#!/usr/bin/env python3
# Copyright 2018 The Emscripten Authors.  All rights reserved.
# Emscripten is available under two separate licenses, the MIT license and the
# University of Illinois/NCSA Open Source License.  Both these licenses can be
# found in the LICENSE file.

"""Utility tools that extracts DWARF information encoded in a wasm output
produced by the LLVM tools, and encodes it as a wasm source map. Additionally,
it can collect original sources, change files prefixes, and strip debug
sections from a wasm file.
"""

import argparse
from collections import OrderedDict
import json
import logging
from math import floor, log
import os
import re
from subprocess import Popen, PIPE
from pathlib import Path
import sys

sys.path.insert(1, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))


logger = logging.getLogger('wasm-sourcemap')


def parse_args():
  parser = argparse.ArgumentParser(prog='wasm-sourcemap.py', description=__doc__)
  parser.add_argument('wasm', help='wasm file')
  parser.add_argument('-o', '--output', help='output source map')
  parser.add_argument('-p', '--prefix', nargs='*', help='replace source debug filename prefix for source map', default=[])
  parser.add_argument('-s', '--sources', action='store_true', help='read and embed source files from file system into source map')
  parser.add_argument('-l', '--load-prefix', nargs='*', help='replace source debug filename prefix for reading sources from file system (see also --sources)', default=[])
  parser.add_argument('-w', nargs='?', help='set output wasm file')
  parser.add_argument('-x', '--strip', action='store_true', help='removes debug and linking sections')
  parser.add_argument('-u', '--source-map-url', nargs='?', help='specifies sourceMappingURL section contest')
  parser.add_argument('--dwarfdump', help="path to llvm-dwarfdump executable")
  parser.add_argument('--dwarfdump-output', nargs='?', help=argparse.SUPPRESS)
  parser.add_argument('--basepath', help='base path for source files, which will be relative to this')
  return parser.parse_args()


class Prefixes:
  def __init__(self, args):
    prefixes = []
    for p in args:
      if '=' in p:
        prefix, replacement = p.split('=')
        prefixes.append({'prefix': prefix, 'replacement': replacement})
      else:
        prefixes.append({'prefix': p, 'replacement': None})
    self.prefixes = prefixes
    self.cache = {}

  def resolve(self, name):
    if name in self.cache:
      return self.cache[name]

    for p in self.prefixes:
      if name.startswith(p['prefix']):
        if p['replacement'] is None:
          result = name[len(p['prefix'])::]
        else:
          result = p['replacement'] + name[len(p['prefix'])::]
        break
    self.cache[name] = result
    return result


# SourceMapPrefixes contains resolver for file names that are:
#  - "sources" is for names that output to source maps JSON
#  - "load" is for paths that used to load source text
class SourceMapPrefixes:
  def __init__(self, sources, load):
    self.sources = sources
    self.load = load

  def provided(self):
    return bool(self.sources.prefixes or self.load.prefixes)


def encode_vlq(n):
  VLQ_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  x = (n << 1) if n >= 0 else ((-n << 1) + 1)
  result = ""
  while x > 31:
    result = result + VLQ_CHARS[32 + (x & 31)]
    x = x >> 5
  return result + VLQ_CHARS[x]


def read_var_uint(wasm, pos):
  n = 0
  shift = 0
  b = ord(wasm[pos:pos + 1])
  pos = pos + 1
  while b >= 128:
    n = n | ((b - 128) << shift)
    b = ord(wasm[pos:pos + 1])
    pos = pos + 1
    shift += 7
  return n + (b << shift), pos


def strip_debug_sections(wasm):
  logger.debug('Strip debug sections')
  pos = 8
  stripped = wasm[:pos]

  while pos < len(wasm):
    section_start = pos
    section_id, pos_ = read_var_uint(wasm, pos)
    section_size, section_body = read_var_uint(wasm, pos_)
    pos = section_body + section_size
    if section_id == 0:
      name_len, name_pos = read_var_uint(wasm, section_body)
      name_end = name_pos + name_len
      name = wasm[name_pos:name_end]
      if name == "linking" or name == "sourceMappingURL" or name.startswith("reloc..debug_") or name.startswith(".debug_"):
        continue  # skip debug related sections
    stripped = stripped + wasm[section_start:pos]

