From a91309678c123f2cb0daec6038c9bbff3bf49eef Mon Sep 17 00:00:00 2001
From: Chris Berkhout <chrisberkhout@gmail.com>
Date: Thu, 27 May 2021 13:32:48 +0200
Subject: [PATCH] Add abstract base classes for sources and outputs.

---
 src/pricehist/outputs/baseoutput.py |  7 ++++++
 src/pricehist/outputs/beancount.py  |  4 +++-
 src/pricehist/outputs/csv.py        |  4 +++-
 src/pricehist/outputs/gnucashsql.py |  4 +++-
 src/pricehist/outputs/ledger.py     |  4 +++-
 src/pricehist/sources/basesource.py | 34 +++++++++++++++++++++++++++++
 src/pricehist/sources/coindesk.py   |  4 +++-
 7 files changed, 56 insertions(+), 5 deletions(-)
 create mode 100644 src/pricehist/outputs/baseoutput.py
 create mode 100644 src/pricehist/sources/basesource.py

diff --git a/src/pricehist/outputs/baseoutput.py b/src/pricehist/outputs/baseoutput.py
new file mode 100644
index 0000000..33cb195
--- /dev/null
+++ b/src/pricehist/outputs/baseoutput.py
@@ -0,0 +1,7 @@
+from abc import ABC, abstractmethod
+
+
+class BaseOutput(ABC):
+    @abstractmethod
+    def format(self) -> str:
+        pass
diff --git a/src/pricehist/outputs/beancount.py b/src/pricehist/outputs/beancount.py
index e378a4f..2fbcf45 100644
--- a/src/pricehist/outputs/beancount.py
+++ b/src/pricehist/outputs/beancount.py
@@ -1,7 +1,9 @@
 from pricehist.format import Format
 
+from .baseoutput import BaseOutput
 
-class Beancount:
+
+class Beancount(BaseOutput):
     def format(self, series, source=None, fmt=Format()):
         lines = []
         for price in series.prices:
diff --git a/src/pricehist/outputs/csv.py b/src/pricehist/outputs/csv.py
index 5f27615..272bd8e 100644
--- a/src/pricehist/outputs/csv.py
+++ b/src/pricehist/outputs/csv.py
@@ -1,7 +1,9 @@
 from pricehist.format import Format
 
+from .baseoutput import BaseOutput
 
-class CSV:
+
+class CSV(BaseOutput):
     def format(self, series, source=None, fmt=Format()):
         lines = ["date,base,quote,amount,source,type"]
         for price in series.prices:
diff --git a/src/pricehist/outputs/gnucashsql.py b/src/pricehist/outputs/gnucashsql.py
index 9b3439b..f4f5410 100644
--- a/src/pricehist/outputs/gnucashsql.py
+++ b/src/pricehist/outputs/gnucashsql.py
@@ -5,8 +5,10 @@ from importlib.resources import read_text
 from pricehist import __version__
 from pricehist.format import Format
 
+from .baseoutput import BaseOutput
 
-class GnuCashSQL:
+
+class GnuCashSQL(BaseOutput):
     def format(self, series, source=None, fmt=Format()):
         src = f"pricehist:{source.id()}"
 
diff --git a/src/pricehist/outputs/ledger.py b/src/pricehist/outputs/ledger.py
index b41fd2a..4301b87 100644
--- a/src/pricehist/outputs/ledger.py
+++ b/src/pricehist/outputs/ledger.py
@@ -1,7 +1,9 @@
 from pricehist.format import Format
 
+from .baseoutput import BaseOutput
 
-class Ledger:
+
+class Ledger(BaseOutput):
     def format(self, series, source=None, fmt=Format()):
         lines = []
         for price in series.prices:
diff --git a/src/pricehist/sources/basesource.py b/src/pricehist/sources/basesource.py
new file mode 100644
index 0000000..88394c0
--- /dev/null
+++ b/src/pricehist/sources/basesource.py
@@ -0,0 +1,34 @@
+from abc import ABC, abstractmethod
+
+from pricehist.series import Series
+
+
+class BaseSource(ABC):
+    @abstractmethod
+    def id(self) -> str:
+        pass
+
+    @abstractmethod
+    def name(self) -> str:
+        pass
+
+    def description(self) -> str:
+        pass
+
+    def source_url(self) -> str:
+        pass
+
+    def start(self) -> str:
+        pass
+
+    def types(self) -> list[str]:
+        pass
+
+    def notes(self) -> str:
+        pass
+
+    def symbols(self) -> list[str]:
+        pass
+
+    def fetch(self, series: Series) -> Series:
+        pass
diff --git a/src/pricehist/sources/coindesk.py b/src/pricehist/sources/coindesk.py
index e5b8a1e..40972f1 100644
--- a/src/pricehist/sources/coindesk.py
+++ b/src/pricehist/sources/coindesk.py
@@ -6,8 +6,10 @@ import requests
 
 from pricehist.price import Price
 
+from .basesource import BaseSource
 
-class CoinDesk:
+
+class CoinDesk(BaseSource):
     def id(self):
         return "coindesk"