/* SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup obj
 */

#pragma once

#include <cstdio>
#include <string>
#include <type_traits>
#include <vector>

#include "BLI_compiler_attrs.h"
#include "BLI_fileops.h"
#include "BLI_string_ref.hh"
#include "BLI_utility_mixins.hh"

/* SEP macro from BLI path utils clashes with SEP symbol in fmt headers. */
#undef SEP
#define FMT_HEADER_ONLY
#include <fmt/format.h>

namespace blender::io::obj {

enum class eFileType {
  OBJ,
  MTL,
};

enum class eOBJSyntaxElement {
  vertex_coords,
  vertex_coords_color,
  uv_vertex_coords,
  normal,
  poly_element_begin,
  vertex_uv_normal_indices,
  vertex_normal_indices,
  vertex_uv_indices,
  vertex_indices,
  poly_element_end,
  poly_usemtl,
  edge,
  cstype,
  nurbs_degree,
  curve_element_begin,
  curve_element_end,
  nurbs_parameter_begin,
  nurbs_parameters,
  nurbs_parameter_end,
  nurbs_group_end,
  new_line,
  mtllib,
  smooth_group,
  object_group,
  object_name,
  /* Use rarely. New line is NOT included for string. */
  string,
};

enum class eMTLSyntaxElement {
  newmtl,
  Ni,
  d,
  Ns,
  illum,
  Ka,
  Kd,
  Ks,
  Ke,
  map_Kd,
  map_Ks,
  map_Ns,
  map_d,
  map_refl,
  map_Ke,
  map_Bump,
  /* Use rarely. New line is NOT included for string. */
  string,
};

template<eFileType filetype> struct FileTypeTraits;

/* Used to prevent mixing of say OBJ file format with MTL syntax elements. */
template<> struct FileTypeTraits<eFileType::OBJ> {
  using SyntaxType = eOBJSyntaxElement;
};

template<> struct FileTypeTraits<eFileType::MTL> {
  using SyntaxType = eMTLSyntaxElement;
};

struct FormattingSyntax {
  /* Formatting syntax with the file format key like `newmtl %s\n`. */
  const char *fmt = nullptr;
  /* Number of arguments needed by the syntax. */
  const int total_args = 0;
  /* Whether types of the given arguments are accepted by the syntax above. Fail to compile by
   * default.
   */
  const bool are_types_valid = false;
};

/**
 * Type dependent but always false. Use to add a `constexpr` conditional compile-time error.
 */
template<typename T> struct always_false : std::false_type {
};

template<typename... T>
constexpr bool is_type_float = (... && std::is_floating_point_v<std::decay_t<T>>);

template<typename... T>
constexpr bool is_type_integral = (... && std::is_integral_v<std::decay_t<T>>);

template<typename... T>
constexpr bool is_type_string_related = (... && std::is_constructible_v<std::string, T>);

