# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

# This file is used to generate code in the files
# src/arrowExports.cpp and R/arrowExports.R
#
# This is similar to what compileAttributes() would do,
# with some arrow specific changes.
#
# Functions are decorated with [[arrow::export]]
# and the generated code adds a layer of protection so that
# the arrow package can be installed even when libarrow is not
#
# All the C++ code should be guarded by
#
# #if defined(ARROW_R_WITH_ARROW)
# // [[arrow::export]]
# std::shared_ptr<arrow::Array> some_function_using_arrow_api(){
#     ...
# }
# #endif


# Different flags can be used to export different features.
# [[feature::export]]
# maps to
# #if defined(ARROW_R_WITH_FEATURE)
# and each feature is written to its own set of export files.

# Ensure that all machines are sorting the same way
invisible(Sys.setlocale("LC_COLLATE", "C"))

features <- c("arrow", "dataset", "parquet", "s3", "json")

suppressPackageStartupMessages({
  library(decor)
  library(dplyr)
  library(purrr)
  library(glue)
  library(vctrs)
})

get_exported_functions <- function(decorations, export_tag) {
  out <- decorations %>%
    filter(decoration %in% paste0(export_tag, "::export")) %>%
    mutate(functions = map(context, decor:::parse_cpp_function)) %>%
    { vec_cbind(., vec_rbind(!!!pull(., functions))) } %>%
    select(-functions) %>%
    mutate(decoration = sub("::export", "", decoration))
  message(glue("*** > {n} functions decorated with [[{tags}::export]]", n = nrow(out), tags = paste0(export_tag, collapse = "|")))
  out
}

glue_collapse_data <- function(data, ..., sep = ", ", last = "") {
  res <- glue_collapse(glue_data(data, ...), sep = sep, last = last)
  if (length(res) == 0) res <- ""
  res
}

wrap_call <- function(name, return_type, args) {
  call <- glue::glue('{name}({list_params})', list_params = glue_collapse_data(args, "{name}"))
  if (return_type == "void") {
    glue::glue("\t{call};\n\treturn R_NilValue;", .trim = FALSE)
  } else {
    glue::glue("\treturn cpp11::as_sexp({call});")
  }
}

feature_available <- function(feat) {
  glue::glue(
'extern "C" SEXP _{feat}_available() {{
return Rf_ScalarLogical(
#if defined(ARROW_R_WITH_{toupper(feat)})
  TRUE
#else
  FALSE
#endif
);
}}
')
}

write_if_modified <- function(code, file) {
  old <- try(readLines(file), silent=TRUE)
  new <- unclass(unlist(strsplit(code, "\n")))
  # We don't care about changes in empty lines
  if (!identical(old[nzchar(old)], new[nzchar(new)])) {
    writeLines(con = file, code)
    # To debug why they're different if you think they shouldn't be:
    # print(waldo::compare(old[nzchar(old)], new[nzchar(new)]))
    message(glue::glue("*** > generated file `{file}`"))
  } else {
    message(glue::glue("*** > `{file}` not modified"))
  }
}

all_decorations <- cpp_decorations()
arrow_exports <- get_exported_functions(all_decorations, features)

arrow_classes <- c(
  "Table" = "arrow::Table",
  "RecordBatch" = "arrow::RecordBatch"
)

# This takes a cpp11 C wrapper and conditionally makes it available based on
# a feature decoration
ifdef_wrap <- function(cpp11_wrapped, name, sexp_signature, decoration) {
  # if (identical(decoration, "arrow")) {
  #   # Arrow is now required
  #   return(cpp11_wrapped)
  # }
  glue('
  #if defined(ARROW_R_WITH_{toupper(decoration)})
  {cpp11_wrapped}
  #else
  extern "C" SEXP {sexp_signature}{{
  \tRf_error("Cannot call {name}(). See https://arrow.apache.org/docs/r/articles/install.html for help installing Arrow C++ libraries. ");
  }}
  #endif
  \n')
}

