// Copyright (c) 2011-2017 The OTS 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 "gsub.h"

#include <limits>

#include <vector>

#include "layout.h"

#include "maxp.h"

// GSUB - The Glyph Substitution Table

// http://www.microsoft.com/typography/otspec/gsub.htm

#define TABLE_NAME "GSUB"

namespace {

enum GSUB_TYPE {

  GSUB_TYPE_SINGLE = 1,

  GSUB_TYPE_MULTIPLE = 2,

  GSUB_TYPE_ALTERNATE = 3,

  GSUB_TYPE_LIGATURE = 4,

  GSUB_TYPE_CONTEXT = 5,

  GSUB_TYPE_CHANGING_CONTEXT = 6,

  GSUB_TYPE_EXTENSION_SUBSTITUTION = 7,

  GSUB_TYPE_REVERSE_CHAINING_CONTEXT_SINGLE = 8,

  GSUB_TYPE_RESERVED = 9

};

bool ParseSequenceTable(const ots::Font *font,

                        const uint8_t *data, const size_t length,

                        const uint16_t num_glyphs) {

  ots::Buffer subtable(data, length);

  uint16_t glyph_count = 0;

  if (!subtable.ReadU16(&glyph_count)) {

    return OTS_FAILURE_MSG("Failed to read glyph count in sequence table");

  }

  if (glyph_count > num_glyphs) {

    return OTS_FAILURE_MSG("bad glyph count %d > %d", glyph_count, num_glyphs);

  }

  for (unsigned i = 0; i < glyph_count; ++i) {

    uint16_t substitute = 0;

    if (!subtable.ReadU16(&substitute)) {

      return OTS_FAILURE_MSG("Failed to read substitution %d in sequence table", i);

    }

    if (substitute >= num_glyphs) {

      return OTS_FAILURE_MSG("Bad substitution (%d) %d > %d", i, substitute, num_glyphs);

    }

  }

  return true;

}

bool ParseAlternateSetTable(const ots::Font *font,

                            const uint8_t *data, const size_t length,

                            const uint16_t num_glyphs) {

  ots::Buffer subtable(data, length);

  uint16_t glyph_count = 0;

  if (!subtable.ReadU16(&glyph_count)) {

    return OTS_FAILURE_MSG("Failed to read alternate set header");

  }

  if (glyph_count > num_glyphs) {

    return OTS_FAILURE_MSG("Bad glyph count %d > %d in alternate set table", glyph_count, num_glyphs);

  }

  for (unsigned i = 0; i < glyph_count; ++i) {

    uint16_t alternate = 0;

    if (!subtable.ReadU16(&alternate)) {

      return OTS_FAILURE_MSG("Can't read alternate %d", i);

    }

    if (alternate >= num_glyphs) {

      return OTS_FAILURE_MSG("Too large alternate: %u", alternate);

    }

  }

  return true;

}

bool ParseLigatureTable(const ots::Font *font,

                        const uint8_t *data, const size_t length,

                        const uint16_t num_glyphs) {

  ots::Buffer subtable(data, length);

  uint16_t lig_glyph = 0;

  uint16_t comp_count = 0;

  if (!subtable.ReadU16(&lig_glyph) ||

      !subtable.ReadU16(&comp_count)) {

    return OTS_FAILURE_MSG("Failed to read ligature table header");

  }

  if (lig_glyph >= num_glyphs) {

    return OTS_FAILURE_MSG("too large lig_glyph: %u", lig_glyph);

  }

  if (comp_count == 0) {

    return OTS_FAILURE_MSG("Component count cannot be 0");

  }

  for (unsigned i = 0; i < comp_count - static_cast<unsigned>(1); ++i) {

    uint16_t component = 0;

    if (!subtable.ReadU16(&component)) {

      return OTS_FAILURE_MSG("Can't read ligature component %d", i);

    }

    if (component >= num_glyphs) {

      return OTS_FAILURE_MSG("Bad ligature component %d of %d", i, component);

    }

  }

  return true;

}

bool ParseLigatureSetTable(const ots::Font *font,

                           const uint8_t *data, const size_t length,

                           const uint16_t num_glyphs) {

  ots::Buffer subtable(data, length);

  uint16_t ligature_count = 0;

  if (!subtable.ReadU16(&ligature_count)) {

    return OTS_FAILURE_MSG("Can't read ligature count in ligature set");