/* GCC (at least 9.3) while compiling the obj_exporter_tests.cc with optimizations on,
 * results in "obj_export_io.hh:205:18: warning: ‘%s’ directive output truncated writing 34 bytes
 * into a region of size 6" and similar warnings. Yes the output is truncated, and that is covered
 * as an edge case by tests on purpose. */
#if defined(__GNUC__) && !defined(__clang__)
#  pragma GCC diagnostic push
#  pragma GCC diagnostic ignored "-Wformat-truncation"
#endif
template<typename... T>
constexpr FormattingSyntax syntax_elem_to_formatting(const eOBJSyntaxElement key)
{
  switch (key) {
    case eOBJSyntaxElement::vertex_coords: {
      return {"v {:.6f} {:.6f} {:.6f}\n", 3, is_type_float<T...>};
    }
    case eOBJSyntaxElement::vertex_coords_color: {
      return {"v {:.6f} {:.6f} {:.6f} {:.4f} {:.4f} {:.4f}\n", 6, is_type_float<T...>};
    }
    case eOBJSyntaxElement::uv_vertex_coords: {
      return {"vt {:.6f} {:.6f}\n", 2, is_type_float<T...>};
    }
    case eOBJSyntaxElement::normal: {
      return {"vn {:.4f} {:.4f} {:.4f}\n", 3, is_type_float<T...>};
    }
    case eOBJSyntaxElement::poly_element_begin: {
      return {"f", 0, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::vertex_uv_normal_indices: {
      return {" {}/{}/{}", 3, is_type_integral<T...>};
    }
    case eOBJSyntaxElement::vertex_normal_indices: {
      return {" {}//{}", 2, is_type_integral<T...>};
    }
    case eOBJSyntaxElement::vertex_uv_indices: {
      return {" {}/{}", 2, is_type_integral<T...>};
    }
    case eOBJSyntaxElement::vertex_indices: {
      return {" {}", 1, is_type_integral<T...>};
    }
    case eOBJSyntaxElement::poly_usemtl: {
      return {"usemtl {}\n", 1, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::edge: {
      return {"l {} {}\n", 2, is_type_integral<T...>};
    }
    case eOBJSyntaxElement::cstype: {
      return {"cstype bspline\n", 0, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::nurbs_degree: {
      return {"deg {}\n", 1, is_type_integral<T...>};
    }
    case eOBJSyntaxElement::curve_element_begin: {
      return {"curv 0.0 1.0", 0, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::nurbs_parameter_begin: {
      return {"parm u 0.0", 0, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::nurbs_parameters: {
      return {" {:.6f}", 1, is_type_float<T...>};
    }
    case eOBJSyntaxElement::nurbs_parameter_end: {
      return {" 1.0\n", 0, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::nurbs_group_end: {
      return {"end\n", 0, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::poly_element_end: {
      ATTR_FALLTHROUGH;
    }
    case eOBJSyntaxElement::curve_element_end: {
      ATTR_FALLTHROUGH;
    }
    case eOBJSyntaxElement::new_line: {
      return {"\n", 0, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::mtllib: {
      return {"mtllib {}\n", 1, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::smooth_group: {
      return {"s {}\n", 1, is_type_integral<T...>};
    }
    case eOBJSyntaxElement::object_group: {
      return {"g {}\n", 1, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::object_name: {
      return {"o {}\n", 1, is_type_string_related<T...>};
    }
    case eOBJSyntaxElement::string: {
      return {"{}", 1, is_type_string_related<T...>};
    }
  }
}

template<typename... T>
constexpr FormattingSyntax syntax_elem_to_formatting(const eMTLSyntaxElement key)
{
  switch (key) {
    case eMTLSyntaxElement::newmtl: {
      return {"newmtl {}\n", 1, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::Ni: {
      return {"Ni {:.6f}\n", 1, is_type_float<T...>};
    }
    case eMTLSyntaxElement::d: {
      return {"d {:.6f}\n", 1, is_type_float<T...>};
    }
    case eMTLSyntaxElement::Ns: {
      return {"Ns {:.6f}\n", 1, is_type_float<T...>};
    }
    case eMTLSyntaxElement::illum: {
      return {"illum {}\n", 1, is_type_integral<T...>};
    }
    case eMTLSyntaxElement::Ka: {
      return {"Ka {:.6f} {:.6f} {:.6f}\n", 3, is_type_float<T...>};
    }
    case eMTLSyntaxElement::Kd: {
      return {"Kd {:.6f} {:.6f} {:.6f}\n", 3, is_type_float<T...>};
    }
    case eMTLSyntaxElement::Ks: {
      return {"Ks {:.6f} {:.6f} {:.6f}\n", 3, is_type_float<T...>};
    }
    case eMTLSyntaxElement::Ke: {
      return {"Ke {:.6f} {:.6f} {:.6f}\n", 3, is_type_float<T...>};
    }
    /* NOTE: first texture map related argument, if present, will have its own leading space. */
    case eMTLSyntaxElement::map_Kd: {
      return {"map_Kd{} {}\n", 2, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::map_Ks: {
      return {"map_Ks{} {}\n", 2, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::map_Ns: {
      return {"map_Ns{} {}\n", 2, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::map_d: {
      return {"map_d{} {}\n", 2, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::map_refl: {
      return {"map_refl{} {}\n", 2, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::map_Ke: {
      return {"map_Ke{} {}\n", 2, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::map_Bump: {
      return {"map_Bump{} {}\n", 2, is_type_string_related<T...>};
    }
    case eMTLSyntaxElement::string: {
      return {"{}", 1, is_type_string_related<T...>};
    }
  }
}
#if defined(__GNUC__) && !defined(__clang__)
#  pragma GCC diagnostic pop
#endif

