1 files changed, 143 insertions, 0 deletions
diff --git a/text_recognizer/data/mappings.py b/text_recognizer/data/mappings.py
new file mode 100644
index 0000000..cfa0ec7
--- /dev/null
+++ b/text_recognizer/data/mappings.py
@@ -0,0 +1,143 @@
+"""Mapping to and from word pieces."""
+from abc import ABC, abstractmethod
+from pathlib import Path
+from typing import List, Optional, Union, Sequence
+
+from loguru import logger
+import torch
+from torch import Tensor
+
+from text_recognizer.data.emnist import emnist_mapping
+from text_recognizer.datasets.iam_preprocessor import Preprocessor
+
+
+class AbstractMapping(ABC):
+    @abstractmethod
+    def get_token(self, *args, **kwargs) -> str:
+        ...
+
+    @abstractmethod
+    def get_index(self, *args, **kwargs) -> Tensor:
+        ...
+
+    @abstractmethod
+    def get_text(self, *args, **kwargs) -> str:
+        ...
+
+    @abstractmethod
+    def get_indices(self, *args, **kwargs) -> Tensor:
+        ...
+
+
+class EmnistMapping(AbstractMapping):
+    def __init__(self, extra_symbols: Optional[Sequence[str]]) -> None:
+        self.mapping, self.inverse_mapping, self.input_size = emnist_mapping(
+            extra_symbols
+        )
+
+    def get_token(self, index: Union[int, Tensor]) -> str:
+        if (index := int(index)) in self.mapping:
+            return self.mapping[index]
+        raise KeyError(f"Index ({index}) not in mapping.")
+
+    def get_index(self, token: str) -> Tensor:
+        if token in self.inverse_mapping:
+            return Tensor(self.inverse_mapping[token])
+        raise KeyError(f"Token ({token}) not found in inverse mapping.")
+
+    def get_text(self, indices: Union[List[int], Tensor]) -> str:
+        if isinstance(indices, Tensor):
+            indices = indices.tolist()
+        return "".join([self.mapping[index] for index in indices])
+
+    def get_indices(self, text: str) -> Tensor:
+        return Tensor([self.inverse_mapping[token] for token in text])
+
+
+class WordPieceMapping(EmnistMapping):
+    def __init__(
+        self,
+        num_features: int,
+        tokens: str,
+        lexicon: str,
+        data_dir: Optional[Union[str, Path]] = None,
+        use_words: bool = False,
+        prepend_wordsep: bool = False,
+        special_tokens: Sequence[str] = ("<s>", "<e>", "<p>"),
+        extra_symbols: Optional[Sequence[str]] = None,
+    ) -> None:
+        super().__init__(extra_symbols)
+        self.wordpiece_processor = self._configure_wordpiece_processor(
+            num_features,
+            tokens,
+            lexicon,
+            data_dir,
+            use_words,
+            prepend_wordsep,
+            special_tokens,
+            extra_symbols,
+        )
+
+    def _configure_wordpiece_processor(
+        self,
+        num_features: int,
+        tokens: str,
+        lexicon: str,
+        data_dir: Optional[Union[str, Path]],
+        use_words: bool,
+        prepend_wordsep: bool,
+        special_tokens: Optional[Sequence[str]],
+        extra_symbols: Optional[Sequence[str]],
+    ) -> Preprocessor:
+        data_dir = (
+            (Path(__file__).resolve().parents[2] / "data" / "raw" / "iam" / "iamdb")
+            if data_dir is None
+            else Path(data_dir)
+        )
+
+        logger.debug(f"Using data dir: {data_dir}")
+        if not data_dir.exists():
+            raise RuntimeError(f"Could not locate iamdb directory at {data_dir}")
+
+        processed_path = (
+            Path(__file__).resolve().parents[2] / "data" / "processed" / "iam_lines"
+        )
+
+        tokens_path = processed_path / tokens
+        lexicon_path = processed_path / lexicon
+
+        if extra_symbols is not None:
+            special_tokens += extra_symbols
+
+        return Preprocessor(
+            data_dir,
+            num_features,
+            tokens_path,
+            lexicon_path,
+            use_words,
+            prepend_wordsep,
+            special_tokens,
+        )
+
+    def get_token(self, index: Union[int, Tensor]) -> str:
+        if (index := int(index)) <= self.wordpiece_processor.num_tokens:
+            return self.wordpiece_processor.tokens[index]
+        raise KeyError(f"Index ({index}) not in mapping.")
+
+    def get_index(self, token: str) -> Tensor:
+        if token in self.wordpiece_processor.tokens:
+            return torch.LongTensor(self.wordpiece_processor.tokens_to_index[token])
+        raise KeyError(f"Token ({token}) not found in inverse mapping.")
+
+    def get_text(self, indices: Union[List[int], Tensor]) -> str:
+        if isinstance(indices, Tensor):
+            indices = indices.tolist()
+        return self.wordpiece_processor.to_text(indices)
+
+    def get_indices(self, text: str) -> Tensor:
+        return self.wordpiece_processor.to_index(text)
+
+    def emnist_to_wordpiece_indices(self, x: Tensor) -> Tensor:
+        text = self.mapping.get_text(x)
+        text = text.lower().replace(" ", "▁")
+        return torch.LongTensor(self.wordpiece_processor.to_index(text))