Create first working version

evering/__main__.py

@@ -1,48 +1,90 @@
 import argparse
-from pathlib import Path
-from typing import Union
 import logging
+from pathlib import Path
+from typing import Any
+from .config import *
+from .known_files import *
+from .process import *
+from .util import *
+from .explore import *
+from .prompt import *
 
-from .colors import *
+#logging.basicConfig(level=logging.DEBUG, style="{", format="{levelname:>7}: {message}")
-
+logging.basicConfig(level=logging.INFO, style="{", format="{levelname:>7}: {message}")
-logging.basicConfig(level=logging.DEBUG, style="{", format="{levelname:>7}: {message}")
 logger = logging.getLogger(__name__)
 
+HEADER_FILE_SUFFIX = ".evering-header"
+
+"""
+(error) -> CatastrophicError
+(warning) -> log message
+(skip/abort) -> LessCatastrophicError
+
+- Load config
+  - no readable config file found (error)
+  - config file can't be found (error)
+  - config file can't be opened (error)
+  - config file contains invalid syntax (error)
+
+- Load known files
+  - known_files can't be read (error)
+  - known_files contains invalid syntax (error)
+  - known_files contains invalid data (error)
 
 
+- Locate config files + header files
+  - missing permissions to view folders (warning)
+  - header file but no corresponding file (warning)
 
-def command_test_func(args):
+- Process files
-    logger.debug(styled("Debug", BLUE.fg, BOLD))
-    logger.info(styled("Info", GREEN.fg, BOLD))
-    logger.warning(styled("Warning", YELLOW.fg, BOLD))
-    logger.error(styled("Error", RED.fg, BOLD))
-    logger.info(styled("Test", BRIGHT_BLACK.fg, BOLD))
 
 
+Processing files
+================
 
+Header problems:
+- header file can't be read (skip/abort)
+- invalid header syntax (skip/abort)
 
+Config file problems:
+- file can't be read (skip/abort)
+- file contains no lines (warning)
+- invalid config file syntax (skip/abort)
+- error while compiling (skip/abort)
 
+Writing problems:
+- no targets (skip/abort)
+- can't write/copy to target (warning)
+- can't write to known files (error)
+"""
 
+def run(args: Any) -> None:
+    config = Config.load_config_file(args.config_file and Path(args.config_file) or None)
+    known_files = KnownFiles(config.known_files)
 
+    processor = Processor(config, known_files)
+    config_files = find_config_files(config.config_dir)
 
+    for file_info in config_files:
+        try:
+            processor.process_file(file_info.path, file_info.header)
+        except LessCatastrophicError as e:
+            logger.error(e)
 
+            if prompt_choice("[C]ontinue to the next file or [A]bort the program?", "Ca") == "a":
+                raise CatastrophicError("Aborted")
 
-
+def main() -> None:
-
-def main():
     parser = argparse.ArgumentParser()
     parser.add_argument("-c", "--config-file")
-    subparsers = parser.add_subparsers(title="commands")
-
-    command_test = subparsers.add_parser("test")
-    command_test.set_defaults(func=command_test_func)
-    command_test.add_argument("some_file")
 
     args = parser.parse_args()
-    if "func" in args:
+    try:
-        args.func(args)
+        run(args)
-    else:
+    except CatastrophicError as e:
-        parser.print_help()
+        logger.error(e)
+    except ConfigurationException as e:
+        logger.error(e)
 
 if __name__ == "__main__":
     main()

evering/colors.py

@@ -3,8 +3,9 @@ This module includes functions to color the console output with ANSI
 escape sequences.
 """
 
-from typing import Optional, Tuple
 from dataclasses import dataclass
+from pathlib import Path
+from typing import Optional, Tuple, Union
 
