diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c18dd8d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+__pycache__/
diff --git a/bookeeper/__main__.py b/bookeeper/__main__.py
new file mode 100644
index 0000000..9ef4a81
--- /dev/null
+++ b/bookeeper/__main__.py
@@ -0,0 +1,75 @@
+import os
+import sqlite3
+import sys
+
+from . import args
+from . import calc
+from . import db
+from . import parser
+from . import util
+
+
+try:
+  try:  # parsing args
+    params = args.parse(sys.argv[1:])
+  except Exception as e:
+    args.print_help()
+    raise Exception("failure while parsing args", e)
+
+  try:  # initializing DB
+    dbconn = sqlite3.connect(params.dbpath)
+    dbcur  = dbconn.cursor()
+    db.try_init(dbcur)
+    dbcur.execute("BEGIN;")
+  except Exception as e:
+    raise Exception("failure while initializing DB", e)
+
+  if not sys.stdin.isatty():
+    try:  # insert new records
+      for tx in parser.parse(sys.stdin):
+        db.apply(dbcur, tx)
+    except Exception as e:
+      raise Exception("failure while inserting new records", e)
+
+  try:  # writing outputs
+    calc.call(
+      calc.balancesheet,
+      params.balancesheet,
+      dbcur,
+    )
+    calc.call(
+      calc.plstatement,
+      util.get_or(params.plstatement, 0),
+      dbcur,
+      begin=util.get_or(params.plstatement, 1),
+      end  =util.get_or(params.plstatement, 2),
+    )
+    calc.call(
+      calc.balancetransition,
+      params.balancetransition,
+      dbcur,
+    )
+    calc.call(
+      calc.pltransition,
+      util.get_or(params.pltransition, 0),
+      dbcur,
+      datefmt=util.get_or(params.pltransition, 1),
+    )
+  except Exception as e:
+    raise Exception("failure while calculating output", e)
+
+except Exception as e:
+  print(f"bookeeper: error: {e}", file=sys.stderr)
+  dbcur and dbcur.execute("ROLLBACK;")
+else:
+  if params.permanentize:
+    dbcur.execute("COMMIT;")
+  else:
+    dbcur.execute("ROLLBACK;")
+
+finally:
+  if dbcur:
+    dbcur.close()
+  if dbconn:
+    dbconn.commit();
+    dbconn.close()
diff --git a/bookeeper/args.py b/bookeeper/args.py
new file mode 100644
index 0000000..10571c0
--- /dev/null
+++ b/bookeeper/args.py
@@ -0,0 +1,55 @@
+import argparse
+
+_parser = argparse.ArgumentParser(
+  prog="bookeeper",
+  description="CLI app for bookkeeping",
+  epilog="developed by falsycat <me@falsy.cat>",
+)
+
+_parser.add_argument(
+  "dbpath",
+  help="path to sqlite database file",
+  nargs="?",
+  default=":memory:",
+)
+
+_parser.add_argument(
+  "-p", "--permanentize",
+  help="apply changes",
+  action="store_true",
+  dest="permanentize",
+)
+
+_parser.add_argument(
+  "-bs", "--balancesheet",
+  help="emit balancesheet",
+  action="store",
+  dest="balancesheet",
+)
+_parser.add_argument(
+  "-bt", "--balance-transition",
+  help="emit daily transition of balance",
+  action="store",
+  dest="balancetransition",
+)
+_parser.add_argument(
+  "-pl", "--pl-statement",
+  help="emit P/L statement (filepath, begin, end)",
+  action="store",
+  nargs="+",
+  dest="plstatement",
+)
+_parser.add_argument(
+  "-plt", "--pl-transition",
+  help="emit transition of P/L",
+  action="store",
+  nargs="+",
+  dest="pltransition",
+)
+
+def print_help():
+  _parser.print_help()
+
+def parse(args):
+  ret = _parser.parse_args(args)
+  return ret
diff --git a/bookeeper/calc.py b/bookeeper/calc.py
new file mode 100644
index 0000000..30ea070
--- /dev/null
+++ b/bookeeper/calc.py
@@ -0,0 +1,101 @@
+import sys
+
+def call(func, path, *args, **kwargs):
+  if path == "-":
+    func(sys.stdout, *args, **kwargs)
+  elif path is None:
+    pass
+  else:
+    with open(path, "w") as f:
+      func(f, *args, **kwargs)
+
+def balancesheet(stream, cur):
+  cur.execute("""
+    SELECT
+      entry.type,
+      entry.name,
+      SUM(journal.amount)
+    FROM journal RIGHT JOIN entry ON journal.entry=entry.id
+    WHERE entry.type in ("A","D","N")
+    GROUP BY entry.name;
+  """)
+  for row in cur:
+    print(_recover_entry_name(row[0], row[1]), row[2], file=stream, sep=",")
+
+def plstatement(stream, cur, begin=None, end=None):
+  if begin is None:
+    begin = "0000-00-00";
+  if end is None:
+    end = "9999-12-31";
+
+  cur.execute("""
+    SELECT
+      entry.type,
+      entry.name,
+      SUM(journal.amount)
+    FROM journal
+      RIGHT JOIN entry ON journal.entry=entry.id
+      RIGHT JOIN tx    ON journal.tx   =tx.id
+    WHERE
+      entry.type in ("E","R") AND tx.date BETWEEN ? AND ?
