"""Implementation of magic functions related to History.
"""
#-----------------------------------------------------------------------------
#  Copyright (c) 2012, IPython Development Team.
#
#  Distributed under the terms of the Modified BSD License.
#
#  The full license is in the file COPYING.txt, distributed with this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

# Stdlib
import os
import sys
from io import open as io_open

# Our own packages
from IPython.core.error import StdinNotImplementedError
from IPython.core.magic import Magics, magics_class, line_magic
from IPython.core.magic_arguments import (argument, magic_arguments,
                                          parse_argstring)
from IPython.testing.skipdoctest import skip_doctest
from IPython.utils import io

#-----------------------------------------------------------------------------
# Magics class implementation
#-----------------------------------------------------------------------------


_unspecified = object()


@magics_class
class HistoryMagics(Magics):

    @magic_arguments()
    @argument(
        '-n', dest='print_nums', action='store_true', default=False,
        help="""
        print line numbers for each input.
        This feature is only available if numbered prompts are in use.
        """)
    @argument(
        '-o', dest='get_output', action='store_true', default=False,
        help="also print outputs for each input.")
    @argument(
        '-p', dest='pyprompts', action='store_true', default=False,
        help="""
        print classic '>>>' python prompts before each input.
        This is useful for making documentation, and in conjunction
        with -o, for producing doctest-ready output.
        """)
    @argument(
        '-t', dest='raw', action='store_false', default=True,
        help="""
        print the 'translated' history, as IPython understands it.
        IPython filters your input and converts it all into valid Python
        source before executing it (things like magics or aliases are turned
        into function calls, for example). With this option, you'll see the
        native history instead of the user-entered version: '%%cd /' will be
        seen as 'get_ipython().run_line_magic("cd", "/")' instead of '%%cd /'.
        """)
    @argument(
        '-f', dest='filename',
        help="""
        FILENAME: instead of printing the output to the screen, redirect
        it to the given file.  The file is always overwritten, though *when
        it can*, IPython asks for confirmation first. In particular, running
        the command 'history -f FILENAME' from the IPython Notebook
        interface will replace FILENAME even if it already exists *without*
        confirmation.
        """)
    @argument(
        '-g', dest='pattern', nargs='*', default=None,
        help="""
        treat the arg as a glob pattern to search for in (full) history.
        This includes the saved history (almost all commands ever written).
        The pattern may contain '?' to match one unknown character and '*'
        to match any number of unknown characters. Use '%%hist -g' to show
        full saved history (may be very long).
        """)
    @argument(
        '-l', dest='limit', type=int, nargs='?', default=_unspecified,
        help="""
        get the last n lines from all sessions. Specify n as a single
        arg, or the default is the last 10 lines.
        """)
    @argument(
        '-u', dest='unique', action='store_true',
        help="""
        when searching history using `-g`, show only unique history.
        """)
    @argument('range', nargs='*')
    @skip_doctest
    @line_magic
    def history(self, parameter_s = ''):
        """Print input history (_i<n> variables), with most recent last.

        By default, input history is printed without line numbers so it can be
        directly pasted into an editor. Use -n to show them.

        By default, all input history from the current session is displayed.
        Ranges of history can be indicated using the syntax:
        
        ``4``
            Line 4, current session
        ``4-6``
            Lines 4-6, current session
        ``243/1-5``
            Lines 1-5, session 243
        ``~2/7``
            Line 7, session 2 before current
        ``~8/1-~6/5``
            From the first line of 8 sessions ago, to the fifth line of 6
            sessions ago.
        
        Multiple ranges can be entered, separated by spaces

        The same syntax is used by %macro, %save, %edit, %rerun

        Examples
        --------
        ::

          In [6]: %history -n 4-6
          4:a = 12
          5:print a**2
          6:%history -n 4-6

        """

        args = parse_argstring(self.history, parameter_s)

        # For brevity
        history_manager = self.shell.history_manager

        def _format_lineno(session, line):
            """Helper function to format line numbers properly."""
            if session in (0, history_manager.session_number):
                return str(line)
            return "%s/%s" % (session, line)

        # Check if output to specific file was requested.
        outfname = args.filename
        if not outfname:
            outfile = sys.stdout  # default
            # We don't want to close stdout at the end!
            close_at_end = False
        else:
            if os.path.exists(outfname):
                try:
                    ans = io.ask_yes_no("File %r exists. Overwrite?" % outfname)
                except StdinNotImplementedError:
                    ans = True
                if not ans:
                    print('Aborting.')
                    return
                print("Overwriting file.")
            outfile = io_open(outfname, 'w', encoding='utf-8')
            close_at_end = True

        print_nums = args.print_nums
        get_output = args.get_output
        pyprompts = args.pyprompts
        raw = args.raw

        pattern = None
        limit = None if args.limit is _unspecified else args.limit

        if args.pattern is not None:
            if args.pattern:
                pattern = "*" + " ".join(args.pattern) + "*"
            else:
                pattern = "*"
            hist = history_manager.search(pattern, raw=raw, output=get_output,
                                          n=limit, unique=args.unique)
            print_nums = True
        elif args.limit is not _unspecified:
            n = 10 if limit is None else limit
            hist = history_manager.get_tail(n, raw=raw, output=get_output)
        else:
            if args.range:      # Get history by ranges
                hist = history_manager.get_range_by_str(" ".join(args.range),
                                                        raw, get_output)
            else:               # Just get history for the current session
                hist = history_manager.get_range(raw=raw, output=get_output)

