#! /usr/bin/env python
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"""
Library for supporting message and service generation for all ROS
client libraries. This is mainly responsible for calculating the
md5sums and message definitions of classes.
"""

# NOTE: this should not contain any rospy-specific code. The rospy
# generator library is rospy.genpy.

import sys
import hashlib

try:
    from cStringIO import StringIO # Python 2.x
except ImportError:
    from io import StringIO # Python 3.x

from . import msgs

from .msgs import InvalidMsgSpec, MsgSpec, bare_msg_type, is_builtin
from .msg_loader import load_depends
from .srvs import SrvSpec
from . import names
from . import base

def compute_md5_text(msg_context, spec):
    """
    Compute the text used for md5 calculation. MD5 spec states that we
    removes comments and non-meaningful whitespace. We also strip
    packages names from type names. For convenience sake, constants are
    reordered ahead of other declarations, in the order that they were
    originally defined.

    :returns: text for ROS MD5-processing, ``str``
    """
    package = spec.package

    buff = StringIO()    

    for c in spec.constants:
        buff.write("%s %s=%s\n"%(c.type, c.name, c.val_text))
    for type_, name in zip(spec.types, spec.names):
        msg_type = bare_msg_type(type_)
        # md5 spec strips package names
        if is_builtin(msg_type):
            buff.write("%s %s\n"%(type_, name))
        else:
            # recursively generate md5 for subtype.  have to build up
            # dependency representation for subtype in order to
            # generate md5
            sub_pkg, _ = names.package_resource_name(msg_type)
            sub_pkg = sub_pkg or package
            sub_spec = msg_context.get_registered(msg_type)
            sub_md5 = compute_md5(msg_context, sub_spec)
            buff.write("%s %s\n"%(sub_md5, name))
    
    return buff.getvalue().strip() # remove trailing new line

def _compute_hash(msg_context, spec, hash):
    """
    subroutine of compute_md5()

    :param msg_context: :class:`MsgContext` instance to load dependencies into/from.
    :param spec: :class:`MsgSpec` to compute hash for.
    :param hash: hash instance  
    """
    # accumulate the hash
    # - root file
    if isinstance(spec, MsgSpec):
        hash.update(compute_md5_text(msg_context, spec).encode())
    elif isinstance(spec, SrvSpec):
        hash.update(compute_md5_text(msg_context, spec.request).encode())
        hash.update(compute_md5_text(msg_context, spec.response).encode())
    else:
        raise Exception("[%s] is not a message or service"%spec)   
    return hash.hexdigest()

def compute_md5(msg_context, spec):
    """
    Compute md5 hash for message/service

    :param msg_context: :class:`MsgContext` instance to load dependencies into/from.
    :param spec: :class:`MsgSpec` to compute md5 for.
    :returns: md5 hash, ``str``
    """
    return _compute_hash(msg_context, spec, hashlib.md5())

## alias
compute_md5_v2 = compute_md5

def _unique_deps(dep_list):
    uniques = []
    for d in dep_list:
        if d not in uniques:
            uniques.append(d)
    return uniques
        
def compute_full_text(msg_context, spec):
    """
    Compute full text of message/service, including text of embedded
    types.  The text of the main msg/srv is listed first. Embedded
    msg/srv files are denoted first by an 80-character '=' separator,
    followed by a type declaration line,'MSG: pkg/type', followed by
    the text of the embedded type.

    :param msg_context: :class:`MsgContext` instance to load dependencies into/from.
    :param spec: :class:`MsgSpec` to compute full text for.
    :returns: concatenated text for msg/srv file and embedded msg/srv types, ``str``
    """
    buff = StringIO()
    sep = '='*80+'\n'

    # write the text of the top-level type
    buff.write(spec.text)
    buff.write('\n')    
    # append the text of the dependencies (embedded types).  Can't use set() as we have to preserve order.
    for d in _unique_deps(msg_context.get_all_depends(spec.full_name)):
        buff.write(sep)
        buff.write("MSG: %s\n"%d)
        buff.write(msg_context.get_registered(d).text)
        buff.write('\n')
    # #1168: remove the trailing \n separator that is added by the concatenation logic
    return buff.getvalue()[:-1]

def compute_full_type_name(package_name, file_name):
    """
    Compute the full type name of message/service 'pkg/type'.

    :param package_name: name of package file is in, ``str``
    :file_name: name of the msg or srv file, ``str``
    :returns: typename in format 'pkg/type'
    :raises: :exc:`MsgGenerationException` if file_name ends with an unknown file extension
    """
    # strip extension
    for ext in (base.EXT_MSG, base.EXT_SRV):
        if file_name.endswith(ext):
            short_name = file_name[:-len(ext)]
            break
    else:
        raise base.MsgGenerationException("Processing file: '%s' - unknown file extension"% (file_name))
    return "%s/%s"%(package_name, short_name)