+    GROUP BY entry.name;
+  """, (begin, end))
+  for row in cur:
+    print(_recover_entry_name(row[0], row[1]), row[2], file=stream, sep=",")
+
+def balancetransition(stream, cur):
+  cur.execute("""
+    SELECT
+      date,
+      SUM(sum)
+        OVER(ORDER BY date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
+    FROM (
+      SELECT
+        tx.date AS date,
+        SUM(
+          CASE WHEN entry.type="A" THEN journal.amount ELSE -journal.amount END
+        ) AS sum
+      FROM journal
+        RIGHT JOIN entry ON journal.entry=entry.id
+        RIGHT JOIN tx    ON journal.tx   =tx.id
+      WHERE    entry.type in ("A","D","N")
+      GROUP BY tx.date
+    );
+  """)
+  for row in cur:
+    print(*row, file=stream, sep=",")
+
+def pltransition(stream, cur, datefmt=None):
+  if datefmt is None:
+    datefmt = "%Y-%m-%d"
+  cur.execute("""
+    WITH temp AS (
+        SELECT
+          STRFTIME(?, tx.date) AS period,
+          entry.type           AS type,
+          SUM(amount)          AS sum
+        FROM journal
+          RIGHT JOIN entry ON journal.entry=entry.id
+          RIGHT JOIN tx    ON journal.tx   =tx.id
+        WHERE    entry.type in ("E","R")
+        GROUP BY period, entry.type
+      )
+    SELECT
+      a.period AS period,
+      a.sum    AS expense,
+      IFNULL(b.sum, 0) AS revenue
+    FROM temp AS a LEFT JOIN temp AS b ON a.period=b.period AND b.type="R"
+    WHERE a.type="E";
+  """, [datefmt])
+  for row in cur:
+    print(*row, file=stream, sep=",")
+
+def _recover_entry_name(t: str, name: str):
+  m = {
+    "A": "asset",
+    "D": "debt",
+    "N": "net",
+    "E": "expense",
+    "R": "revenue",
+  }
+  return f"{m[t]}/{name}"
diff --git a/bookeeper/db.py b/bookeeper/db.py
new file mode 100644
index 0000000..9968e39
--- /dev/null
+++ b/bookeeper/db.py
@@ -0,0 +1,49 @@
+import sqlite3
+
+def try_init(cur):
+  cur.execute("""
+    CREATE TABLE IF NOT EXISTS entry (
+      id   INTEGER    PRIMARY KEY AUTOINCREMENT,
+      type VARCHAR(1) NOT NULL CHECK(type IN ("A","D","N","E","R")),
+      name TEXT       NOT NULL,
+    
+      UNIQUE (type, name)
+    );
+  """)
+  cur.execute("""
+    CREATE TABLE IF NOT EXISTS tx (
+      id      INTEGER PRIMARY KEY AUTOINCREMENT,
+      summary TEXT,
+      date    DATE NOT NULL,
+      time    TIME
+    );
+  """)
+  cur.execute("""
+    CREATE TABLE IF NOT EXISTS journal (
+      id     INTEGER PRIMARY KEY AUTOINCREMENT,
+      tx     INTEGER NOT NULL,
+      entry  INTEGER NOT NULL,
+      amount INTEGER NOT NULL,
+    
+      FOREIGN KEY(tx)    REFERENCES tx(id),
+      FOREIGN KEY(entry) REFERENCES entry(name)
+    );
+  """)
+
+def apply(cur, tx):
+  cur.execute("""
+    INSERT INTO tx(summary, date, time) VALUES (?, ?, ?) RETURNING id
+  """, (tx.summary, tx.date, tx.time))
+  txid = next(cur)[0]
+
+  for j in tx.journals:
+    cur.execute("""
+      INSERT INTO entry(type, name) VALUES (?, ?)
