# Copyright 1999 by Jeffrey Chang.  All rights reserved.
#
# This file is part of the Biopython distribution and governed by your
# choice of the "Biopython License Agreement" or the "BSD 3-Clause License".
# Please see the LICENSE file that should have been included as part of this
# package.

"""Code to support writing parsers (DEPRECATED).

Classes:
 - AbstractParser         Base class for parsers.
 - AbstractConsumer       Base class of all Consumers.
 - TaggingConsumer        Consumer that tags output with its event.  For debugging

Functions:
 - safe_readline          Read a line from a handle, with check for EOF.
 - safe_peekline          Peek at next line, with check for EOF.
 - read_and_call          Read a line from a handle and pass it to a method.
 - read_and_call_while    Read many lines, as long as a condition is met.
 - read_and_call_until    Read many lines, until a condition is met.
 - attempt_read_and_call  Like read_and_call, but forgiving of errors.
 - is_blank_line          Test whether a line is blank.

"""

import sys
from Bio._py3k import StringIO


class AbstractParser(object):
    """Base class for other parsers."""

    def parse(self, handle):
        raise NotImplementedError("Please implement in a derived class")

    def parse_str(self, string):
        return self.parse(StringIO(string))

    def parse_file(self, filename):
        with open(filename) as h:
            retval = self.parse(h)
        return retval


class AbstractConsumer(object):
    """Base class for other Consumers.

    Derive Consumers from this class and implement appropriate
    methods for each event that you want to receive.

    """

    def _unhandled_section(self):
        pass

    def _unhandled(self, data):
        pass

    def __getattr__(self, attr):
        if attr[:6] == 'start_' or attr[:4] == 'end_':
            method = self._unhandled_section
        else:
            method = self._unhandled
        return method


class TaggingConsumer(AbstractConsumer):
    """Debugging consumer which tags data with the event and logs it.

    This is a Consumer that tags the data stream with the event and
    prints it to a handle.  Useful for debugging.

    """

    def __init__(self, handle=None, colwidth=15, maxwidth=80):
        """Initialize.

        Arguments:
         - handle to log to, defaults to `sys.stdout`
         - colwidth for logging to the handle
         - maxwidth for truncation when logging

        """
        # I can't assign sys.stdout to handle in the argument list.
        # If I do that, handle will be assigned the value of sys.stdout
        # the first time this function is called.  This will fail if
        # the user has assigned sys.stdout to some other file, which may
        # be closed or invalid at a later time.
        if handle is None:
            handle = sys.stdout
        self._handle = handle
        self._colwidth = colwidth
        self._maxwidth = maxwidth

    def unhandled_section(self):
        self._print_name('unhandled_section')

    def unhandled(self, data):
        self._print_name('unhandled', data)

    def _print_name(self, name, data=None):
        if data is None:
            # Write the name of a section.
            self._handle.write("%s %s\n" % ("*" * self._colwidth, name))
        else:
            # Write the tag and line.
            self._handle.write("%-*s: %s\n" % (
                self._colwidth, name[:self._colwidth],
                data[:self._maxwidth - self._colwidth - 2].rstrip()))

    def __getattr__(self, attr):
        if attr[:6] == 'start_' or attr[:4] == 'end_':
            method = lambda a=attr, s=self: s._print_name(a)
        else:
            method = lambda x, a=attr, s=self: s._print_name(a, x)
        return method


def read_and_call(uhandle, method, **keywds):
    """Read line and pass it to the method.

    Read a line from uhandle, check it, and pass it to the method.
    Raises a ValueError if the line does not pass the checks.

    start, end, contains, blank, and has_re specify optional conditions
    that the line must pass.  start and end specifies what the line must
    begin or end with (not counting EOL characters).  contains
    specifies a substring that must be found in the line.  If blank
    is a true value, then the line must be blank.  has_re should be
    a regular expression object with a pattern that the line must match
    somewhere.

    """
    line = safe_readline(uhandle)
    errmsg = _fails_conditions(*(line,), **keywds)
    if errmsg is not None:
        raise ValueError(errmsg)
    method(line)


def read_and_call_while(uhandle, method, **keywds):
    """Read line and pass it to the method while condition is true.

    Read a line from uhandle and pass it to the method as long as
    some condition is true.  Returns the number of lines that were read.

    See the docstring for read_and_call for a description of the parameters.

    """
    nlines = 0
    while True:
        line = safe_readline(uhandle)
        # If I've failed the condition, then stop reading the line.
        if _fails_conditions(*(line,), **keywds):
            uhandle.saveline(line)
            break
        method(line)
        nlines = nlines + 1
    return nlines


def read_and_call_until(uhandle, method, **keywds):
    """Read line and pass it to the method until condition is true.

    Read a line from uhandle and pass it to the method until
    some condition is true.  Returns the number of lines that were read.

    See the docstring for read_and_call for a description of the parameters.

    """
    nlines = 0
    while True:
        line = safe_readline(uhandle)
        # If I've met the condition, then stop reading the line.
        if not _fails_conditions(*(line,), **keywds):
            uhandle.saveline(line)
            break
        method(line)
        nlines = nlines + 1
    return nlines


def attempt_read_and_call(uhandle, method, **keywds):
    """Attempt read line and call method.

    Similar to read_and_call, but returns a boolean specifying
    whether the line has passed the checks.  Does not raise
    exceptions.

    See docs for read_and_call for a description of the function
    arguments.

    """
    line = safe_readline(uhandle)
    passed = not _fails_conditions(*(line,), **keywds)
    if passed:
        method(line)
    else:
        uhandle.saveline(line)
    return passed


def _fails_conditions(line, start=None, end=None, contains=None, blank=None,
                      has_re=None):
    if start is not None:
        if line[:len(start)] != start:
            return "Line does not start with '%s':\n%s" % (start, line)
    if end is not None:
        if line.rstrip()[-len(end):] != end:
            return "Line does not end with '%s':\n%s" % (end, line)
    if contains is not None:
        if contains not in line:
            return "Line does not contain '%s':\n%s" % (contains, line)
    if blank is not None:
        if blank:
            if not is_blank_line(line):
                return "Expected blank line, but got:\n%s" % line
        else:
            if is_blank_line(line):
                return "Expected non-blank line, but got a blank one"
    if has_re is not None:
        if has_re.search(line) is None:
            return "Line does not match regex '%s':\n%s" % (
                has_re.pattern, line)
    return None


def is_blank_line(line, allow_spaces=0):
    """Check if a line is blank.

    Return whether a line is blank.  allow_spaces specifies whether to
    allow whitespaces in a blank line.  A true value signifies that a
    line containing whitespaces as well as end-of-line characters
    should be considered blank.

    """
    if not line:
        return 1
    if allow_spaces:
        return line.rstrip() == ''
    return line[0] == '\n' or line[0] == '\r'


def safe_readline(handle):
    """Read a line, otherwise raises ValueError.

    Read a line from an UndoHandle and return it.  If there are no more
    lines to read, I will raise a ValueError.

    """
    line = handle.readline()
    if not line:
        raise ValueError("Unexpected end of stream.")
    return line


def safe_peekline(handle):
    """Peek at the next line if present, otherwise raises ValueError.

    Peek at the next line in an UndoHandle and return it.  If there are no
    more lines to peek, I will raise a ValueError.

    """
    line = handle.peekline()
    if not line:
        raise ValueError("Unexpected end of stream.")
    return line
