diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..dc0aa7f
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,20 @@
+[project]
+name = "ya-changelog"
+description = "Yet another changelog CLI tool."
+authors = ["Andrew Cassidy"]
+license = "AGPL"
+readme = "README.md"
+python = "^3.8"
+homepage = "https://github.com/drewcassidy/yet-another-changelog"
+repository = "https://github.com/drewcassidy/yet-another-changelog"
+
+keywords = ["changelog", "commandline"]
+
+dependencies = ["Click", "GitPython"]
+
+[build-system]
+requires = [
+    "setuptools >= 35.0.2",
+    "setuptools_scm >= 2.0.0"
+]
+build-backend = "setuptools.build_meta"
\ No newline at end of file
diff --git a/ya_changelog/__init__.py b/ya_changelog/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/ya_changelog/changelog.py b/ya_changelog/changelog.py
new file mode 100644
index 0000000..2c5ecbd
--- /dev/null
+++ b/ya_changelog/changelog.py
@@ -0,0 +1,137 @@
+import datetime
+import os
+import re
+import string
+from typing import List, Tuple, Optional
+
+bullets = '+-*'
+brackets = '[]'
+
+
+def _strip_link(token):
+    if link_literal := re.fullmatch(r'\[(.*?)]\((.*?)\)', token):
+        # in the form [name](link)
+        return link_literal[1], link_literal[2], None
+
+    if link_id := re.fullmatch(r'\[(.*?)]\[(.*?)]', token):
+        # in the form [name][id] where id is hopefully linked somewhere else in the document
+        return link_id[1], None, link_id[2].lower()
+
+    return token, None, None
+
+
+class VersionEntry:
+    def __init__(self):
+        self.sections = {'': []}
+        self.name: str = ''
+        self.date: Optional[datetime.date] = None
+        self.tags: List[str] = []
+        self.link: str = ''
+
+    def __str__(self) -> str:
+        if self.name.lower() == 'unreleased':
+            return f'## {self.name}'
+
+        date_str = self.date.isoformat() if self.date else 'UNKNOWN'
+        line = f'## {self.name} - {date_str}'
+        for tag in self.tags:
+            line += ' [' + tag.upper() + ']'
+
+        return line
+
+
+class Changelog:
+    def __init__(self, path: os.PathLike):
+        self.path = path
+        self.header = ''
+        self.versions = []
+        self.links = {}
+
+        with open(path, 'r') as fp:
+            # Read file
+            line = fp.readline()
+            while line and not line.startswith('##'):
+                self.header += line
+                line = fp.readline()
+
+            version = None
+            section = ''
+            last_line = ''
+
+            while line:
+                if line.isspace():
+                    # skip empty lines
+                    pass
+                elif line.startswith('## '):
+                    # line is a version header
+                    version = VersionEntry()
+                    section = ''
+                    split = line.removeprefix('##').strip().split()
+
+                    version.name, version.link, version.link_id = _strip_link(split[0])
+
+                    if len(split) > 1:
+                        if split[1] == '-':
+                            split.remove('-')
+
+                        try:
+                            version.date = datetime.date.fromisoformat(split[1].strip(string.punctuation))
+                        except ValueError:
+                            version.date = None
+
+                        version.tags = [s.strip(brackets) for s in split[2:]]
+                    self.versions.append(version)
+
+                elif line.startswith('### '):
+                    # line is a version section header
+                    section = line.removeprefix('###').strip().title()
+                    if section not in version.sections.keys():
+                        version.sections[section] = []
+
+                else:
+                    # line is an entry
+                    if match := re.fullmatch(r'\[(.*)]:\s*(.*)\n', line):
+                        # this is a link, so a it to the link table
+                        self.links[match[1].lower()] = match[2]
+                    elif line[0] in bullets or last_line.isspace():
+                        # bullet point or new paragraph
+                        # bullet points are preserved since some people like to use '+', '-' or '*' for different things
+                        version.sections[section].append(line.strip())
+                    else:
+                        # not a bullet point, and no whitespace on last line, so append to the last entry
+                        version.sections[section][-1] += '\n' + line.strip()
+
+                last_line = line
+                line = fp.readline()
+
+            for version in self.versions:
+                # handle links
+                if match := re.fullmatch(r'\[(.*)]', version.name):
+                    # ref-matched link
+                    link_id = match[1].lower()
+                    if link_id in self.links:
+                        version.link = self.links.pop(link_id)
+                        version.link_id = None
+                        version.name = match[1]
+
+                elif version.link_id in self.links:
+                    # id-matched link
+                    version.link = self.links.pop(version.link_id)
+
+
+def read_version_header(line: str) -> Tuple[str, datetime.date, List[str]]:
+    split = line.removeprefix('##').strip().split()
+    name = split[0]
+    date = datetime.date.fromisoformat(split[2]) if len(split) > 2 else None
+    tags = [s.removeprefix('[').removesuffix(']') for s in split[3:]]
+
+    return name, date, tags
+
+
+def write_version_header(name: str, date: datetime.date, tags=None) -> str:
+    line = f'## {name} - {date.isoformat()}'
+    if tags:
+        for tag in tags:
+            line += ' [' + tag.upper() + ']'
+
+    return line