 __all__ = [
     "CSI", "ERASE_LINE",
@@ -12,6 +13,7 @@ __all__ = [
     "Color",
     "BLACK", "RED", "GREEN", "YELLOW", "BLUE", "MAGENTA", "CYAN", "WHITE", "BRIGHT_BLACK", "BRIGHT_RED", "BRIGHT_GREEN", "BRIGHT_YELLOW", "BRIGHT_BLUE", "BRIGHT_MAGENTA", "BRIGHT_CYAN", "BRIGHT_WHITE",
     "style_sequence", "styled",
+    "style_path", "style_var", "style_error", "style_warning",
 ]
 
 # ANSI escape sequences
@@ -61,3 +63,17 @@ def styled(text: str, *args: int) -> str:
         return f"{sequence}{text}{reset}"
     else:
         return text # No styling necessary
+
+def style_path(path: Union[str, Path]) -> str:
+    if isinstance(path, Path):
+        path = str(path)
+    return styled(path, BRIGHT_BLACK.fg, BOLD)
+
+def style_var(text: str) -> str:
+    return styled(repr(text), BLUE.fg)
+
+def style_error(text: str) -> str:
+    return styled(text, RED.fg, BOLD)
+
+def style_warning(text: str) -> str:
+    return styled(text, YELLOW.fg, BOLD)

evering/config.py

@@ -6,38 +6,292 @@ The result of loading a config file are the "local" variables,
 including the modules loaded via "import".
 """
 
+import logging
 from pathlib import Path
+from typing import Any, Dict, List, Optional, Tuple, Union
 
-__all__ = []
+from .colors import *
+from .util import *
+
+__all__ = [
+    "DEFAULT_LOCATIONS", "DEFAULT_CONFIG_FILE",
+    "ConfigurationException", "Config",
+]
+logger = logging.getLogger(__name__)
 
 DEFAULT_LOCATIONS = [
-    Path("~/.config/evering/config"),
+    Path("~/.config/evering/config.py"),
-    Path("~/.evering/config"),
+    Path("~/.evering/config.py"),
-    Path("~/.evering.conf"),
+    Path("~/.evering.py"),
 ]
 
-class LoadConfigException(Exception):
+DEFAULT_CONFIG_FILE = """
+known_files = "known_files"
+config_dir = "config/"
+binary = True
+statement_prefix = "#"
+expression_delimiters = ("{{", "}}")
+"""
+
+class ConfigurationException(Exception):
     pass
 
-def load_config(path: Path = None) -> Dict[str, Any]:
+class Config:
-    if path is not None:
+    @classmethod
-        return load_config_file(path)
+    def load_config_file(cls, path: Optional[Path]) -> "Config":
-    else:
+        """
-        for path in DEFAULT_LOCATIONS:
+        May raise: ConfigurationException
-            try:
+        """
-                return load_config_file(path)
-            except LoadConfigException:
-                # Try the next default location
-                # TODO print a log message
-                pass
-        else:
-            raise LoadConfigException("no config file found in any of the default locations")
 