cpp_functions_definitions <- arrow_exports %>%
  select(name, return_type, args, file, line, decoration) %>%
  pmap_chr(function(name, return_type, args, file, line, decoration) {
    sexp_params <- glue_collapse_data(args, "SEXP {name}_sexp")
    sexp_signature <- glue('_arrow_{name}({sexp_params})')
    cpp11_wrapped <- glue('
      {return_type} {name}({real_params});
      extern "C" SEXP {sexp_signature}{{
      BEGIN_CPP11
      {input_params}{return_line}{wrap_call(name, return_type, args)}
      END_CPP11
      }}',
      sep = "\n",
      real_params = glue_collapse_data(args, "{type} {name}"),
      input_params = glue_collapse_data(args, "\tarrow::r::Input<{type}>::type {name}({name}_sexp);", sep = "\n"),
      return_line = if (nrow(args)) "\n" else "")

    glue::glue('
    // {basename(file)}
    {ifdef_wrap(cpp11_wrapped, name, sexp_signature, decoration)}
    ',
      sep = "\n",
    )
  }) %>%
  glue_collapse(sep = "\n")

cpp_functions_registration <- arrow_exports %>%
  select(name, return_type, args) %>%
  pmap_chr(function(name, return_type, args) {
    glue('\t\t{{ "_arrow_{name}", (DL_FUNC) &_arrow_{name}, {nrow(args)}}}, ')
  }) %>%
  glue_collapse(sep = "\n")

cpp_classes_finalizers <- map2(names(arrow_classes), arrow_classes, function(name, class) {
  sexp_signature <- glue('_arrow_{name}__Reset(SEXP r6)')
  cpp11_wrapped <- glue('
    extern "C" SEXP {sexp_signature} {{
    BEGIN_CPP11
    arrow::r::r6_reset_pointer<{class}>(r6);
    END_CPP11
    return R_NilValue;
    }}')
  ifdef_wrap(cpp11_wrapped, name, sexp_signature, "arrow")
}) %>%
  glue_collapse(sep = "\n")

classes_finalizers_registration <- glue('\t\t{{ "_arrow_{names(arrow_classes)}__Reset", (DL_FUNC) &_arrow_{names(arrow_classes)}__Reset, 1}}, ') %>%
  glue_collapse(sep = "\n")

cpp_file_header <- '// Generated by using data-raw/codegen.R -> do not edit by hand
#include <cpp11.hpp>
#include <cpp11/declarations.hpp>

#include "./arrow_types.h"
'

arrow_exports_cpp <- paste0(
glue::glue('
{cpp_file_header}
{cpp_functions_definitions}
{cpp_classes_finalizers}
\n'),
glue::glue_collapse(glue::glue('
{feature_available({features})}
'), sep = '\n'),
'
static const R_CallMethodDef CallEntries[] = {
',
glue::glue_collapse(glue::glue('
\t\t{{ "_{features}_available", (DL_FUNC)& _{features}_available, 0 }},
'), sep = '\n'),
glue::glue('\n
{cpp_functions_registration}
{classes_finalizers_registration}
\t\t{{NULL, NULL, 0}}
}};
\n'),
'extern "C" void R_init_arrow(DllInfo* dll){
  R_registerRoutines(dll, NULL, CallEntries, NULL, NULL);
  R_useDynamicSymbols(dll, FALSE);

  #if defined(ARROW_R_WITH_ARROW) && defined(HAS_ALTREP)
  arrow::r::altrep::Init_Altrep_classes(dll);
  #endif

}
\n')

write_if_modified(arrow_exports_cpp, "src/arrowExports.cpp")

r_functions <- arrow_exports %>%
  select(name, return_type, args) %>%
  pmap_chr(function(name, return_type, args) {
    params <- if (nrow(args)) {
      paste0(", ", glue_collapse_data(args, "{name}"))
    } else {
      ""
    }
    call <- glue::glue('.Call(`_arrow_{name}`{params})')
    if (return_type == "void") {
      call <- glue::glue('invisible({call})')
    }

    glue::glue('
    {name} <- function({list_params}) {{
      {call}
    }}

    ',
      list_params = glue_collapse_data(args, "{name}"),
      sep = "\n",
    )
  }) %>%
  glue_collapse(sep = "\n")

arrow_exports_r <- glue::glue('
# Generated by using data-raw/codegen.R -> do not edit by hand

{r_functions}
')

write_if_modified(arrow_exports_r, "R/arrowExports.R")