// Copyright (c) the JPEG XL Project Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

#include "lib/jxl/modular/encoding/dec_ma.h"

#include <jxl/memory_manager.h>

#include <algorithm>

#include <cstddef>

#include <cstdint>

#include <limits>

#include <utility>

#include <vector>

#include "lib/jxl/base/printf_macros.h"

#include "lib/jxl/base/status.h"

#include "lib/jxl/dec_ans.h"

#include "lib/jxl/dec_bit_reader.h"

#include "lib/jxl/modular/encoding/ma_common.h"

#include "lib/jxl/modular/modular_image.h"

#include "lib/jxl/modular/options.h"

#include "lib/jxl/pack_signed.h"

namespace jxl {

namespace {

enum class NextAction { CHECK_AND_GO_LEFT, GO_RIGHT, POP };

struct WorkItem {

  size_t node_index;

  pixel_type orig_l;

  pixel_type orig_u;

  NextAction action;

};

Status ValidateTree(const Tree& tree) {

  if (tree.empty()) return true;

  // TODO(eustas): or invalid?

  int num_properties = 0;

  for (auto node : tree) {

    if (node.property >= num_properties) {

      num_properties = node.property + 1;

    }

  }

  std::vector<std::pair<pixel_type, pixel_type>> property_ranges(

      num_properties);

  for (int i = 0; i < num_properties; i++) {

    property_ranges[i].first = std::numeric_limits<pixel_type>::min();

    property_ranges[i].second = std::numeric_limits<pixel_type>::max();

  }

  constexpr size_t kHeightLimit = 2048;

  std::vector<WorkItem> stack;

  stack.push_back({/*node_index=*/0, /*orig_l=*/0, /*orig_u=*/0,

                   NextAction::CHECK_AND_GO_LEFT});

  while (!stack.empty()) {

    if (stack.size() >= kHeightLimit) return JXL_FAILURE("Tree too tall");

    WorkItem& item = stack.back();

    const auto& node = tree[item.node_index];

    switch (item.action) {

      case NextAction::CHECK_AND_GO_LEFT: {

        int16_t p = node.property;

        if (p == -1) {

          stack.pop_back();

          continue;

        }

        PropertyVal v = node.splitval;

        pixel_type l = property_ranges[p].first;

        pixel_type u = property_ranges[p].second;

        if (l > v || u <= v) {

          return JXL_FAILURE("Invalid tree");

        }

        item.orig_l = l;

        item.orig_u = u;

        item.action = NextAction::GO_RIGHT;

        property_ranges[node.property].first = node.splitval + 1;

        stack.push_back({/*node_index=*/node.lchild,

                         /*orig_l=*/0, /*orig_u=*/0,

                         NextAction::CHECK_AND_GO_LEFT});

        continue;

      }

      case NextAction::GO_RIGHT:

        item.action = NextAction::POP;

        property_ranges[node.property].first = item.orig_l;

        property_ranges[node.property].second = node.splitval;

        stack.push_back({/*node_index=*/node.rchild,

                         /*orig_l=*/0, /*orig_u=*/0,

                         NextAction::CHECK_AND_GO_LEFT});

        continue;

      case NextAction::POP:

        property_ranges[node.property].second = item.orig_u;

        stack.pop_back();

        continue;

    }

  }

  return true;

}

Status DecodeTree(BitReader* br, ANSSymbolReader* reader,

                  const std::vector<uint8_t>& context_map, Tree* tree,

                  size_t tree_size_limit) {

  size_t leaf_id = 0;

  size_t to_decode = 1;

  tree->clear();

  while (to_decode > 0) {

    JXL_RETURN_IF_ERROR(br->AllReadsWithinBounds());

    if (tree->size() > tree_size_limit) {

      return JXL_FAILURE("Tree is too large: %" PRIuS " nodes vs %" PRIuS

                         " max nodes",

                         tree->size(), tree_size_limit);

    }

    to_decode--;

    uint32_t prop1 = reader->ReadHybridUint(kPropertyContext, br, context_map);

    if (prop1 > 256) return JXL_FAILURE("Invalid tree property value");

    int property = prop1 - 1;

    if (property == -1) {

      size_t predictor =

          reader->ReadHybridUint(kPredictorContext, br, context_map);

      if (predictor >= kNumModularPredictors) {

        return JXL_FAILURE("Invalid predictor");

      }

      int64_t predictor_offset =

          UnpackSigned(reader->ReadHybridUint(kOffsetContext, br, context_map));

      uint32_t mul_log =

          reader->ReadHybridUint(kMultiplierLogContext, br, context_map);

      if (mul_log >= 31) {

        return JXL_FAILURE("Invalid multiplier logarithm");

      }

      uint32_t mul_bits =

          reader->ReadHybridUint(kMultiplierBitsContext, br, context_map);

      if (mul_bits >= (1u << (31u - mul_log)) - 1u) {

        return JXL_FAILURE("Invalid multiplier");

      }

      uint32_t multiplier = (mul_bits + 1U) << mul_log;

      Predictor p = static_cast<Predictor>(static_cast<uint32_t>(predictor));

      tree->emplace_back(-1, 0, static_cast<int>(leaf_id), 0, p,

                         predictor_offset, multiplier);

      leaf_id++;

      continue;

    }

    int splitval =

        UnpackSigned(reader->ReadHybridUint(kSplitValContext, br, context_map));

    tree->emplace_back(

        property, splitval, static_cast<int>(tree->size() + to_decode + 1),

        static_cast<int>(tree->size() + to_decode + 2), Predictor::Zero, 0, 1);

    to_decode += 2;

  }

  return ValidateTree(*tree);

}

}  // namespace

Status DecodeTree(JxlMemoryManager* memory_manager, BitReader* br, Tree* tree,

                  size_t tree_size_limit) {

  std::vector<uint8_t> tree_context_map;

  ANSCode tree_code;

  JXL_RETURN_IF_ERROR(DecodeHistograms(memory_manager, br, kNumTreeContexts,

                                       &tree_code, &tree_context_map));

  // TODO(eustas): investigate more infinite tree cases.

  if (tree_code.degenerate_symbols[tree_context_map[kPropertyContext]] > 0) {

    return JXL_FAILURE("Infinite tree");

  }

  JXL_ASSIGN_OR_RETURN(ANSSymbolReader reader,

                       ANSSymbolReader::Create(&tree_code, br));

  JXL_RETURN_IF_ERROR(DecodeTree(br, &reader, tree_context_map, tree,

                                 std::min(tree_size_limit, kMaxTreeSize)));

  if (!reader.CheckANSFinalState()) {

    return JXL_FAILURE("ANS decode final state failed");

  }

  return true;

}

}  // namespace jxl