From 066cf17add404a313520cd794c06e3264cf971c9 Mon Sep 17 00:00:00 2001
From: Matthias Bisping <matthias.bisping@axbit.com>
Date: Mon, 6 Feb 2023 18:40:30 +0100
Subject: [PATCH] [WIP] Either refactoring

---
 .../image_extractor/extractors/parsable.py    | 32 +++++++++++--------
 image_prediction/utils/generic.py             |  9 ++++++
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/image_prediction/image_extractor/extractors/parsable.py b/image_prediction/image_extractor/extractors/parsable.py
index 39271c9..8e80390 100644
--- a/image_prediction/image_extractor/extractors/parsable.py
+++ b/image_prediction/image_extractor/extractors/parsable.py
@@ -8,7 +8,7 @@ from typing import List, Union
 import fitz
 import numpy as np
 from PIL import Image
-from funcy import merge, compose, rcompose, keep, lfilter, none
+from funcy import merge, compose, rcompose, keep
 from pymonad.either import Right, Left, Either
 from pymonad.tools import curry, identity
 
@@ -19,7 +19,7 @@ from image_prediction.info import Info
 from image_prediction.stitching.stitching import stitch_pairs
 from image_prediction.stitching.utils import validate_box
 from image_prediction.utils import get_logger
-from image_prediction.utils.generic import bottom
+from image_prediction.utils.generic import bottom, left, right
 
 logger = get_logger()
 
@@ -50,7 +50,7 @@ class ParsablePDFImageExtractor(ImageExtractor):
         metadata = extract_valid_metadata(self.doc, page)
 
         maybe_image_metadata_pairs = map(partial(metadatum_to_image_metadata_pair, self.doc), metadata)
-        image_metadata_pairs = keep(right, maybe_image_metadata_pairs)
+        image_metadata_pairs = keep(take_right, maybe_image_metadata_pairs)
         clear_caches()
 
         image_metadata_pairs = stitch_pairs(list(image_metadata_pairs), tolerance=self.tolerance)
@@ -58,10 +58,14 @@ class ParsablePDFImageExtractor(ImageExtractor):
         yield from image_metadata_pairs
 
 
-def right(pair: Either):
+def take_right(pair: Either):
     if pair.is_right():
         return pair.either(bottom, identity)
-    logger.warning(f"Skipping bad image. {pair.either(identity, bottom)}")
+    logger.warning(f"Skipping bad image. {pair.either(format_context, bottom)}")
+
+
+def format_context(context):
+    return f"Reason: {context['reason']}. Metadata: {EnumFormatter()(context['metadata'])}"
 
 
 def extract_pages(doc, page_range):
@@ -127,14 +131,16 @@ def xref_to_maybe_image(doc, xref) -> Either:
 
 
 def make_maybe_image_metadata_pair(image: Either, metadata: Either):
-    # haskell.org/tutorial/monads.html
-    # (>>)             :: m a -> m b -> m b
-    either = Right(make_image_metadata_pair).amap(image).amap(metadata)
-    return (
-        Left({"reason": either.either(identity, bottom), "metadata": EnumFormatter()(metadata.value)})
-        if either.is_left()
-        else either
-    )
+    """
+    Reference:
+        haskell.org/tutorial/monads.html
+        (>>) :: m a -> m b -> m b
+    """
+
+    def context(value):
+        return {"reason": value, "metadata": metadata.either(bottom, identity)}
+
+    return Right(make_image_metadata_pair).amap(image).amap(metadata).either(left(context), right(identity))
 
 
 @curry(2)
diff --git a/image_prediction/utils/generic.py b/image_prediction/utils/generic.py
index ffe835e..39f75cf 100644
--- a/image_prediction/utils/generic.py
+++ b/image_prediction/utils/generic.py
@@ -1,6 +1,7 @@
 from itertools import starmap
 
 from funcy import iterate, first, curry, map
+from pymonad.either import Left, Right
 
 
 def until(cond, func, *args, **kwargs):
@@ -17,3 +18,11 @@ def starlift(fn):
 
 def bottom(*args, **kwargs):
     return None
+
+
+def left(fn):
+    return lambda x: Left(fn(x))
+
+
+def right(fn):
+    return lambda x: Right(fn(x))