        # We could be displaying the entire history, so let's not try to pull
        # it into a list in memory. Anything that needs more space will just
        # misalign.
        width = 4

        for session, lineno, inline in hist:
            # Print user history with tabs expanded to 4 spaces.  The GUI
            # clients use hard tabs for easier usability in auto-indented code,
            # but we want to produce PEP-8 compliant history for safe pasting
            # into an editor.
            if get_output:
                inline, output = inline
            inline = inline.expandtabs(4).rstrip()

            multiline = "\n" in inline
            line_sep = '\n' if multiline else ' '
            if print_nums:
                print(u'%s:%s' % (_format_lineno(session, lineno).rjust(width),
                        line_sep),  file=outfile, end=u'')
            if pyprompts:
                print(u">>> ", end=u"", file=outfile)
                if multiline:
                    inline = "\n... ".join(inline.splitlines()) + "\n..."
            print(inline, file=outfile)
            if get_output and output:
                print(output, file=outfile)

        if close_at_end:
            outfile.close()

    @line_magic
    def recall(self, arg):
        r"""Repeat a command, or get command to input line for editing.

        %recall and %rep are equivalent.

        - %recall (no arguments):

        Place a string version of last computation result (stored in the
        special '_' variable) to the next input prompt. Allows you to create
        elaborate command lines without using copy-paste::

             In[1]: l = ["hei", "vaan"]
             In[2]: "".join(l)
            Out[2]: heivaan
             In[3]: %recall
             In[4]: heivaan_ <== cursor blinking

        %recall 45

        Place history line 45 on the next input prompt. Use %hist to find
        out the number.

        %recall 1-4

        Combine the specified lines into one cell, and place it on the next
        input prompt. See %history for the slice syntax.

        %recall foo+bar

        If foo+bar can be evaluated in the user namespace, the result is
        placed at the next input prompt. Otherwise, the history is searched
        for lines which contain that substring, and the most recent one is
        placed at the next input prompt.
        """
        if not arg:                 # Last output
            self.shell.set_next_input(str(self.shell.user_ns["_"]))
            return
                                    # Get history range
        histlines = self.shell.history_manager.get_range_by_str(arg)
        cmd = "\n".join(x[2] for x in histlines)
        if cmd:
            self.shell.set_next_input(cmd.rstrip())
            return

        try:                        # Variable in user namespace
            cmd = str(eval(arg, self.shell.user_ns))
        except Exception:           # Search for term in history
            histlines = self.shell.history_manager.search("*"+arg+"*")
            for h in reversed([x[2] for x in histlines]):
                if 'recall' in h or 'rep' in h:
                    continue
                self.shell.set_next_input(h.rstrip())
                return
        else:
            self.shell.set_next_input(cmd.rstrip())
        print("Couldn't evaluate or find in history:", arg)

    @line_magic
    def rerun(self, parameter_s=''):
        """Re-run previous input

        By default, you can specify ranges of input history to be repeated
        (as with %history). With no arguments, it will repeat the last line.

        Options:

          -l <n> : Repeat the last n lines of input, not including the
          current command.

          -g foo : Repeat the most recent line which contains foo
        """
        opts, args = self.parse_options(parameter_s, 'l:g:', mode='string')
        if "l" in opts:         # Last n lines
            n = int(opts['l'])
            hist = self.shell.history_manager.get_tail(n)
        elif "g" in opts:       # Search
            p = "*"+opts['g']+"*"
            hist = list(self.shell.history_manager.search(p))
            for l in reversed(hist):
                if "rerun" not in l[2]:
                    hist = [l]     # The last match which isn't a %rerun
                    break
            else:
                hist = []          # No matches except %rerun
        elif args:              # Specify history ranges
            hist = self.shell.history_manager.get_range_by_str(args)
        else:                   # Last line
            hist = self.shell.history_manager.get_tail(1)
        hist = [x[2] for x in hist]
        if not hist:
            print("No lines in history match specification")
            return
        histlines = "\n".join(hist)
        print("=== Executing: ===")
        print(histlines)
        print("=== Output: ===")
        self.shell.run_cell("\n".join(hist), store_history=False)
