'''
Scons Builder for nanopb .proto definitions.

This tool will locate the nanopb generator and use it to generate .pb.c and
.pb.h files from the .proto files.

Basic example
-------------
# Build myproto.pb.c and myproto.pb.h from myproto.proto
myproto = env.NanopbProto("myproto")

# Link nanopb core to the program
env.Append(CPPPATH = "$NANOB")
myprog = env.Program(["myprog.c", myproto, "$NANOPB/pb_encode.c", "$NANOPB/pb_decode.c"])

Configuration options
---------------------
Normally, this script is used in the test environment of nanopb and it locates
the nanopb generator by a relative path. If this script is used in another
application, the path to nanopb root directory has to be defined:

env.SetDefault(NANOPB = "path/to/nanopb")

Additionally, the path to protoc and the options to give to protoc can be
defined manually:

env.SetDefault(PROTOC = "path/to/protoc")
env.SetDefault(PROTOCFLAGS = "--plugin=protoc-gen-nanopb=path/to/protoc-gen-nanopb")
'''

import SCons.Action
import SCons.Builder
import SCons.Util
import os.path

class NanopbWarning(SCons.Warnings.Warning):
    pass
SCons.Warnings.enableWarningClass(NanopbWarning)

def _detect_nanopb(env):
    '''Find the path to nanopb root directory.'''
    if env.has_key('NANOPB'):
        # Use nanopb dir given by user
        return env['NANOPB']
    
    p = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..', '..'))
    if os.path.isdir(p) and os.path.isfile(os.path.join(p, 'pb.h')):
        # Assume we are running under tests/site_scons/site_tools
        return p
    
    raise SCons.Errors.StopError(NanopbWarning,
        "Could not find the nanopb root directory")

def _detect_protoc(env):
    '''Find the path to the protoc compiler.'''
    if env.has_key('PROTOC'):
        # Use protoc defined by user
        return env['PROTOC']
    
    p = _detect_nanopb(env)
    p1 = os.path.join(p, 'generator-bin', 'protoc' + env['PROGSUFFIX'])
    if os.path.exists(p1):
        # Use protoc bundled with binary package
        return env['ESCAPE'](p1)
    
    p = env.WhereIs('protoc')
    if p:
        # Use protoc from path
        return env['ESCAPE'](p)
    
    raise SCons.Errors.StopError(NanopbWarning,
        "Could not find the protoc compiler")

def _detect_protocflags(env):
    '''Find the options to use for protoc.'''
    if env.has_key('PROTOCFLAGS'):
        return env['PROTOCFLAGS']
    
    p = _detect_protoc(env)
    n = _detect_nanopb(env)
    if p == os.path.join(n, 'generator-bin', 'protoc'):
        # Using the bundled protoc, no options needed
        return ''
    
    e = env['ESCAPE']
    if env['PLATFORM'] == 'win32':
        return e('--plugin=protoc-gen-nanopb=' + os.path.join(n, 'generator', 'protoc-gen-nanopb.bat'))
    else:
        return e('--plugin=protoc-gen-nanopb=' + os.path.join(n, 'generator', 'protoc-gen-nanopb'))

def _nanopb_proto_actions(source, target, env, for_signature):
    esc = env['ESCAPE']
    dirs = ' '.join(['-I' + esc(env.GetBuildPath(d)) for d in env['PROTOCPATH']])
    return '$PROTOC $PROTOCFLAGS %s --nanopb_out=. %s' % (dirs, esc(str(source[0])))

def _nanopb_proto_emitter(target, source, env):
    basename = os.path.splitext(str(source[0]))[0]
    target.append(basename + '.pb.h')
    
    if os.path.exists(basename + '.options'):
        source.append(basename + '.options')
    
    return target, source

_nanopb_proto_builder = SCons.Builder.Builder(
    generator = _nanopb_proto_actions,
    suffix = '.pb.c',
    src_suffix = '.proto',
    emitter = _nanopb_proto_emitter)
       
def generate(env):
    '''Add Builder for nanopb protos.'''
    
    env['NANOPB'] = _detect_nanopb(env)
    env['PROTOC'] = _detect_protoc(env)
    env['PROTOCFLAGS'] = _detect_protocflags(env)
    
    env.SetDefault(PROTOCPATH = ['.', os.path.join(env['NANOPB'], 'generator', 'proto')])
    
    env.SetDefault(NANOPB_PROTO_CMD = '$PROTOC $PROTOC_OPTS --nanopb_out=. $SOURCE')
    env['BUILDERS']['NanopbProto'] = _nanopb_proto_builder
    
def exists(env):
    return _detect_protoc(env) and _detect_protoc_opts(env)