  }

  const unsigned ligature_end = static_cast<unsigned>(2) + ligature_count * 2;

  if (ligature_end > std::numeric_limits<uint16_t>::max()) {

    return OTS_FAILURE_MSG("Bad end of ligature %d in ligature set", ligature_end);

  }

  for (unsigned i = 0; i < ligature_count; ++i) {

    uint16_t offset_ligature = 0;

    if (!subtable.ReadU16(&offset_ligature)) {

      return OTS_FAILURE_MSG("Failed to read ligature offset %d", i);

    }

    if (offset_ligature < ligature_end || offset_ligature >= length) {

      return OTS_FAILURE_MSG("Bad ligature offset %d for ligature %d", offset_ligature, i);

    }

    if (!ParseLigatureTable(font, data + offset_ligature, length - offset_ligature,

                            num_glyphs)) {

      return OTS_FAILURE_MSG("Failed to parse ligature %d", i);

    }

  }

  return true;

}

}  // namespace

namespace ots {

// Lookup Type 1:

// Single Substitution Subtable

bool OpenTypeGSUB::ParseSingleSubstitution(const uint8_t *data,

                                           const size_t length) {

  Font* font = GetFont();

  Buffer subtable(data, length);

  uint16_t format = 0;

  uint16_t offset_coverage = 0;

  if (!subtable.ReadU16(&format) ||

      !subtable.ReadU16(&offset_coverage)) {

    return Error("Failed to read single subst table header");

  }

  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(

      font->GetTypedTable(OTS_TAG_MAXP));

  if (!maxp) {

    return Error("Required maxp table missing");

  }

  const uint16_t num_glyphs = maxp->num_glyphs;

  if (format == 1) {

    // Parse SingleSubstFormat1

    int16_t delta_glyph_id = 0;

    if (!subtable.ReadS16(&delta_glyph_id)) {

      return Error("Failed to read glyph shift from format 1 single subst table");

    }

    if (std::abs(delta_glyph_id) >= num_glyphs) {

      return Error("bad glyph shift of %d in format 1 single subst table", delta_glyph_id);

    }

  } else if (format == 2) {

    // Parse SingleSubstFormat2

    uint16_t glyph_count = 0;

    if (!subtable.ReadU16(&glyph_count)) {

      return Error("Failed to read glyph cound in format 2 single subst table");

    }

    if (glyph_count > num_glyphs) {

      return Error("Bad glyph count %d > %d in format 2 single subst table", glyph_count, num_glyphs);

    }

    for (unsigned i = 0; i < glyph_count; ++i) {

      uint16_t substitute = 0;

      if (!subtable.ReadU16(&substitute)) {

        return Error("Failed to read substitution %d in format 2 single subst table", i);

      }

      if (substitute >= num_glyphs) {

        return Error("too large substitute: %u", substitute);

      }

    }

  } else {

    return Error("Bad single subst table format %d", format);

  }

  if (offset_coverage < subtable.offset() || offset_coverage >= length) {

    return Error("Bad coverage offset %x", offset_coverage);

  }

  if (!ots::ParseCoverageTable(font, data + offset_coverage,

                               length - offset_coverage, num_glyphs)) {

    return Error("Failed to parse coverage table");

  }

  return true;

}

// Lookup Type 2:

// Multiple Substitution Subtable

bool OpenTypeGSUB::ParseMutipleSubstitution(const uint8_t *data,

                                            const size_t length) {

  Font* font = GetFont();

  Buffer subtable(data, length);

  uint16_t format = 0;

  uint16_t offset_coverage = 0;

  uint16_t sequence_count = 0;

  if (!subtable.ReadU16(&format) ||

      !subtable.ReadU16(&offset_coverage) ||

      !subtable.ReadU16(&sequence_count)) {

    return Error("Can't read header of multiple subst table");

  }

  if (format != 1) {

    return Error("Bad multiple subst table format %d", format);

  }

  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(

      font->GetTypedTable(OTS_TAG_MAXP));

  if (!maxp) {

    return Error("Required maxp table missing");