-def load_config_file(path: Path) -> Dict[str, Any]:
+        local_vars: Dict[str, Any]
-    try:
+
-        with open(path) as f:
+        if path is None:
-            l = {}
+            # Try out all default config file locations
-            exec(f.read(), locals=l, globals={})
+            for path in DEFAULT_LOCATIONS:
-            return l
+                try:
-    except IOException as e:
+                    local_vars = cls._load_config_file(path)
-        raise LoadConfigException(str(e))
+                    break
+                except (ReadFileException, ExecuteException) as e:
+                    logger.debug(f"Could not load config from {style_path(path)}: {e}")
+            else:
+                raise ConfigurationException(style_error(
+                    "No valid config file found in any of the default locations"))
+        else:
+            # Use the path
+            try:
+                local_vars = cls._load_config_file(path)
+            except (ReadFileException, ExecuteException) as e:
+                raise ConfigurationException(
+                    style_error("Could not load config file from ") +
+                    style_path(path) + f": {e}")
+
+        return cls(local_vars)
+
+    @staticmethod
+    def _load_config_file(path: Path) -> Dict[str, Any]:
+        """
+        May raise: ReadFileException, ExecuteException
+        """
+
+        local_vars: Dict[str, Any] = {}
+        safer_exec(DEFAULT_CONFIG_FILE, local_vars)
+
+        safer_exec(read_file(path), local_vars)
+        if not "base_dir" in local_vars:
+            local_vars["base_dir"] = path.parent
+
+        logger.info(f"Loaded config from {style_path(str(path))}")
+
+        return local_vars
+
+    def __init__(self, local_vars: Dict[str, Any]) -> None:
+        """
+        May raise: ConfigurationException
+        """
+
+        self.local_vars = local_vars
+
+    def copy(self) -> "Config":
+        return Config(copy_local_variables(self.local_vars))
+
+    def _get(self, name: str, *types: type) -> Any:
+        """
+        May raise: ConfigurationException
+        """
+
+        if not name in self.local_vars:
+            raise ConfigurationException(
+                style_error(f"Expected a variable named ") +
+                style_var(name))
+
+        value = self.local_vars[name]
+
+        if types:
+            if not any(isinstance(value, t) for t in types):
+                raise ConfigurationException(
+                    style_error("Expexted variable ") + style_var(name) +
+                    style_error(" to have one of the following types:\n" +
+                                ", ".join(t.__name__ for t in types))
+                )
+
+        return value
+
+    def _get_optional(self, name: str, *types: type) -> Optional[Any]:
+        if not name in self.local_vars:
+            return None
+        else:
+            return self._get(name, *types)
+
+    def _set(self, name: str, value: Any) -> None:
+        self.local_vars[name] = value
+
+    @staticmethod
+    def _is_pathy(elem: Any) -> bool:
+        return isinstance(elem, str) or isinstance(elem, Path)
+
+    # Attributes begin here
+
+    # Locations and paths
+
+    @property
+    def base_dir(self) -> Path:
+        """
+        The path that is the base of all other relative paths.
+
+        Default: The directory the config file was loaded from.
+        """
+
+        return Path(self._get("base_dir", str, Path)).expanduser()
+
+    @base_dir.setter
+    def base_dir(self, path: Path) -> None:
+        self._set("base_dir", path)
+
+    def _interpret_path(self, path: Union[str, Path]) -> Path:
+        path = Path(path).expanduser()
+        if path.is_absolute():
+            logger.debug(style_path(path) + " is absolute, no interpreting required")
+            return path
+        else:
+            logger.debug(style_path(path) + " is relative, interpreting as " + style_path(self.base_dir / path))
+            return self.base_dir / path
+
+    @property
+    def known_files(self) -> Path:
+        """
+        The path where evering stores which files it is currently
+        managing.
+
+        Default: "known_files"
+        """
+
+        return self._interpret_path(self._get("known_files", str, Path))
+
+    @property
+    def config_dir(self) -> Path:
+        """
+        The directory containing the config files.
+
+        Default: "config/"
+        """
+
+        return self._interpret_path(self._get("config_dir", str, Path))
+
+    # Parsing and compiling behavior
+
+    @property
+    def binary(self) -> bool:
+        """
+        When interpreting a separate header file: Whether the
+        corresponding file should not be parsed and compiled, but
+        instead just copied to the targets.
+
+        Has no effect if the file has no header files.
+
+        Default: True
+        """
+
+        return self._get("binary", bool)
+
+    @property
+    def targets(self) -> List[Path]:
+        """
+        The locations the (compiled) config file should be put
+        in. Must be set for all files.
+
+        Default: not set
+        """
+
+        name = "targets"
+        target = self._get(name)
+        is_path = self._is_pathy(target)
+        is_list_of_paths = (isinstance(target, list) and
+                            all(self._is_pathy(elem) for elem in target))
+
+        if not is_path and not is_list_of_paths:
+            raise ConfigurationException(
+                style_error("Expected variable ") + style_var(name) +
+                style_error(" to be either a path or a list of paths"))
+
+        if is_path:
+            return [self._interpret_path(target)]
+        else:
+            return [self._interpret_path(elem) for elem in target]
+
+    @property
+    def statement_prefix(self) -> str:
+        """
+        This determines the prefix for statements like "# if",
+        "# elif", "# else" or "# endif". The prefix always has at
+        least length 1.
+
+        Default: "#"
+        """
+
+        name = "statement_prefix"
+        prefix = self._get(name, str)
+
+        if len(prefix) < 1:
+            raise ConfigurationException(
+                style_error("Expected variable ") + style_var(name) +
+                style_error(" to have at least length 1"))
+
+        return prefix
+
+    @property
+    def expression_delimiters(self) -> Tuple[str, str]:
+        """
+        This determines the delimiters for expressions like
+        "{{ 1 + 1 }}".
+
+        It is a tuple of the form: (<prefix>, <suffix>), where both
+        the prefix and suffix are strings of at least length 1.
+
+        Default: ("{{", "}}")
+        """
+
+        name = "expression_delimiters"
+        delimiters = self._get(name, tuple)
+
+        if len(delimiters) != 2:
+            raise ConfigurationException(
+                style_error("Expected variable ") + style_var(name) +
+                style_error(" to be a tuple of length 2"))
+
+        if len(delimiters[0]) < 1 or len(delimiters[1]) < 1:
+            raise ConfigurationException(
+                style_error("Expected both strings in variable ") +
+                style_var(name) + style_error( "to be of length >= 1"))
+
+        return delimiters
+
+    # Environment and file-specific information
+
+    @property
+    def filename(self) -> str:
+        """
+        The name of the file currently being compiled, as a string.
+
+        Only set during compilation.
+        """
+
+        return self._get("filename", str)
+
+    @filename.setter
+    def filename(self, filename: str) -> None:
+        self._set("filename", filename)
+
+    @property
+    def target(self) -> Path:
+        """
+        The location the file is currently being compiled for, as a
+        Path.
+
+        Only set during compilation.
+        """
+
+        return self._interpret_path(self._get("target", str, Path))
+
+    @target.setter
+    def target(self, path: Path) -> None:
+        self._set("target", path)

