"""
Basically a contains parser that is faster, because it tries to parse only
parts and if anything changes, it only reparses the changed parts.

It works with a simple diff in the beginning and will try to reuse old parser
fragments.
"""
import re
import difflib
from collections import namedtuple
import logging

from parso.utils import splitlines
from parso.python.parser import Parser, remove_last_newline
from parso.python.tree import EndMarker
from parso.tokenize import (generate_tokens, NEWLINE, TokenInfo,
                            ENDMARKER, INDENT, DEDENT)


def _get_last_line(node_or_leaf):
    last_leaf = node_or_leaf.get_last_leaf()
    if _ends_with_newline(last_leaf):
        return last_leaf.start_pos[0]
    else:
        return last_leaf.end_pos[0]


def _ends_with_newline(leaf, suffix=''):
    if leaf.type == 'error_leaf':
        typ = leaf.original_type
    else:
        typ = leaf.type

    return typ == 'newline' or suffix.endswith('\n')


def _flows_finished(pgen_grammar, stack):
    """
    if, while, for and try might not be finished, because another part might
    still be parsed.
    """
    for dfa, newstate, (symbol_number, nodes) in stack:
        if pgen_grammar.number2symbol[symbol_number] in ('if_stmt', 'while_stmt',
                                                    'for_stmt', 'try_stmt'):
            return False
    return True


def suite_or_file_input_is_valid(pgen_grammar, stack):
    if not _flows_finished(pgen_grammar, stack):
        return False

    for dfa, newstate, (symbol_number, nodes) in reversed(stack):
        if pgen_grammar.number2symbol[symbol_number] == 'suite':
            # If only newline is in the suite, the suite is not valid, yet.
            return len(nodes) > 1
    # Not reaching a suite means that we're dealing with file_input levels
    # where there's no need for a valid statement in it. It can also be empty.
    return True


def _is_flow_node(node):
    try:
        value = node.children[0].value
    except AttributeError:
        return False
    return value in ('if', 'for', 'while', 'try')


class _PositionUpdatingFinished(Exception):
    pass


def _update_positions(nodes, line_offset, last_leaf):
    for node in nodes:
        try:
            children = node.children
        except AttributeError:
            # Is a leaf
            node.line += line_offset
            if node is last_leaf:
                raise _PositionUpdatingFinished
        else:
            _update_positions(children, line_offset, last_leaf)


class DiffParser(object):
    """
    An advanced form of parsing a file faster. Unfortunately comes with huge
    side effects. It changes the given module.
    """
    def __init__(self, pgen_grammar, module):
        self._pgen_grammar = pgen_grammar
        self._module = module

    def _reset(self):
        self._copy_count = 0
        self._parser_count = 0

        self._nodes_stack = _NodesStack(self._module)

    def update(self, old_lines, new_lines):
        '''
        The algorithm works as follows:

        Equal:
            - Assure that the start is a newline, otherwise parse until we get
              one.
            - Copy from parsed_until_line + 1 to max(i2 + 1)
            - Make sure that the indentation is correct (e.g. add DEDENT)
            - Add old and change positions
        Insert:
            - Parse from parsed_until_line + 1 to min(j2 + 1), hopefully not
              much more.

        Returns the new module node.
        '''
        logging.debug('diff parser start')
        # Reset the used names cache so they get regenerated.
        self._module._used_names = None

        self._parser_lines_new = new_lines
        self._added_newline = False
        if new_lines[-1] != '':
            # The Python grammar needs a newline at the end of a file, but for
            # everything else we keep working with new_lines here.
            self._parser_lines_new = list(new_lines)
            self._parser_lines_new[-1] += '\n'
            self._parser_lines_new.append('')
            self._added_newline = True

        self._reset()

        line_length = len(new_lines)
        sm = difflib.SequenceMatcher(None, old_lines, self._parser_lines_new)
        opcodes = sm.get_opcodes()
        logging.debug('diff parser calculated')
        logging.debug('diff: line_lengths old: %s, new: %s' % (len(old_lines), line_length))

