Create separate packages for library and CLI

1 files changed, 108 insertions, 0 deletions

diff --git a/flashcards-project/src/flashcards/parser.py b/flashcards-project/src/flashcards/parser.py
new file mode 100644
index 0000000..38abdcc
--- /dev/null
+++ b/flashcards-project/src/flashcards/parser.py
@@ -0,0 +1,108 @@
+"""
+Load .fcard files into dictionaries.
+
+The parser expects .fcard files in the following format:
+
+FRONT
+This is the front of the first card.
+
+BACK
+This is the back of the first card.
+
+FRONT
+This is another card.
+
+Multiple lines on the front are allowed.
+
+BACK
+Multiple lines on the back?
+
+Also allowed.
+
+FRONT
+...
+
+The cards are represented in dictionary entries of the form:
+
+id: card.Card
+"""
+from pathlib import Path
+from enum import Enum
+from typing import TextIO, Iterator
+
+from .card import Card, getId
+
+def _getCard(front_lines: list[str], back_lines: list[str]) -> tuple[str, Card]:
+    front_text = "".join(front_lines).strip()
+    back_text = "".join(back_lines).strip()
+    card = Card(front_text, back_text)
+    id = getId(card)
+    return id, card
+
+def _getCards(f: TextIO) -> Iterator[tuple[str, Card]]:
+    class State(Enum):
+        PARSE_FRONT = 1,
+        PARSE_BACK = 2
+    
+    state = None
+    front_lines = []
+    back_lines = []
+
+    for i, line in enumerate(f):
+        match line.strip():
+            case "FRONT":
+                # Edge case: FRONT twice in a row
+                if state == State.PARSE_FRONT:
+                    raise Exception(f"Unexpected 'FRONT': {f}:{i}")
+
+                # Next card is starting, wrap up current one
+                if state == State.PARSE_BACK:
+                    yield _getCard(front_lines, back_lines)
+                    front_lines.clear()
+                    back_lines.clear()
+
+                state = State.PARSE_FRONT
+
+            case "BACK":
+                # Edge case: BACK without FRONT before it
+                if state != State.PARSE_FRONT:
+                    raise Exception(f"Unexpected 'BACK': {f}:{i}")
+
+                state = State.PARSE_BACK
+                
+            case _:
+                match state:
+                    case State.PARSE_FRONT:
+                        front_lines += line
+                    case State.PARSE_BACK:
+                        back_lines += line
+                    # Edge case: file does not start with FRONT, flush preamble
+                    case _:
+                        continue
+
+    # Edge case: file did not end with contents of BACK
+    if state == State.PARSE_FRONT:
+        raise Exception(f"Unexpected end of file")
+
+    # Edge case: file was empty
+    if state is None:
+        return
+
+    yield _getCard(front_lines, back_lines)
+
+def parseFile(path: str) -> dict[str, Card]:
+    """
+    Parse a .fcard file and return a dictionary of Card instances indexed by ID.
+    """
+    with open(path, "r") as f:
+        return {id : card for id, card in _getCards(f)}
+
+def parseFiles(paths: list[str]) -> dict[str, Card]:
+    """
+    Parse a list of .fcard files and return a dictionary of Card instances indexed by ID.
+    """
+    cards = {}
+    for p in paths:
+        cards |= parseFile(p)
+    return cards
+