#!/usr/bin/env python3.8
# Copyright 2019 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import json
import textwrap
import sys

def usage():
  print('Usage:\n'
        '  magma.h.gen.py INPUT OUTPUT\n'
        '    INPUT    json file containing the magma interface definition\n'
        '    OUTPUT   destination path for the magma header file to generate\n'
        '  Example: ./magma.h.gen.py ./magma.json ./magma.h\n'
        '  Generates the magma header based on a provided json definition.\n'
        '  Description fields are generated in the Doxygen format.')

# Generate a string for a comment with a Doxygen tag, wrapping text as necessary.
def format_comment(type, comment):
  wrap = 100
  prefix_first = '/// \\' + type + ' '
  prefix_len = len(prefix_first)
  prefix_rest = '///'.ljust(prefix_len)
  lines = textwrap.wrap(comment, wrap - prefix_len)
  formatted = [f'{prefix_first}{lines[0]}']
  formatted.extend(f'{prefix_rest}{line}' for line in lines[1:])
  return '\n'.join(formatted)

# Generate a string for a magma export object, including its comment block.
def format_export(export):
  # Leading comment
  lines = [f'///\n{format_comment("brief", export["description"])}']
  lines.extend(format_comment('param', f'{arg["name"]} {arg["description"]}')
               for arg in export['arguments'])
  lines.append('///')
  # Function signature
  lines.append(f'{export["type"]} {export["name"]}(')
  lines.append(',\n'.join(f'    {arg["type"]} {arg["name"]}'
                          for arg in export['arguments']))
  lines[-1] = f'{lines[-1]});'
  lines.append('')
  return '\n'.join(lines)

# License string for the top of the file.
def license():
  return ('// Copyright 2016 The Fuchsia Authors. All rights reserved.\n'
          '// Use of this source code is governed by a BSD-style license that can be\n'
          '// found in the LICENSE file.\n')

# Guard macro that goes at the beginning/end of the header (after license).
def guards(begin):
  macro = 'SRC_GRAPHICS_LIB_MAGMA_INCLUDE_MAGMA_ABI_MAGMA_H_'
  if begin:
    return f'#ifndef {macro}\n#define {macro}\n'
  return f'#endif // {macro}'

# Begin/end C linkage scope.
def externs(begin):
  if begin:
    return '#if defined(__cplusplus)\nextern "C" {\n#endif\n'
  return '#if defined(__cplusplus)\n}\n#endif\n'

# Includes list.
def includes():
  return ('#include "magma_common_defs.h"\n'
          '#include <stdint.h>\n')

# Warning comment about auto-generation.
def genwarning():
  return ('// NOTE: DO NOT EDIT THIS FILE!\n'
          '// It is automatically generated by //src/graphics/lib/magma/include/magma_abi/magma.h.gen.py\n')

def genformatoff():
  return '// clang-format off\n'

def main():
  if (len(sys.argv) != 3):
    usage()
    exit(-1)
  try:
    with open(sys.argv[1], 'r') as file:
      with open(sys.argv[2], 'w') as dest:
        magma = json.load(file)['magma-interface']
        lines = [license(),
                 genwarning(),
                 genformatoff(),
                 guards(True),
                 includes(),
                 externs(True)]
        lines.extend(format_export(e) for e in magma['exports'])
        lines.append(externs(False))
        lines.append(guards(False))
        lines.append('')
        dest.write('\n'.join(lines))
  except Exception as e:
    print(f'Error accessing files: {e}')
    usage()
    exit(-2)

if __name__ == '__main__':
  sys.exit(main())