        for operation, i1, i2, j1, j2 in opcodes:
            logging.debug('diff %s old[%s:%s] new[%s:%s]',
                      operation, i1 + 1, i2, j1 + 1, j2)

            if j2 == line_length + int(self._added_newline):
                # The empty part after the last newline is not relevant.
                j2 -= 1

            if operation == 'equal':
                line_offset = j1 - i1
                self._copy_from_old_parser(line_offset, i2, j2)
            elif operation == 'replace':
                self._parse(until_line=j2)
            elif operation == 'insert':
                self._parse(until_line=j2)
            else:
                assert operation == 'delete'

        # With this action all change will finally be applied and we have a
        # changed module.
        self._nodes_stack.close()

        if self._added_newline:
            remove_last_newline(self._module)

        last_pos = self._module.end_pos[0]
        if last_pos != line_length:
            current_lines = splitlines(self._module.get_code(), keepends=True)
            diff = difflib.unified_diff(current_lines, new_lines)
            raise Exception(
                "There's an issue (%s != %s) with the diff parser. Please report:\n%s"
                % (last_pos, line_length, ''.join(diff))
            )

        logging.debug('diff parser end')
        return self._module

    def _enabled_debugging(self, old_lines, lines_new):
        if self._module.get_code() != ''.join(lines_new):
            logging.warning('parser issue:\n%s\n%s', ''.join(old_lines),
                            ''.join(lines_new))

    def _copy_from_old_parser(self, line_offset, until_line_old, until_line_new):
        copied_nodes = [None]

        last_until_line = -1
        while until_line_new > self._nodes_stack.parsed_until_line:
            parsed_until_line_old = self._nodes_stack.parsed_until_line - line_offset
            line_stmt = self._get_old_line_stmt(parsed_until_line_old + 1)
            if line_stmt is None:
                # Parse 1 line at least. We don't need more, because we just
                # want to get into a state where the old parser has statements
                # again that can be copied (e.g. not lines within parentheses).
                self._parse(self._nodes_stack.parsed_until_line + 1)
            elif not copied_nodes:
                # We have copied as much as possible (but definitely not too
                # much). Therefore we just parse the rest.
                # We might not reach the end, because there's a statement
                # that is not finished.
                self._parse(until_line_new)
            else:
                p_children = line_stmt.parent.children
                index = p_children.index(line_stmt)

                copied_nodes = self._nodes_stack.copy_nodes(
                    p_children[index:],
                    until_line_old,
                    line_offset
                )
                # Match all the nodes that are in the wanted range.
                if copied_nodes:
                    self._copy_count += 1

                    from_ = copied_nodes[0].get_start_pos_of_prefix()[0] + line_offset
                    to = self._nodes_stack.parsed_until_line

                    logging.debug('diff actually copy %s to %s', from_, to)
            # Since there are potential bugs that might loop here endlessly, we
            # just stop here.
            assert last_until_line != self._nodes_stack.parsed_until_line \
                or not copied_nodes, last_until_line
            last_until_line = self._nodes_stack.parsed_until_line

    def _get_old_line_stmt(self, old_line):
        leaf = self._module.get_leaf_for_position((old_line, 0), include_prefixes=True)

        if _ends_with_newline(leaf):
            leaf = leaf.get_next_leaf()
        if leaf.get_start_pos_of_prefix()[0] == old_line:
            node = leaf
            while node.parent.type not in ('file_input', 'suite'):
                node = node.parent
            return node
        # Must be on the same line. Otherwise we need to parse that bit.
        return None

    def _get_before_insertion_node(self):
        if self._nodes_stack.is_empty():
            return None

        line = self._nodes_stack.parsed_until_line + 1
        node = self._new_module.get_last_leaf()
        while True:
            parent = node.parent
            if parent.type in ('suite', 'file_input'):
                assert node.end_pos[0] <= line
                assert node.end_pos[1] == 0 or '\n' in self._prefix
                return node
            node = parent