  return stripped


def encode_uint_var(n):
  result = bytearray()
  while n > 127:
    result.append(128 | (n & 127))
    n = n >> 7
  result.append(n)
  return bytes(result)


def append_source_mapping(wasm, url):
  logger.debug('Append sourceMappingURL section')
  section_name = "sourceMappingURL"
  section_content = encode_uint_var(len(section_name)) + section_name + encode_uint_var(len(url)) + url
  return wasm + encode_uint_var(0) + encode_uint_var(len(section_content)) + section_content


def get_code_section_offset(wasm):
  logger.debug('Read sections index')
  pos = 8

  while pos < len(wasm):
    section_id, pos_ = read_var_uint(wasm, pos)
    section_size, pos = read_var_uint(wasm, pos_)
    if section_id == 10:
      return pos
    pos = pos + section_size


def remove_dead_entries(entries):
  # Remove entries for dead functions. It is a heuristics to ignore data if the
  # function starting address near to 0 (is equal to its size field length).
  block_start = 0
  cur_entry = 0
  while cur_entry < len(entries):
    if not entries[cur_entry]['eos']:
      cur_entry += 1
      continue
    fn_start = entries[block_start]['address']
    # Calculate the LEB encoded function size (including size field)
    fn_size_length = floor(log(entries[cur_entry]['address'] - fn_start + 1, 128)) + 1
    min_live_offset = 1 + fn_size_length # 1 byte is for code section entries
    if fn_start < min_live_offset:
      # Remove dead code debug info block.
      del entries[block_start:cur_entry + 1]
      cur_entry = block_start
      continue
    cur_entry += 1
    block_start = cur_entry


def read_dwarf_entries(wasm, options):
  if options.dwarfdump_output:
    output = Path(options.dwarfdump_output).read_bytes()
  elif options.dwarfdump:
    logger.debug('Reading DWARF information from %s' % wasm)
    if not os.path.exists(options.dwarfdump):
      logger.error('llvm-dwarfdump not found: ' + options.dwarfdump)
      sys.exit(1)
    process = Popen([options.dwarfdump, '-debug-info', '-debug-line', '--recurse-depth=0', wasm], stdout=PIPE)
    output, err = process.communicate()
    exit_code = process.wait()
    if exit_code != 0:
      logger.error('Error during llvm-dwarfdump execution (%s)' % exit_code)
      sys.exit(1)
  else:
    logger.error('Please specify either --dwarfdump or --dwarfdump-output')
    sys.exit(1)

  entries = []
  debug_line_chunks = re.split(r"debug_line\[(0x[0-9a-f]*)\]", output.decode('utf-8'))
  maybe_debug_info_content = debug_line_chunks[0]
  for i in range(1, len(debug_line_chunks), 2):
    stmt_list = debug_line_chunks[i]
    comp_dir_match = re.search(r"DW_AT_stmt_list\s+\(" + stmt_list + r"\)\s+" +
                               r"DW_AT_comp_dir\s+\(\"([^\"]+)", maybe_debug_info_content)
    comp_dir = comp_dir_match.group(1) if comp_dir_match is not None else ""

    line_chunk = debug_line_chunks[i + 1]

    # include_directories[  1] = "/Users/yury/Work/junk/sqlite-playground/src"
    # file_names[  1]:
    #            name: "playground.c"
    #       dir_index: 1
    #        mod_time: 0x00000000
    #          length: 0x00000000
    #
    # Address            Line   Column File   ISA Discriminator Flags
    # ------------------ ------ ------ ------ --- ------------- -------------
    # 0x0000000000000006     22      0      1   0             0  is_stmt
    # 0x0000000000000007     23     10      1   0             0  is_stmt prologue_end
    # 0x000000000000000f     23      3      1   0             0
    # 0x0000000000000010     23      3      1   0             0  end_sequence
    # 0x0000000000000011     28      0      1   0             0  is_stmt

    include_directories = {'0': comp_dir}
    for dir in re.finditer(r"include_directories\[\s*(\d+)\] = \"([^\"]*)", line_chunk):
      include_directories[dir.group(1)] = dir.group(2)

