# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
# For details: https://bitbucket.org/ned/coveragepy/src/default/NOTICE.txt

"""Code parsing for coverage.py."""

import collections
import dis
import re
import token
import tokenize

from coverage.backward import range    # pylint: disable=redefined-builtin
from coverage.backward import bytes_to_ints
from coverage.bytecode import ByteCodes, CodeObjects
from coverage.misc import contract, nice_pair, expensive, join_regex
from coverage.misc import CoverageException, NoSource, NotPython
from coverage.phystokens import compile_unicode, generate_tokens


class PythonParser(object):
    """Parse code to find executable lines, excluded lines, etc."""

    @contract(text='unicode|None')
    def __init__(self, text=None, filename=None, exclude=None):
        """
        Source can be provided as `text`, the text itself, or `filename`, from
        which the text will be read.  Excluded lines are those that match
        `exclude`, a regex.

        """
        assert text or filename, "PythonParser needs either text or filename"
        self.filename = filename or "<code>"
        self.text = text
        if not self.text:
            from coverage.python import get_python_source
            try:
                self.text = get_python_source(self.filename)
            except IOError as err:
                raise NoSource(
                    "No source for code: '%s': %s" % (self.filename, err)
                )

        self.exclude = exclude

        self.show_tokens = False

        # The text lines of the parsed code.
        self.lines = self.text.split('\n')

        # The line numbers of excluded lines of code.
        self.excluded = set()

        # The line numbers of docstring lines.
        self.docstrings = set()

        # The line numbers of class definitions.
        self.classdefs = set()

        # A dict mapping line numbers to (lo,hi) for multi-line statements.
        self.multiline = {}

        # The line numbers that start statements.
        self.statement_starts = set()

        # Lazily-created ByteParser and arc data.
        self._byte_parser = None
        self._all_arcs = None

    @property
    def byte_parser(self):
        """Create a ByteParser on demand."""
        if not self._byte_parser:
            self._byte_parser = ByteParser(self.text, filename=self.filename)
        return self._byte_parser

    def lines_matching(self, *regexes):
        """Find the lines matching one of a list of regexes.

        Returns a set of line numbers, the lines that contain a match for one
        of the regexes in `regexes`.  The entire line needn't match, just a
        part of it.

        """
        regex_c = re.compile(join_regex(regexes))
        matches = set()
        for i, ltext in enumerate(self.lines, start=1):
            if regex_c.search(ltext):
                matches.add(i)
        return matches

    def _raw_parse(self):
        """Parse the source to find the interesting facts about its lines.

        A handful of member fields are updated.

        """
        # Find lines which match an exclusion pattern.
        if self.exclude:
            self.excluded = self.lines_matching(self.exclude)

        # Tokenize, to find excluded suites, to find docstrings, and to find
        # multi-line statements.
        indent = 0
        exclude_indent = 0
        excluding = False
        prev_toktype = token.INDENT
        first_line = None
        empty = True

        tokgen = generate_tokens(self.text)
        for toktype, ttext, (slineno, _), (elineno, _), ltext in tokgen:
            if self.show_tokens:                # pragma: not covered
                print("%10s %5s %-20r %r" % (
                    tokenize.tok_name.get(toktype, toktype),
                    nice_pair((slineno, elineno)), ttext, ltext
                ))
            if toktype == token.INDENT:
                indent += 1
            elif toktype == token.DEDENT:
                indent -= 1
            elif toktype == token.NAME and ttext == 'class':
                # Class definitions look like branches in the byte code, so
                # we need to exclude them.  The simplest way is to note the
                # lines with the 'class' keyword.
                self.classdefs.add(slineno)
            elif toktype == token.OP and ttext == ':':
                if not excluding and elineno in self.excluded:
                    # Start excluding a suite.  We trigger off of the colon
                    # token so that the #pragma comment will be recognized on
                    # the same line as the colon.
                    exclude_indent = indent
                    excluding = True
            elif toktype == token.STRING and prev_toktype == token.INDENT:
                # Strings that are first on an indented line are docstrings.
                # (a trick from trace.py in the stdlib.) This works for
                # 99.9999% of cases.  For the rest (!) see:
                # http://stackoverflow.com/questions/1769332/x/1769794#1769794
                self.docstrings.update(range(slineno, elineno+1))
            elif toktype == token.NEWLINE:
                if first_line is not None and elineno != first_line:
                    # We're at the end of a line, and we've ended on a
                    # different line than the first line of the statement,
                    # so record a multi-line range.
                    for l in range(first_line, elineno+1):
                        self.multiline[l] = first_line
                first_line = None