    def _parse(self, until_line):
        """
        Parses at least until the given line, but might just parse more until a
        valid state is reached.
        """
        last_until_line = 0
        while until_line > self._nodes_stack.parsed_until_line:
            node = self._try_parse_part(until_line)
            nodes = self._get_children_nodes(node)
            #self._insert_nodes(nodes)

            self._nodes_stack.add_parsed_nodes(nodes)
            logging.debug(
                'parse part %s to %s (to %s in parser)',
                nodes[0].get_start_pos_of_prefix()[0],
                self._nodes_stack.parsed_until_line,
                node.end_pos[0] - 1
            )
            # Since the tokenizer sometimes has bugs, we cannot be sure that
            # this loop terminates. Therefore assert that there's always a
            # change.
            assert last_until_line != self._nodes_stack.parsed_until_line, last_until_line
            last_until_line = self._nodes_stack.parsed_until_line

    def _get_children_nodes(self, node):
        nodes = node.children
        first_element = nodes[0]
        # TODO this looks very strange...
        if first_element.type == 'error_leaf' and \
                first_element.original_type == 'indent':
            assert False, str(nodes)

        return nodes

    def _try_parse_part(self, until_line):
        """
        Sets up a normal parser that uses a spezialized tokenizer to only parse
        until a certain position (or a bit longer if the statement hasn't
        ended.
        """
        self._parser_count += 1
        # TODO speed up, shouldn't copy the whole list all the time.
        # memoryview?
        parsed_until_line = self._nodes_stack.parsed_until_line
        lines_after = self._parser_lines_new[parsed_until_line:]
        #print('parse_content', parsed_until_line, lines_after, until_line)
        tokens = self._diff_tokenize(
            lines_after,
            until_line,
            line_offset=parsed_until_line
        )
        self._active_parser = Parser(
            self._pgen_grammar,
            error_recovery=True
        )
        return self._active_parser.parse(tokens=tokens)

    def _diff_tokenize(self, lines, until_line, line_offset=0):
        is_first_token = True
        omitted_first_indent = False
        indents = []
        tokens = generate_tokens(lines, use_exact_op_types=True)
        stack = self._active_parser.pgen_parser.stack
        for typ, string, start_pos, prefix in tokens:
            start_pos = start_pos[0] + line_offset, start_pos[1]
            if typ == INDENT:
                indents.append(start_pos[1])
                if is_first_token:
                    omitted_first_indent = True
                    # We want to get rid of indents that are only here because
                    # we only parse part of the file. These indents would only
                    # get parsed as error leafs, which doesn't make any sense.
                    is_first_token = False
                    continue
            is_first_token = False

            if typ == DEDENT:
                indents.pop()
                if omitted_first_indent and not indents:
                    # We are done here, only thing that can come now is an
                    # endmarker or another dedented code block.
                    typ, string, start_pos, prefix = next(tokens)
                    if '\n' in prefix:
                        prefix = re.sub(r'(<=\n)[^\n]+$', '', prefix)
                    else:
                        prefix = ''
                    yield TokenInfo(ENDMARKER, '', (start_pos[0] + line_offset, 0), prefix)
                    break
            elif typ == NEWLINE and start_pos[0] >= until_line:
                yield TokenInfo(typ, string, start_pos, prefix)
                # Check if the parser is actually in a valid suite state.
                if suite_or_file_input_is_valid(self._pgen_grammar, stack):
                    start_pos = start_pos[0] + 1, 0
                    while len(indents) > int(omitted_first_indent):
                        indents.pop()
                        yield TokenInfo(DEDENT, '', start_pos, '')

                    yield TokenInfo(ENDMARKER, '', start_pos, '')
                    break
                else:
                    continue

            yield TokenInfo(typ, string, start_pos, prefix)