evering/explore.py

@@ -0,0 +1,69 @@
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Dict, List, Optional
+import logging
+
+from .util import *
+from .colors import *
+
+__all__ = ["FileInfo", "find_config_files"]
+logger = logging.getLogger(__name__)
+
+HEADER_FILE_SUFFIX = ".evering-header"
+
+@dataclass
+class FileInfo:
+    path: Path
+    header: Optional[Path] = None
+
+def find_config_files(config_dir: Path) -> List[FileInfo]:
+    try:
+        return explore_dir(config_dir)
+    except OSError as e:
+        raise CatastrophicError(style_error("could not access config dir ") + style_path(config_dir) + f": {e}")
+
+def explore_dir(cur_dir: Path) -> List[FileInfo]:
+    if not cur_dir.is_dir():
+        raise CatastrophicError(style_path(cur_dir) + style_error(" is not a directory"))
+
+    files: Dict[Path, FileInfo] = {}
+    header_files: List[Path] = []
+    subdirs: List[Path] = []
+
+    # 1. Sort all the files in this folder into their respective categories
+    for element in cur_dir.iterdir():
+        if element.is_dir():
+            logger.debug(f"Found subdir {style_path(element)}")
+            subdirs.append(element)
+        elif element.is_file():
+            if element.suffix == HEADER_FILE_SUFFIX:
+                logger.debug(f"Found header file {style_path(element)}")
+                header_files.append(element)
+            else:
+                logger.debug(f"Found file {style_path(element)}")
+                files[element] = FileInfo(element)
+        else:
+            logger.debug(f"{style_path(element)} is neither a dir nor a file")
+
+    # 2. Assign the header files to their respective files
+    for header_file in header_files:
+        matching_file = header_file.with_suffix("") # Remove last suffix
+        matching_file_info = files.get(matching_file)
+
+        if matching_file_info is None:
+            logger.warning(style_warning("No corresponding file for header file ") + style_path(header_file))
+        else:
+            logger.debug(f"Assigned header file {style_path(header_file)} to file {style_path(matching_file)}")
+            matching_file_info.header = header_file
+
+    # 3. Collect the resulting FileInfos
+    result = list(files.values())
+
+    # 4. And (try to) recursively descend into all folders
+    for subdir in subdirs:
+        try:
+            result.extend(explore_dir(subdir))
+        except OSError as e:
+            logger.warning(style_warning("Could not descend into folder ") + style_path(subdir) + f": {e}")
+
+    return result

