# -*- encoding: utf-8 -*-
# Copyright 2020 the authors.
# This file is part of Hy, which is free software licensed under the Expat
# license. See the LICENSE.
import os
import re
import sys
import traceback
import pkgutil

from functools import reduce
from colorama import Fore
from contextlib import contextmanager
from hy import _initialize_env_var

_hy_filter_internal_errors = _initialize_env_var('HY_FILTER_INTERNAL_ERRORS',
                                                 True)
COLORED = _initialize_env_var('HY_COLORED_ERRORS', False)


class HyError(Exception):
    pass


class HyInternalError(HyError):
    """Unexpected errors occurring during compilation or parsing of Hy code.

    Errors sub-classing this are not intended to be user-facing, and will,
    hopefully, never be seen by users!
    """


class HyLanguageError(HyError):
    """Errors caused by invalid use of the Hy language.

    This, and any errors inheriting from this, are user-facing.
    """

    def __init__(self, message, expression=None, filename=None, source=None,
                 lineno=1, colno=1):
        """
        Parameters
        ----------
        message: str
            The message to display for this error.
        expression: HyObject, optional
            The Hy expression generating this error.
        filename: str, optional
            The filename for the source code generating this error.
            Expression-provided information will take precedence of this value.
        source: str, optional
            The actual source code generating this error.  Expression-provided
            information will take precedence of this value.
        lineno: int, optional
            The line number of the error.  Expression-provided information will
            take precedence of this value.
        colno: int, optional
            The column number of the error.  Expression-provided information
            will take precedence of this value.
        """
        self.msg = message
        self.compute_lineinfo(expression, filename, source, lineno, colno)

        if isinstance(self, SyntaxError):
            syntax_error_args = (self.filename, self.lineno, self.offset,
                                 self.text)
            super(HyLanguageError, self).__init__(message, syntax_error_args)
        else:
            super(HyLanguageError, self).__init__(message)

    def compute_lineinfo(self, expression, filename, source, lineno, colno):

        # NOTE: We use `SyntaxError`'s field names (i.e. `text`, `offset`,
        # `msg`) for compatibility and print-outs.
        self.text = getattr(expression, 'source', source)
        self.filename = getattr(expression, 'filename', filename)

        if self.text:
            lines = self.text.splitlines()

            self.lineno = getattr(expression, 'start_line', lineno)
            self.offset = getattr(expression, 'start_column', colno)
            end_column = getattr(expression, 'end_column',
                                 len(lines[self.lineno-1]))
            end_line = getattr(expression, 'end_line', self.lineno)

            # Trim the source down to the essentials.
            self.text = '\n'.join(lines[self.lineno-1:end_line])

            if end_column:
                if self.lineno == end_line:
                    self.arrow_offset = end_column
                else:
                    self.arrow_offset = len(self.text[0])

                self.arrow_offset -= self.offset
            else:
                self.arrow_offset = None
        else:
            # We could attempt to extract the source given a filename, but we
            # don't.
            self.lineno = lineno
            self.offset = colno
            self.arrow_offset = None

    def __str__(self):
        """Provide an exception message that includes SyntaxError-like source
        line information when available.
        """
        # Syntax errors are special and annotate the traceback (instead of what
        # we would do in the message that follows the traceback).
        if isinstance(self, SyntaxError):
            return super(HyLanguageError, self).__str__()
        # When there isn't extra source information, use the normal message.
        elif not self.text:
            return super(HyLanguageError, self).__str__()

        # Re-purpose Python's builtin syntax error formatting.
        output = traceback.format_exception_only(
            SyntaxError,
            SyntaxError(self.msg, (self.filename, self.lineno, self.offset,
                                   self.text)))

        arrow_idx, _ = next(((i, x) for i, x in enumerate(output)
                             if x.strip() == '^'),
                            (None, None))
        if arrow_idx:
            msg_idx = arrow_idx + 1
        else:
            msg_idx, _ = next((i, x) for i, x in enumerate(output)
                              if x.startswith('SyntaxError: '))

        # Get rid of erroneous error-type label.
        output[msg_idx] = re.sub('^SyntaxError: ', '', output[msg_idx])

        # Extend the text arrow, when given enough source info.
        if arrow_idx and self.arrow_offset:
            output[arrow_idx] = '{}{}^\n'.format(output[arrow_idx].rstrip('\n'),
                                                 '-' * (self.arrow_offset - 1))

        if COLORED:
            output[msg_idx:] = [Fore.YELLOW + o + Fore.RESET for o in output[msg_idx:]]
            if arrow_idx:
                output[arrow_idx] = Fore.GREEN + output[arrow_idx] + Fore.RESET
            for idx, line in enumerate(output[::msg_idx]):
                if line.strip().startswith(
                        'File "{}", line'.format(self.filename)):
                    output[idx] = Fore.RED + line + Fore.RESET