class _NodesStackNode(object):
    ChildrenGroup = namedtuple('ChildrenGroup', 'children line_offset last_line_offset_leaf')

    def __init__(self, tree_node, parent=None):
        self.tree_node = tree_node
        self.children_groups = []
        self.parent = parent

    def close(self):
        children = []
        for children_part, line_offset, last_line_offset_leaf in self.children_groups:
            if line_offset != 0:
                try:
                    _update_positions(
                        children_part, line_offset, last_line_offset_leaf)
                except _PositionUpdatingFinished:
                    pass
            children += children_part
        self.tree_node.children = children
        # Reset the parents
        for node in children:
            node.parent = self.tree_node

    def add(self, children, line_offset=0, last_line_offset_leaf=None):
        group = self.ChildrenGroup(children, line_offset, last_line_offset_leaf)
        self.children_groups.append(group)

    def get_last_line(self, suffix):
        line = 0
        if self.children_groups:
            children_group = self.children_groups[-1]
            last_leaf = children_group.children[-1].get_last_leaf()
            line = last_leaf.end_pos[0]

            # Calculate the line offsets
            offset = children_group.line_offset
            if offset:
                # In case the line_offset is not applied to this specific leaf,
                # just ignore it.
                if last_leaf.line <= children_group.last_line_offset_leaf.line:
                    line += children_group.line_offset

            # Newlines end on the next line, which means that they would cover
            # the next line. That line is not fully parsed at this point.
            if _ends_with_newline(last_leaf, suffix):
                line -= 1
        line += suffix.count('\n')
        return line


class _NodesStack(object):
    endmarker_type = 'endmarker'

    def __init__(self, module):
        # Top of stack
        self._tos = self._base_node = _NodesStackNode(module)
        self._module = module
        self._last_prefix = ''
        self.prefix = ''

    def is_empty(self):
        return not self._base_node.children

    @property
    def parsed_until_line(self):
        return self._tos.get_last_line(self.prefix)

    def _get_insertion_node(self, indentation_node):
        indentation = indentation_node.start_pos[1]

        # find insertion node
        node = self._tos
        while True:
            tree_node = node.tree_node
            if tree_node.type == 'suite':
                # A suite starts with NEWLINE, ...
                node_indentation = tree_node.children[1].start_pos[1]

                if indentation >= node_indentation:  # Not a Dedent
                    # We might be at the most outer layer: modules. We
                    # don't want to depend on the first statement
                    # having the right indentation.
                    return node

            elif tree_node.type == 'file_input':
                return node

            node = self._close_tos()

    def _close_tos(self):
        self._tos.close()
        self._tos = self._tos.parent
        return self._tos

    def add_parsed_nodes(self, tree_nodes):
        tree_nodes = self._remove_endmarker(tree_nodes)
        if not tree_nodes:
            return

        assert tree_nodes[0].type != 'newline'

        node = self._get_insertion_node(tree_nodes[0])
        assert node.tree_node.type in ('suite', 'file_input')
        node.add(tree_nodes)
        self._update_tos(tree_nodes[-1])

    def _remove_endmarker(self, tree_nodes):
        """
        Helps cleaning up the tree nodes that get inserted.
        """
        last_leaf = tree_nodes[-1].get_last_leaf()
        is_endmarker = last_leaf.type == self.endmarker_type
        self._last_prefix = ''
        if is_endmarker:
            try:
                separation = last_leaf.prefix.rindex('\n')
            except ValueError:
                pass
            else:
                # Remove the whitespace part of the prefix after a newline.
                # That is not relevant if parentheses were opened. Always parse
                # until the end of a line.
                last_leaf.prefix, self._last_prefix = \
                    last_leaf.prefix[:separation + 1], last_leaf.prefix[separation + 1:]

        first_leaf = tree_nodes[0].get_first_leaf()
        first_leaf.prefix = self.prefix + first_leaf.prefix
        self.prefix = ''

        if is_endmarker:
            self.prefix = last_leaf.prefix

            tree_nodes = tree_nodes[:-1]

        return tree_nodes

    def copy_nodes(self, tree_nodes, until_line, line_offset):
        """
        Copies tree nodes from the old parser tree.