+      ON CONFLICT DO UPDATE SET id=id
+      RETURNING id
+    """, j[0:2])
+    eid = next(cur)[0]
+
+    cur.execute("""
+      INSERT INTO journal(tx, entry, amount) VALUES (?, ?, ?)
+    """, (txid, eid, j[2]))
diff --git a/bookeeper/parser.py b/bookeeper/parser.py
new file mode 100644
index 0000000..3ba25f9
--- /dev/null
+++ b/bookeeper/parser.py
@@ -0,0 +1,80 @@
+import re
+import string
+
+from dataclasses import dataclass, field
+
+_RE_DATETIME = re.compile(r"(\d{4}-\d{2}-\d{2})(?:(@\d{2}:\d{2}))?")
+
+@dataclass
+class Tx:
+  date    : str                   = ""
+  time    : str|None              = None
+  summary : str                   = ""
+  journals: list[tuple[str, int]] = field(default_factory=lambda: [])
+
+def parse(stream):
+  parts    = []
+  end      = False
+  line_num = 0
+  while not end:
+    line_num += 1
+
+    line = stream.readline()
+    end  = ("" == line)
+
+    if end or not line[0].isspace():
+      if tx := _make_tx(parts):
+        yield tx
+      parts = []
+
+    comment = line.find("#")
+    if comment >= 0:
+      line = line[0:comment]
+
+    line = line.strip()
+    if line != "":
+      parts.append((line_num, line))
+
+def _make_tx(lines: list[tuple[int, str]]) -> dict:
+  if len(lines) < 2:
+    return None
+
+  tx = Tx()
+
+  line1 = lines[0][1].split(maxsplit=1)
+  if m := re.fullmatch(_RE_DATETIME, line1[0]):
+    tx.date = m.group(1)
+    tx.time = m.group(2)
+  else:
+    raise Exception(f"invalid datetime format: '{line1[0]}' ({lines[0][1]})")
+
+  if len(line1) == 2:
+    tx.summary = line1[1]
+
+  for line in lines[1:]:
+    tokens = line[1].split()
+    if len(tokens) != 2:
+      raise Exception("invalid journal: '{line[1]}' (line[0])")
+    t, name = _parse_entry_name(tokens[0])
+    tx.journals.append((t, name, int(tokens[1])))
+  return tx
+
+def _parse_entry_name(name: str) -> tuple[str, str]:
+  tokens = name.split("/", maxsplit=1)
+  if len(tokens) != 2:
+    raise Exception(f"invalid entry name: {name}")
+
+  if "asset" == tokens[0]:
+    t = "A"
+  elif "debt" == tokens[0]:
+    t = "D"
+  elif "net" == tokens[0]:
+    t = "N"
+  elif "expense" == tokens[0]:
+    t = "E"
+  elif "revenue" == tokens[0]:
+    t = "R"
+  else:
+    raise Exception(f"invalid entry type: {tokens[0]}")
+
+  return (t, tokens[1])
diff --git a/bookeeper/util.py b/bookeeper/util.py
new file mode 100644
index 0000000..2037e4d
--- /dev/null
+++ b/bookeeper/util.py
@@ -0,0 +1,5 @@
+def get_or(a: list, idx: int, default = None):
+  try:
+    return a[idx]
+  except:
+    return default