            if ttext.strip() and toktype != tokenize.COMMENT:
                # A non-whitespace token.
                empty = False
                if first_line is None:
                    # The token is not whitespace, and is the first in a
                    # statement.
                    first_line = slineno
                    # Check whether to end an excluded suite.
                    if excluding and indent <= exclude_indent:
                        excluding = False
                    if excluding:
                        self.excluded.add(elineno)

            prev_toktype = toktype

        # Find the starts of the executable statements.
        if not empty:
            self.statement_starts.update(self.byte_parser._find_statements())

    def first_line(self, line):
        """Return the first line number of the statement including `line`."""
        first_line = self.multiline.get(line)
        if first_line:
            return first_line
        else:
            return line

    def first_lines(self, lines):
        """Map the line numbers in `lines` to the correct first line of the
        statement.

        Returns a set of the first lines.

        """
        return set(self.first_line(l) for l in lines)

    def translate_lines(self, lines):
        """Implement `FileReporter.translate_lines`."""
        return self.first_lines(lines)

    def translate_arcs(self, arcs):
        """Implement `FileReporter.translate_arcs`."""
        return [
            (self.first_line(a), self.first_line(b))
            for (a, b) in arcs
        ]

    @expensive
    def parse_source(self):
        """Parse source text to find executable lines, excluded lines, etc.

        Return values are 1) a set of executable line numbers, and 2) a set of
        excluded line numbers.

        Reported line numbers are normalized to the first line of multi-line
        statements.

        """
        try:
            self._raw_parse()
        except (tokenize.TokenError, IndentationError) as err:
            if hasattr(err, "lineno"):
                lineno = err.lineno         # IndentationError
            else:
                lineno = err.args[1][0]     # TokenError
            raise NotPython(
                u"Couldn't parse '%s' as Python source: '%s' at line %d" % (
                    self.filename, err.args[0], lineno
                )
            )

        excluded_lines = self.first_lines(self.excluded)
        ignore = set()
        ignore.update(excluded_lines)
        ignore.update(self.docstrings)
        starts = self.statement_starts - ignore
        lines = self.first_lines(starts)
        lines -= ignore

        return lines, excluded_lines

    def arcs(self):
        """Get information about the arcs available in the code.

        Returns a set of line number pairs.  Line numbers have been normalized
        to the first line of multi-line statements.

        """
        if self._all_arcs is None:
            self._all_arcs = set()
            for l1, l2 in self.byte_parser._all_arcs():
                fl1 = self.first_line(l1)
                fl2 = self.first_line(l2)
                if fl1 != fl2:
                    self._all_arcs.add((fl1, fl2))
        return self._all_arcs

    def exit_counts(self):
        """Get a count of exits from that each line.

        Excluded lines are excluded.

        """
        excluded_lines = self.first_lines(self.excluded)
        exit_counts = collections.defaultdict(int)
        for l1, l2 in self.arcs():
            if l1 < 0:
                # Don't ever report -1 as a line number
                continue
            if l1 in excluded_lines:
                # Don't report excluded lines as line numbers.
                continue
            if l2 in excluded_lines:
                # Arcs to excluded lines shouldn't count.
                continue
            exit_counts[l1] += 1

        # Class definitions have one extra exit, so remove one for each:
        for l in self.classdefs:
            # Ensure key is there: class definitions can include excluded lines.
            if l in exit_counts:
                exit_counts[l] -= 1

        return exit_counts


## Opcodes that guide the ByteParser.

def _opcode(name):
    """Return the opcode by name from the dis module."""
    return dis.opmap[name]


def _opcode_set(*names):
    """Return a set of opcodes by the names in `names`."""
    s = set()
    for name in names:
        try:
            s.add(_opcode(name))
        except KeyError:
            pass
    return s