/**
 * File format and syntax agnostic file buffer writer.
 * All writes are done into an internal chunked memory buffer
 * (list of default 64 kilobyte blocks).
 * Call write_fo_file once in a while to write the memory buffer(s)
 * into the given file.
 */
template<eFileType filetype, size_t buffer_chunk_size = 64 * 1024>
class FormatHandler : NonCopyable, NonMovable {
 private:
  typedef std::vector<char> VectorChar;
  std::vector<VectorChar> blocks_;

 public:
  /* Write contents to the buffer(s) into a file, and clear the buffers. */
  void write_to_file(FILE *f)
  {
    for (const auto &b : blocks_)
      fwrite(b.data(), 1, b.size(), f);
    blocks_.clear();
  }

  std::string get_as_string() const
  {
    std::string s;
    for (const auto &b : blocks_)
      s.append(b.data(), b.size());
    return s;
  }
  size_t get_block_count() const
  {
    return blocks_.size();
  }

  void append_from(FormatHandler<filetype, buffer_chunk_size> &v)
  {
    blocks_.insert(blocks_.end(),
                   std::make_move_iterator(v.blocks_.begin()),
                   std::make_move_iterator(v.blocks_.end()));
    v.blocks_.clear();
  }

  /**
   * Example invocation: `writer->write<eMTLSyntaxElement::newmtl>("foo")`.
   *
   * \param key: Must match what the instance's filetype expects; i.e., `eMTLSyntaxElement` for
   * `eFileType::MTL`.
   */
  template<typename FileTypeTraits<filetype>::SyntaxType key, typename... T>
  constexpr void write(T &&...args)
  {
    /* Get format syntax, number of arguments expected and whether types of given arguments are
     * valid.
     */
    constexpr FormattingSyntax fmt_nargs_valid = syntax_elem_to_formatting<T...>(key);
    BLI_STATIC_ASSERT(fmt_nargs_valid.are_types_valid &&
                          (sizeof...(T) == fmt_nargs_valid.total_args),
                      "Types of all arguments and the number of arguments should match what the "
                      "formatting specifies.");
    write_impl(fmt_nargs_valid.fmt, std::forward<T>(args)...);
  }

 private:
  /* Ensure the last block contains at least this amount of free space.
   * If not, add a new block with max of block size & the amount of space needed. */
  void ensure_space(size_t at_least)
  {
    if (blocks_.empty() || (blocks_.back().capacity() - blocks_.back().size() < at_least)) {
      VectorChar &b = blocks_.emplace_back(VectorChar());
      b.reserve(std::max(at_least, buffer_chunk_size));
    }
  }

  template<typename... T> void write_impl(const char *fmt, T &&...args)
  {
    /* Format into a local buffer. */
    fmt::memory_buffer buf;
    fmt::format_to(fmt::appender(buf), fmt, std::forward<T>(args)...);
    size_t len = buf.size();
    ensure_space(len);
    VectorChar &bb = blocks_.back();
    bb.insert(bb.end(), buf.begin(), buf.end());
  }
};

}  // namespace blender::io::obj