        # This resulting string will come after a "<class-name>:" prompt, so
        # put it down a line.
        output.insert(0, '\n')

        # Avoid "...expected str instance, ColoredString found"
        return reduce(lambda x, y: x + y, output)


class HyCompileError(HyInternalError):
    """Unexpected errors occurring within the compiler."""


class HyTypeError(HyLanguageError, TypeError):
    """TypeError occurring during the normal use of Hy."""


class HyNameError(HyLanguageError, NameError):
    """NameError occurring during the normal use of Hy."""


class HyRequireError(HyLanguageError):
    """Errors arising during the use of `require`

    This, and any errors inheriting from this, are user-facing.
    """


class HyMacroExpansionError(HyLanguageError):
    """Errors caused by invalid use of Hy macros.

    This, and any errors inheriting from this, are user-facing.
    """


class HyEvalError(HyLanguageError):
    """Errors occurring during code evaluation at compile-time.

    These errors distinguish unexpected errors within the compilation process
    (i.e. `HyInternalError`s) from unrelated errors in user code evaluated by
    the compiler (e.g. in `eval-and-compile`).

    This, and any errors inheriting from this, are user-facing.
    """


class HyIOError(HyInternalError, IOError):
    """ Subclass used to distinguish between IOErrors raised by Hy itself as
    opposed to Hy programs.
    """


class HySyntaxError(HyLanguageError, SyntaxError):
    """Error during the Lexing of a Hython expression."""


class HyWrapperError(HyError, TypeError):
    """Errors caused by language model object wrapping.

    These can be caused by improper user-level use of a macro, so they're
    not really "internal".  If they arise due to anything else, they're an
    internal/compiler problem, though.
    """


def _module_filter_name(module_name):
    try:
        compiler_loader = pkgutil.get_loader(module_name)
        if not compiler_loader:
            return None

        filename = compiler_loader.get_filename(module_name)
        if not filename:
            return None

        if compiler_loader.is_package(module_name):
            # Use the package directory (e.g. instead of `.../__init__.py`) so
            # that we can filter all modules in a package.
            return os.path.dirname(filename)
        else:
            # Normalize filename endings, because tracebacks will use `pyc` when
            # the loader says `py`.
            return filename.replace('.pyc', '.py')
    except Exception:
        return None


_tb_hidden_modules = {m for m in map(_module_filter_name,
                                     ['hy.compiler', 'hy.lex',
                                      'hy.cmdline', 'hy.lex.parser',
                                      'hy.importer', 'hy._compat',
                                      'hy.macros', 'hy.models',
                                      'rply'])
                      if m is not None}


def hy_exc_filter(exc_type, exc_value, exc_traceback):
    """Produce exceptions print-outs with all frames originating from the
    modules in `_tb_hidden_modules` filtered out.

    The frames are actually filtered by each module's filename and only when a
    subclass of `HyLanguageError` is emitted.

    This does not remove the frames from the actual tracebacks, so debugging
    will show everything.
    """
    # frame = (filename, line number, function name*, text)
    new_tb = []
    for frame in traceback.extract_tb(exc_traceback):
        if not (frame[0].replace('.pyc', '.py') in _tb_hidden_modules or
                os.path.dirname(frame[0]) in _tb_hidden_modules):
            new_tb += [frame]

    lines = traceback.format_list(new_tb)

    lines.insert(0, "Traceback (most recent call last):\n")

    lines.extend(traceback.format_exception_only(exc_type, exc_value))
    output = ''.join(lines)

    return output


def hy_exc_handler(exc_type, exc_value, exc_traceback):
    """A `sys.excepthook` handler that uses `hy_exc_filter` to
    remove internal Hy frames from a traceback print-out.
    """
    if os.environ.get('HY_DEBUG', False):
        return sys.__excepthook__(exc_type, exc_value, exc_traceback)

    try:
        output = hy_exc_filter(exc_type, exc_value, exc_traceback)
        sys.stderr.write(output)
        sys.stderr.flush()
    except Exception:
        sys.__excepthook__(exc_type, exc_value, exc_traceback)


@contextmanager
def filtered_hy_exceptions():
    """Temporarily apply a `sys.excepthook` that filters Hy internal frames
    from tracebacks.

    Filtering can be controlled by the variable
    `hy.errors._hy_filter_internal_errors` and environment variable
    `HY_FILTER_INTERNAL_ERRORS`.
    """
    global _hy_filter_internal_errors
    if _hy_filter_internal_errors:
        current_hook = sys.excepthook
        sys.excepthook = hy_exc_handler
        yield
        sys.excepthook = current_hook
    else:
        yield