# Opcodes that leave the code object.
OPS_CODE_END = _opcode_set('RETURN_VALUE')

# Opcodes that unconditionally end the code chunk.
OPS_CHUNK_END = _opcode_set(
    'JUMP_ABSOLUTE', 'JUMP_FORWARD', 'RETURN_VALUE', 'RAISE_VARARGS',
    'BREAK_LOOP', 'CONTINUE_LOOP',
)

# Opcodes that unconditionally begin a new code chunk.  By starting new chunks
# with unconditional jump instructions, we neatly deal with jumps to jumps
# properly.
OPS_CHUNK_BEGIN = _opcode_set('JUMP_ABSOLUTE', 'JUMP_FORWARD')

# Opcodes that push a block on the block stack.
OPS_PUSH_BLOCK = _opcode_set(
    'SETUP_LOOP', 'SETUP_EXCEPT', 'SETUP_FINALLY', 'SETUP_WITH'
)

# Block types for exception handling.
OPS_EXCEPT_BLOCKS = _opcode_set('SETUP_EXCEPT', 'SETUP_FINALLY')

# Opcodes that pop a block from the block stack.
OPS_POP_BLOCK = _opcode_set('POP_BLOCK')

# Opcodes that have a jump destination, but aren't really a jump.
OPS_NO_JUMP = OPS_PUSH_BLOCK

# Individual opcodes we need below.
OP_BREAK_LOOP = _opcode('BREAK_LOOP')
OP_END_FINALLY = _opcode('END_FINALLY')
OP_COMPARE_OP = _opcode('COMPARE_OP')
COMPARE_EXCEPTION = 10  # just have to get this constant from the code.
OP_LOAD_CONST = _opcode('LOAD_CONST')
OP_RETURN_VALUE = _opcode('RETURN_VALUE')


class ByteParser(object):
    """Parse byte codes to understand the structure of code."""

    @contract(text='unicode')
    def __init__(self, text, code=None, filename=None):
        self.text = text
        if code:
            self.code = code
        else:
            try:
                self.code = compile_unicode(text, filename, "exec")
            except SyntaxError as synerr:
                raise NotPython(
                    u"Couldn't parse '%s' as Python source: '%s' at line %d" % (
                        filename, synerr.msg, synerr.lineno
                    )
                )

        # Alternative Python implementations don't always provide all the
        # attributes on code objects that we need to do the analysis.
        for attr in ['co_lnotab', 'co_firstlineno', 'co_consts', 'co_code']:
            if not hasattr(self.code, attr):
                raise CoverageException(
                    "This implementation of Python doesn't support code analysis.\n"
                    "Run coverage.py under CPython for this command."
                )

    def child_parsers(self):
        """Iterate over all the code objects nested within this one.

        The iteration includes `self` as its first value.

        """
        children = CodeObjects(self.code)
        return (ByteParser(self.text, code=c) for c in children)

    def _bytes_lines(self):
        """Map byte offsets to line numbers in `code`.

        Uses co_lnotab described in Python/compile.c to map byte offsets to
        line numbers.  Produces a sequence: (b0, l0), (b1, l1), ...

        Only byte offsets that correspond to line numbers are included in the
        results.

        """
        # Adapted from dis.py in the standard library.
        byte_increments = bytes_to_ints(self.code.co_lnotab[0::2])
        line_increments = bytes_to_ints(self.code.co_lnotab[1::2])

        last_line_num = None
        line_num = self.code.co_firstlineno
        byte_num = 0
        for byte_incr, line_incr in zip(byte_increments, line_increments):
            if byte_incr:
                if line_num != last_line_num:
                    yield (byte_num, line_num)
                    last_line_num = line_num
                byte_num += byte_incr
            line_num += line_incr
        if line_num != last_line_num:
            yield (byte_num, line_num)

    def _find_statements(self):
        """Find the statements in `self.code`.

        Produce a sequence of line numbers that start statements.  Recurses
        into all code objects reachable from `self.code`.

        """
        for bp in self.child_parsers():
            # Get all of the lineno information from this code.
            for _, l in bp._bytes_lines():
                yield l

    def _block_stack_repr(self, block_stack):               # pragma: debugging
        """Get a string version of `block_stack`, for debugging."""
        blocks = ", ".join(
            "(%s, %r)" % (dis.opname[b[0]], b[1]) for b in block_stack
        )
        return "[" + blocks + "]"

    def _split_into_chunks(self):
        """Split the code object into a list of `Chunk` objects.

