: str) -> None:
+        """Write the changelog, with a new entry."""
+        with self.path.open("w", newline=self.newline or None) as f:
+            f.write(self.text_before + header + text + self.text_after)
+
+
 class Scriv:
     """Public API to the scriv application."""
 
@@ -86,6 +138,13 @@ def combine_fragments(self, fragments: Iterable[Fragment]) -> SectionDict:
         sections = order_dict(sections, [None] + self.config.categories)
         return sections
 
+    def changelog(self) -> Changelog:
+        """Get the Changelog object."""
+        return Changelog(
+            path=Path(self.config.output_file),
+            config=self.config,
+        )
+
 
 def new_fragment_path(config: Config) -> Path:
     """