evering/known_files.py

@@ -0,0 +1,79 @@
+import json
+import logging
+from pathlib import Path
+from typing import Dict, List, Set
+
+from .colors import *
+from .util import *
+
+__all__ = ["KnownFiles"]
+logger = logging.getLogger(__name__)
+
+class KnownFiles:
+    def __init__(self, path: Path) -> None:
+        self._path = path
+        self._old_known_files: Dict[Path, str] = {}
+        self._new_known_files: Dict[Path, str] = {}
+
+        try:
+            with open(self._path) as f:
+                self._old_known_files = self._read_known_files(f.read())
+        except FileNotFoundError as e:
+            logger.debug(f"File {style_path(self._path)} does not exist, "
+                         "creating a new file on the first upcoming save")
+
+    def _read_known_files(self, text: str) -> Dict[Path, str]:
+        known_files: Dict[Path, str] = {}
+        raw_known_files = json.loads(text)
+
+        if not isinstance(raw_known_files, dict):
+            raise CatastrophicError(style_error("Root level structure is not a dictionary"))
+
+        for path, file_hash in raw_known_files.items():
+            if not isinstance(path, str):
+                raise CatastrophicError(style_error(f"Path {path!r} is not a string"))
+            if not isinstance(file_hash, str):
+                raise CatastrophicError(style_error(f"Hash {hash!r} at path {path!r} is not a string"))
+
+            path = Path(path).expanduser().resolve() # normalized
+            known_files[path] = file_hash
+
+        return known_files
+
+    def update_file(self, path: Path, file_hash: str) -> None:
+        self._new_known_files[path.expanduser().resolve()] = file_hash
+
+    def save_incremental(self) -> None:
+        to_save: Dict[str, str] = {}
+        for path in self._old_known_files.keys() | self._new_known_files.keys():
+            if path in self._new_known_files:
+                to_save[str(path)] = self._new_known_files[path]
+            else:
+                to_save[str(path)] = self._old_known_files[path]
+
+        self._save(json.dumps(to_save))
+        logger.debug(f"Incremental save to {style_path(self._path)} completed")
+
+    def find_lost_files(self) -> Set[Path]:
+        return set(self._old_known_files.keys() - self._new_known_files.keys())
+
+    def save_final(self) -> None:
+        to_save: Dict[str, str] = {}
+
+        for path, file_hash in self._new_known_files.items():
+            to_save[str(path)] = file_hash
+
+        self._save(json.dumps(to_save))
+        logger.debug(f"Final save to {style_path(self._path)} completed")
+
+    def _save(self, text: str) -> None:
+        # Append a .tmp to the file name
+        path = Path(*self._path.parts[:-1], self._path.name + ".tmp")
+
+        try:
+            write_file(path, text)
+            path.replace(self._path) # Assumed to be atomic
+        except (WriteFileException, OSError) as e:
+            raise CatastrophicError(
+                style_error("Error saving known files to ") +
+                style_path(path) + f": {e}")

evering/parser.py

@@ -13,12 +13,10 @@ This parsing solution has the following structure:
 5. Evaluate the blocks recursively
 """
 