        Each chunk is only entered at its first instruction, though there can
        be many exits from a chunk.

        Returns a list of `Chunk` objects.

        """
        # The list of chunks so far, and the one we're working on.
        chunks = []
        chunk = None

        # A dict mapping byte offsets of line starts to the line numbers.
        bytes_lines_map = dict(self._bytes_lines())

        # The block stack: loops and try blocks get pushed here for the
        # implicit jumps that can occur.
        # Each entry is a tuple: (block type, destination)
        block_stack = []

        # Some op codes are followed by branches that should be ignored.  This
        # is a count of how many ignores are left.
        ignore_branch = 0

        # We have to handle the last two bytecodes specially.
        ult = penult = None

        # Get a set of all of the jump-to points.
        jump_to = set()
        bytecodes = list(ByteCodes(self.code.co_code))
        for bc in bytecodes:
            if bc.jump_to >= 0:
                jump_to.add(bc.jump_to)

        chunk_lineno = 0

        # Walk the byte codes building chunks.
        for bc in bytecodes:
            # Maybe have to start a new chunk.
            start_new_chunk = False
            first_chunk = False
            if bc.offset in bytes_lines_map:
                # Start a new chunk for each source line number.
                start_new_chunk = True
                chunk_lineno = bytes_lines_map[bc.offset]
                first_chunk = True
            elif bc.offset in jump_to:
                # To make chunks have a single entrance, we have to make a new
                # chunk when we get to a place some bytecode jumps to.
                start_new_chunk = True
            elif bc.op in OPS_CHUNK_BEGIN:
                # Jumps deserve their own unnumbered chunk.  This fixes
                # problems with jumps to jumps getting confused.
                start_new_chunk = True

            if not chunk or start_new_chunk:
                if chunk:
                    chunk.exits.add(bc.offset)
                chunk = Chunk(bc.offset, chunk_lineno, first_chunk)
                if not chunks:
                    # The very first chunk of a code object is always an
                    # entrance.
                    chunk.entrance = True
                chunks.append(chunk)

            # Look at the opcode.
            if bc.jump_to >= 0 and bc.op not in OPS_NO_JUMP:
                if ignore_branch:
                    # Someone earlier wanted us to ignore this branch.
                    ignore_branch -= 1
                else:
                    # The opcode has a jump, it's an exit for this chunk.
                    chunk.exits.add(bc.jump_to)

            if bc.op in OPS_CODE_END:
                # The opcode can exit the code object.
                chunk.exits.add(-self.code.co_firstlineno)
            if bc.op in OPS_PUSH_BLOCK:
                # The opcode adds a block to the block_stack.
                block_stack.append((bc.op, bc.jump_to))
            if bc.op in OPS_POP_BLOCK:
                # The opcode pops a block from the block stack.
                block_stack.pop()
            if bc.op in OPS_CHUNK_END:
                # This opcode forces the end of the chunk.
                if bc.op == OP_BREAK_LOOP:
                    # A break is implicit: jump where the top of the
                    # block_stack points.
                    chunk.exits.add(block_stack[-1][1])
                chunk = None
            if bc.op == OP_END_FINALLY:
                # For the finally clause we need to find the closest exception
                # block, and use its jump target as an exit.
                for block in reversed(block_stack):
                    if block[0] in OPS_EXCEPT_BLOCKS:
                        chunk.exits.add(block[1])
                        break
            if bc.op == OP_COMPARE_OP and bc.arg == COMPARE_EXCEPTION:
                # This is an except clause.  We want to overlook the next
                # branch, so that except's don't count as branches.
                ignore_branch += 1

            penult = ult
            ult = bc

        if chunks:
            # The last two bytecodes could be a dummy "return None" that
            # shouldn't be counted as real code. Every Python code object seems
            # to end with a return, and a "return None" is inserted if there
            # isn't an explicit return in the source.
            if ult and penult:
                if penult.op == OP_LOAD_CONST and ult.op == OP_RETURN_VALUE:
                    if self.code.co_consts[penult.arg] is None:
                        # This is "return None", but is it dummy?  A real line
                        # would be a last chunk all by itself.
                        if chunks[-1].byte != penult.offset:
                            ex = -self.code.co_firstlineno
                            # Split the last chunk
                            last_chunk = chunks[-1]
                            last_chunk.exits.remove(ex)
                            last_chunk.exits.add(penult.offset)
                            chunk = Chunk(
                                penult.offset, last_chunk.line, False
                            )
                            chunk.exits.add(ex)
                            chunks.append(chunk)