    files = {}
    for file in re.finditer(r"file_names\[\s*(\d+)\]:\s+name: \"([^\"]*)\"\s+dir_index: (\d+)", line_chunk):
      dir = include_directories[file.group(3)]
      file_path = (dir + '/' if file.group(2)[0] != '/' else '') + file.group(2)
      files[file.group(1)] = file_path

    for line in re.finditer(r"\n0x([0-9a-f]+)\s+(\d+)\s+(\d+)\s+(\d+)(.*?end_sequence)?", line_chunk):
      entry = {'address': int(line.group(1), 16), 'line': int(line.group(2)), 'column': int(line.group(3)), 'file': files[line.group(4)], 'eos': line.group(5) is not None}
      if not entry['eos']:
        entries.append(entry)
      else:
        # move end of function to the last END operator
        entry['address'] -= 1
        if entries[-1]['address'] == entry['address']:
          # last entry has the same address, reusing
          entries[-1]['eos'] = True
        else:
          entries.append(entry)

  remove_dead_entries(entries)

  # return entries sorted by the address field
  return sorted(entries, key=lambda entry: entry['address'])


def normalize_path(path):
  return path.replace('\\', '/').replace('//', '/')


def build_sourcemap(entries, code_section_offset, prefixes, collect_sources, base_path):
  sources = []
  sources_content = [] if collect_sources else None
  mappings = []
  sources_map = {}
  last_address = 0
  last_source_id = 0
  last_line = 1
  last_column = 1
  for entry in entries:
    line = entry['line']
    column = entry['column']
    # ignore entries with line 0
    if line == 0:
      continue
    # start at least at column 1
    if column == 0:
      column = 1
    address = entry['address'] + code_section_offset
    file_name = entry['file']
    file_name = normalize_path(file_name)
    # if prefixes were provided, we use that; otherwise, we emit a relative
    # path
    if prefixes.provided():
      source_name = prefixes.sources.resolve(file_name)
    else:
      try:
        file_name = os.path.relpath(file_name, base_path)
      except ValueError:
        file_name = os.path.abspath(file_name)
      file_name = normalize_path(file_name)
      source_name = file_name
    if source_name not in sources_map:
      source_id = len(sources)
      sources_map[source_name] = source_id
      sources.append(source_name)
      if collect_sources:
        load_name = prefixes.load.resolve(file_name)
        try:
          with open(load_name, 'r') as infile:
            source_content = infile.read()
          sources_content.append(source_content)
        except IOError:
          print('Failed to read source: %s' % load_name)
          sources_content.append(None)
    else:
      source_id = sources_map[source_name]

    address_delta = address - last_address
    source_id_delta = source_id - last_source_id
    line_delta = line - last_line
    column_delta = column - last_column
    mappings.append(encode_vlq(address_delta) + encode_vlq(source_id_delta) + encode_vlq(line_delta) + encode_vlq(column_delta))
    last_address = address
    last_source_id = source_id
    last_line = line
    last_column = column
  return OrderedDict([('version', 3),
                      ('names', []),
                      ('sources', sources),
                      ('sourcesContent', sources_content),
                      ('mappings', ','.join(mappings))])


def main():
  options = parse_args()

  wasm_input = options.wasm
  with open(wasm_input, 'rb') as infile:
    wasm = infile.read()

  entries = read_dwarf_entries(wasm_input, options)

  code_section_offset = get_code_section_offset(wasm)

  prefixes = SourceMapPrefixes(sources=Prefixes(options.prefix), load=Prefixes(options.load_prefix))

  logger.debug('Saving to %s' % options.output)
  map = build_sourcemap(entries, code_section_offset, prefixes, options.sources, options.basepath)
  with open(options.output, 'w') as outfile:
    json.dump(map, outfile, separators=(',', ':'))

  if options.strip:
    wasm = strip_debug_sections(wasm)

  if options.source_map_url:
    wasm = append_source_mapping(wasm, options.source_map_url)

  if options.w:
    logger.debug('Saving wasm to %s' % options.w)
    with open(options.w, 'wb') as outfile:
      outfile.write(wasm)

  logger.debug('Done')
  return 0


if __name__ == '__main__':
  logging.basicConfig(level=logging.DEBUG if os.environ.get('EMCC_DEBUG') else logging.INFO)
  sys.exit(main())