-__all__ = ["ParseException", "Parser"]
+__all__ = [
-
+    "split_header_and_rest",
-class ParseException(Exception):
+    "ParseException", "Parser",
-    @classmethod
+]
-    def on_line(cls, line: "Line", text: str) -> "ParseException":
-        return ParseException(f"Line {line.line_number}: {text}")
 
 def split_header_and_rest(text: str) -> Tuple[List[str], List[str]]:
     lines = text.splitlines()
@@ -40,20 +38,25 @@ def split_header_and_rest(text: str) -> Tuple[List[str], List[str]]:
 
     return header, rest
 
+class ParseException(Exception):
+    @classmethod
+    def on_line(cls, line: "Line", text: str) -> "ParseException":
+        return ParseException(f"Line {line.line_number}: {text}")
+
 class Parser:
     def __init__(self,
                  raw_lines: List[str],
-                 statement_initiator: str,
+                 statement_prefix: str,
-                 expression_opening_delimiter: str,
+                 expression_prefix: str,
-                 expression_closing_delimiter: str,
+                 expression_suffix: str,
     ) -> None:
         """
         May raise: ParseException
         """
         
-        self.statement_initiator = statement_initiator
+        self.statement_prefix = statement_prefix
-        self.expression_opening_delimiter = expression_opening_delimiter
+        self.expression_prefix = expression_prefix
-        self.expression_closing_delimiter = expression_closing_delimiter
+        self.expression_suffix = expression_suffix
 
         # Split up the text into lines and parse those
         lines: List[Line] = []
@@ -89,7 +92,7 @@ class Line(ABC):
             pass
 
         try:
-            return EndStatement(parser, text, line_number)
+            return EndifStatement(parser, text, line_number)
         except ParseException:
             pass
 
@@ -100,7 +103,7 @@ class Line(ABC):
         self.line_number = line_number
 
     def _parse_statement(self, text: str, statement_name: str) -> Optional[str]:
-        start = f"{self.parser.statement_initiator} {statement_name}"
+        start = f"{self.parser.statement_prefix} {statement_name}"
         text = text.strip()
         if text.startswith(start):
             return text[len(start):].strip()
@@ -108,7 +111,7 @@ class Line(ABC):
             return None
 
     def _parse_statement_noarg(self, text: str, statement_name: str) -> bool:
-        return text.strip() == f"{self.parser.statement_initiator} {statement_name}"
+        return text.strip() == f"{self.parser.statement_prefix} {statement_name}"
     
 class ActualLine(Line):
     def __init__(self, parser: Parser, text: str, line_number: int) -> None:
@@ -136,18 +139,18 @@ class ActualLine(Line):
 
         i = 0
         while i < len(text):
-            # Find opening delimiter
+            # Find expression prefix
-            od = text.find(self.parser.expression_opening_delimiter, i)
+            od = text.find(self.parser.expression_prefix, i)
             if od == -1:
                 chunks.append((text[i:], False))
                 break # We've consumed the entire string.
-            od_end = od + len(self.parser.expression_opening_delimiter)
+            od_end = od + len(self.parser.expression_prefix)
 
-            # Find closing delimiter
+            # Find expression suffix
-            cd = text.find(self.parser.expression_closing_delimiter, od_end)
+            cd = text.find(self.parser.expression_suffix, od_end)
             if cd == -1:
-                raise ParseException.on_line(self, f"No closing delimiter\n{text[:od_end]} <-- to THIS opening delimiter")
+                raise ParseException.on_line(self, f"No matching expression suffix\n{text[:od_end]} <-- to THIS expression prefix")
-            cd_end = cd + len(self.parser.expression_closing_delimiter)
+            cd_end = cd + len(self.parser.expression_suffix)
 
             # Split up into chunks
             chunks.append((text[i:od], False))
@@ -211,7 +214,7 @@ class ElseStatement(Line):
         if not self._parse_statement_noarg(text, "else"):
             raise ParseException.on_line(self, "Not an 'else' statement")
 
-class EndStatement(Line):
+class EndifStatement(Line):
     def __init__(self, parser: Parser, text: str, line_number: int) -> None:
         """
         May raise: ParseException
@@ -219,8 +222,8 @@ class EndStatement(Line):
 
         super().__init__(parser, line_number)
 