        Returns the number of tree nodes that were copied.
        """
        tos = self._get_insertion_node(tree_nodes[0])

        new_nodes, self._tos = self._copy_nodes(tos, tree_nodes, until_line, line_offset)
        return new_nodes

    def _copy_nodes(self, tos, nodes, until_line, line_offset):
        new_nodes = []

        new_tos = tos
        for node in nodes:
            if node.type == 'endmarker':
                # Endmarkers just distort all the checks below. Remove them.
                break

            if node.start_pos[0] > until_line:
                break
            # TODO this check might take a bit of time for large files. We
            # might want to change this to do more intelligent guessing or
            # binary search.
            if _get_last_line(node) > until_line:
                # We can split up functions and classes later.
                if node.type in ('classdef', 'funcdef') and node.children[-1].type == 'suite':
                    new_nodes.append(node)
                break

            new_nodes.append(node)

        if not new_nodes:
            return [], tos

        last_node = new_nodes[-1]
        line_offset_index = -1
        if last_node.type in ('classdef', 'funcdef'):
            suite = last_node.children[-1]
            if suite.type == 'suite':
                suite_tos = _NodesStackNode(suite)
                # Don't need to pass line_offset here, it's already done by the
                # parent.
                suite_nodes, recursive_tos = self._copy_nodes(
                    suite_tos, suite.children, until_line, line_offset)
                if len(suite_nodes) < 2:
                    # A suite only with newline is not valid.
                    new_nodes.pop()
                else:
                    suite_tos.parent = tos
                    new_tos = recursive_tos
                    line_offset_index = -2

        elif (new_nodes[-1].type in ('error_leaf', 'error_node') or
                          _is_flow_node(new_nodes[-1])):
            # Error leafs/nodes don't have a defined start/end. Error
            # nodes might not end with a newline (e.g. if there's an
            # open `(`). Therefore ignore all of them unless they are
            # succeeded with valid parser state.
            # If we copy flows at the end, they might be continued
            # after the copy limit (in the new parser).
            # In this while loop we try to remove until we find a newline.
            new_nodes.pop()
            while new_nodes:
                last_node = new_nodes[-1]
                if last_node.get_last_leaf().type == 'newline':
                    break
                new_nodes.pop()

        if new_nodes:
            try:
                last_line_offset_leaf = new_nodes[line_offset_index].get_last_leaf()
            except IndexError:
                line_offset = 0
                # In this case we don't have to calculate an offset, because
                # there's no children to be managed.
                last_line_offset_leaf = None
            tos.add(new_nodes, line_offset, last_line_offset_leaf)
        return new_nodes, new_tos

    def _update_tos(self, tree_node):
        if tree_node.type in ('suite', 'file_input'):
            self._tos = _NodesStackNode(tree_node, self._tos)
            self._tos.add(list(tree_node.children))
            self._update_tos(tree_node.children[-1])
        elif tree_node.type in ('classdef', 'funcdef'):
            self._update_tos(tree_node.children[-1])

    def close(self):
        while self._tos is not None:
            self._close_tos()

        # Add an endmarker.
        try:
            last_leaf = self._module.get_last_leaf()
            end_pos = list(last_leaf.end_pos)
        except IndexError:
            end_pos = [1, 0]
        lines = splitlines(self.prefix)
        assert len(lines) > 0
        if len(lines) == 1:
            end_pos[1] += len(lines[0])
        else:
            end_pos[0] += len(lines) - 1
            end_pos[1] = len(lines[-1])

        endmarker = EndMarker('', tuple(end_pos), self.prefix + self._last_prefix)
        endmarker.parent = self._module
        self._module.children.append(endmarker)