            # Give all the chunks a length.
            chunks[-1].length = bc.next_offset - chunks[-1].byte
            for i in range(len(chunks)-1):
                chunks[i].length = chunks[i+1].byte - chunks[i].byte

        #self.validate_chunks(chunks)
        return chunks

    def validate_chunks(self, chunks):                      # pragma: debugging
        """Validate the rule that chunks have a single entrance."""
        # starts is the entrances to the chunks
        starts = set(ch.byte for ch in chunks)
        for ch in chunks:
            assert all((ex in starts or ex < 0) for ex in ch.exits)

    def _arcs(self):
        """Find the executable arcs in the code.

        Yields pairs: (from,to).  From and to are integer line numbers.  If
        from is < 0, then the arc is an entrance into the code object.  If to
        is < 0, the arc is an exit from the code object.

        """
        chunks = self._split_into_chunks()

        # A map from byte offsets to the chunk starting at that offset.
        byte_chunks = dict((c.byte, c) for c in chunks)

        # Traverse from the first chunk in each line, and yield arcs where
        # the trace function will be invoked.
        for chunk in chunks:
            if chunk.entrance:
                yield (-1, chunk.line)

            if not chunk.first:
                continue

            chunks_considered = set()
            chunks_to_consider = [chunk]
            while chunks_to_consider:
                # Get the chunk we're considering, and make sure we don't
                # consider it again.
                this_chunk = chunks_to_consider.pop()
                chunks_considered.add(this_chunk)

                # For each exit, add the line number if the trace function
                # would be triggered, or add the chunk to those being
                # considered if not.
                for ex in this_chunk.exits:
                    if ex < 0:
                        yield (chunk.line, ex)
                    else:
                        next_chunk = byte_chunks[ex]
                        if next_chunk in chunks_considered:
                            continue

                        # The trace function is invoked if visiting the first
                        # bytecode in a line, or if the transition is a
                        # backward jump.
                        backward_jump = next_chunk.byte < this_chunk.byte
                        if next_chunk.first or backward_jump:
                            if next_chunk.line != chunk.line:
                                yield (chunk.line, next_chunk.line)
                        else:
                            chunks_to_consider.append(next_chunk)

    def _all_chunks(self):
        """Returns a list of `Chunk` objects for this code and its children.

        See `_split_into_chunks` for details.

        """
        chunks = []
        for bp in self.child_parsers():
            chunks.extend(bp._split_into_chunks())

        return chunks

    def _all_arcs(self):
        """Get the set of all arcs in this code object and its children.

        See `_arcs` for details.

        """
        arcs = set()
        for bp in self.child_parsers():
            arcs.update(bp._arcs())

        return arcs


class Chunk(object):
    """A sequence of byte codes with a single entrance.

    To analyze byte code, we have to divide it into chunks, sequences of byte
    codes such that each chunk has only one entrance, the first instruction in
    the block.

    This is almost the CS concept of `basic block`_, except that we're willing
    to have many exits from a chunk, and "basic block" is a more cumbersome
    term.

    .. _basic block: http://en.wikipedia.org/wiki/Basic_block

    `byte` is the offset to the bytecode starting this chunk.

    `line` is the source line number containing this chunk.

    `first` is true if this is the first chunk in the source line.

    An exit < 0 means the chunk can leave the code (return).  The exit is
    the negative of the starting line number of the code block.

    The `entrance` attribute is a boolean indicating whether the code object
    can be entered at this chunk.

    """
    def __init__(self, byte, line, first):
        self.byte = byte
        self.line = line
        self.first = first
        self.length = 0
        self.entrance = False
        self.exits = set()

    def __repr__(self):
        return "<%d+%d @%d%s%s %r>" % (
            self.byte,
            self.length,
            self.line,
            "!" if self.first else "",
            "v" if self.entrance else "",
            list(self.exits),
        )