-        if not self._parse_statement_noarg(text, "end"):
+        if not self._parse_statement_noarg(text, "endif"):
-            raise ParseException.on_line(self, "Not an 'end' statement")
+            raise ParseException.on_line(self, "Not an 'endif' statement")
 
 # Block parsing
 
@@ -302,7 +305,7 @@ class IfBlock(Block):
 
         if not lines_queue:
             raise ParseException("Unexpected end of file, expected 'if' statement")
-        if not isinstance(lines_queue[-1], EndStatement):
+        if not isinstance(lines_queue[-1], EndifStatement):
             raise ParseException.on_line(lines_queue[-1], "Expected 'end' statement")
         lines_queue.pop()
         

evering/process.py

@@ -0,0 +1,119 @@
+import logging
+import shutil
+from pathlib import Path
+from typing import List, Optional
+
+from .colors import *
+from .config import *
+from .known_files import *
+from .parser import *
+from .util import *
+
+__all__ = ["Processor"]
+logger = logging.getLogger(__name__)
+
+class Processor:
+    def __init__(self, config: Config, known_files: KnownFiles) -> None:
+        self.config = config
+        self.known_files = known_files
+
+    def process_file(self, path: Path, header_path: Optional[Path] = None) -> None:
+        logger.info(f"{style_path(path)}:")
+
+        config = self.config.copy()
+        config.filename = path.name
+
+        if header_path is None:
+            self._process_file_without_header(path, config)
+        else:
+            self._process_file_with_header(path, header_path, config)
+
+    def _process_file_without_header(self, path: Path, config: Config) -> None:
+        logger.debug(f"Processing file {style_path(path)} with no header")
+
+        try:
+            text = read_file(path)
+        except ReadFileException as e:
+            raise LessCatastrophicError(
+                style_error("Could not load file ") +
+                style_path(path) + f": {e}")
+        
+        header, lines = split_header_and_rest(text)
+
+        try:
+            safer_exec("\n".join(header), config.local_vars)
+        except ExecuteException as e:
+            raise LessCatastrophicError(
+                style_error("Could not parse header of file ") +
+                style_path(path) + f": {e}")
+        
+        self._process_parseable(lines, config)
+
+    def _process_file_with_header(self, path: Path, header_path: Path, config: Config) -> None:
+        logger.debug(f"Processing file {style_path(path)} "
+                     f"with header {style_path(header_path)}")
+
+        try:
+            header_text = read_file(header_path)
+            safer_exec(header_text, config.local_vars)
+        except ReadFileException as e:
+            raise LessCatastrophicError(
+                style_error("Could not load header file ") +
+                style_path(header_path) + f": {e}")
+        except ExecuteException as e:
+            raise LessCatastrophicError(
+                style_error("Could not parse header file ") +
+                style_path(header_path) + f": {e}")
+
+        if config.binary:
+            self._process_binary(path, config)
+        else:
+            try:
+                lines = read_file(path).splitlines()
+            except ReadFileException as e:
+                raise LessCatastrophicError(
+                    style_error("Could not load file ") +
+                    style_path(path) + f": {e}")
+
+            self._process_parseable(lines, config)
+
+    def _process_binary(self, path: Path, config: Config) -> None:
+        logger.debug(f"Processing as a binary file")
+
+        for target in config.targets:
+            logger.info(f"  -> {style_path(str(target))}")
+
+            try:
+                shutil.copy(path, target)
+            except (IOError, shutil.SameFileError) as e:
+                logger.warning(style_warning("Could not copy") + f": {e}")
+
+    def _process_parseable(self, lines: List[str], config: Config) -> None:
+        for target in config.targets:
+            logger.info(f"  -> {style_path(str(target))}")
+
+            config_copy = config.copy()
+            config_copy.target = target
+
+            try:
+                parser = Parser(
+                    lines,
+                    statement_prefix=config.statement_prefix,
+                    expression_prefix=config.expression_delimiters[0],
+                    expression_suffix=config.expression_delimiters[1],
+                )
+                text = parser.evaluate(config_copy.local_vars)
+            except ParseException as e:
+                logger.warning(style_warning("Could not parse ") +
+                               style_path(target) + f": {e}")
+                continue
+            except ExecuteException as e:
+                logger.warning(style_warning("Could not compile ") +
+                               style_path(target) + f": {e}")
+                continue
+
+            try:
+                write_file(target, text)
+            except WriteFileException as e:
+                logger.warning(style_warning("Could not write to ") + style_path(str(target)) +
+                            f": {e}")

evering/prompt.py

@@ -0,0 +1,34 @@
+from typing import Optional
+
+__all__ = ["prompt_choice", "prompt_yes_no"]
+
+def prompt_choice(question: str, options: str) -> str:
+    default_option = None
+    for char in options:
+        if char.isupper():
+            default_option = char
+            break
+
+    option_string = "/".join(options)
+
+    while True:
+        result = input(f"{question} [{option_string}] ").lower()
+        if not result and default_option:
+            return default_option
+        # The set() makes it so that we're only testing individual
+        # characters, not substrings.
+        elif result in set(options.lower()):
+            return result
+        else:
+            print(f"Invalid answer, please choose one of [{option_string}].")
+
+def prompt_yes_no(question: str, default_answer: Optional[bool]) -> bool:
+    if default_answer is None:
+        options = "yn"
+    elif default_answer:
+        options = "Yn"
+    else:
+        options = "yN"
+
+    result = prompt_choice(question, options)
+    return result.lower() == "y"

evering/util.py

@@ -0,0 +1,88 @@
+import copy
+import types
+from pathlib import Path
+from typing import Any, Dict
+
+__all__ = [
+    "copy_local_variables",
+    "ExecuteException", "safer_exec", "safer_eval",
+    "ReadFileException", "read_file",
+    "WriteFileException", "write_file",
+    "CatastrophicError", "LessCatastrophicError",
+]
+
+def copy_local_variables(local: Dict[str, Any]) -> Dict[str, Any]:
+    """
+    Attempts to deep-copy a set of local variables, but keeping
+    modules at the top level alone, since they don't tend to deepcopy
+    well.
+    
+    May raise: Not sure at the moment
+    """
+    
+    local_copy = {}
+
+    for key, value in local.items():
+        if isinstance(value, types.ModuleType):
+            local_copy[key] = value
+        else:
+            local_copy[key] = copy.deepcopy(value)
+
+    return local_copy
+
+class ExecuteException(Exception):
+    pass
+ 
+def safer_exec(code: str, local_vars: Dict[str, Any]) -> None:
+    """
+    May raise: ExecuteException
+    """
+    
+    try:
+        exec(code, {}, local_vars)
+    except Exception as e:
+        raise ExecuteException(e)
+
+def safer_eval(code: str, local_vars: Dict[str, Any]) -> Any:
+    """
+    May raise: ExecuteException
+    """
+    
+    try:
+        return eval(code, {}, local_vars)
+    except Exception as e:
+        raise ExecuteException(e)
+
+class ReadFileException(Exception):
+    pass
+
+def read_file(path: Path) -> str:
+    """
+    May raise: ReadFileException
+    """
+    
+    try:
+        with open(path.expanduser()) as f:
+            return f.read()
+    except OSError as e:
+        raise ReadFileException(e)
+
+class WriteFileException(Exception):
+    pass
+
+def write_file(path: Path, text: str) -> None:
+    """
+    May raise: WriteFileException
+    """
+
+    try:
+        with open(path.expanduser(), "w") as f:
+            f.write(text)
+    except OSError as e:
+        raise WriteFileException(e)
+
+class CatastrophicError(Exception):
+    pass
+
+class LessCatastrophicError(Exception):
+    pass