  }

  const uint16_t num_glyphs = maxp->num_glyphs;

  const unsigned sequence_end = static_cast<unsigned>(6) +

      sequence_count * 2;

  if (sequence_end > std::numeric_limits<uint16_t>::max()) {

    return Error("Bad sequence end %d, in multiple subst", sequence_end);

  }

  for (unsigned i = 0; i < sequence_count; ++i) {

    uint16_t offset_sequence = 0;

    if (!subtable.ReadU16(&offset_sequence)) {

      return Error("Failed to read sequence offset for sequence %d", i);

    }

    if (offset_sequence < sequence_end || offset_sequence >= length) {

      return Error("Bad sequence offset %d for sequence %d", offset_sequence, i);

    }

    if (!ParseSequenceTable(font, data + offset_sequence, length - offset_sequence,

                            num_glyphs)) {

      return Error("Failed to parse sequence table %d", i);

    }

  }

  if (offset_coverage < sequence_end || offset_coverage >= length) {

    return Error("Bad coverage offset %d", offset_coverage);

  }

  if (!ots::ParseCoverageTable(font, data + offset_coverage,

                               length - offset_coverage, num_glyphs)) {

    return Error("Failed to parse coverage table");

  }

  return true;

}

// Lookup Type 3:

// Alternate Substitution Subtable

bool OpenTypeGSUB::ParseAlternateSubstitution(const uint8_t *data,

                                              const size_t length) {

  Font* font = GetFont();

  Buffer subtable(data, length);

  uint16_t format = 0;

  uint16_t offset_coverage = 0;

  uint16_t alternate_set_count = 0;

  if (!subtable.ReadU16(&format) ||

      !subtable.ReadU16(&offset_coverage) ||

      !subtable.ReadU16(&alternate_set_count)) {

    return Error("Can't read alternate subst header");

  }

  if (format != 1) {

    return Error("Bad alternate subst table format %d", format);

  }

  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(

      font->GetTypedTable(OTS_TAG_MAXP));

  if (!maxp) {

    return Error("Required maxp table missing");

  }

  const uint16_t num_glyphs = maxp->num_glyphs;

  const unsigned alternate_set_end = static_cast<unsigned>(6) +

      alternate_set_count * 2;

  if (alternate_set_end > std::numeric_limits<uint16_t>::max()) {

    return Error("Bad end of alternate set %d", alternate_set_end);

  }

  for (unsigned i = 0; i < alternate_set_count; ++i) {

    uint16_t offset_alternate_set = 0;

    if (!subtable.ReadU16(&offset_alternate_set)) {

      return Error("Can't read alternate set offset for set %d", i);

    }

    if (offset_alternate_set < alternate_set_end ||

        offset_alternate_set >= length) {

      return Error("Bad alternate set offset %d for set %d", offset_alternate_set, i);

    }

    if (!ParseAlternateSetTable(font, data + offset_alternate_set,

                                length - offset_alternate_set,

                                num_glyphs)) {

      return Error("Failed to parse alternate set");

    }

  }

  if (offset_coverage < alternate_set_end || offset_coverage >= length) {

    return Error("Bad coverage offset %d", offset_coverage);

  }

  if (!ots::ParseCoverageTable(font, data + offset_coverage,

                               length - offset_coverage, num_glyphs)) {

    return Error("Failed to parse coverage table");

  }

  return true;

}

// Lookup Type 4:

// Ligature Substitution Subtable

bool OpenTypeGSUB::ParseLigatureSubstitution(const uint8_t *data,

                                             const size_t length) {

  Font* font = GetFont();

  Buffer subtable(data, length);

  uint16_t format = 0;

  uint16_t offset_coverage = 0;

  uint16_t lig_set_count = 0;

  if (!subtable.ReadU16(&format) ||

      !subtable.ReadU16(&offset_coverage) ||

      !subtable.ReadU16(&lig_set_count)) {

    return Error("Failed to read ligature substitution header");

  }

  if (format != 1) {

    return Error("Bad ligature substitution table format %d", format);

  }

  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(

      font->GetTypedTable(OTS_TAG_MAXP));

  if (!maxp) {

    return Error("Required maxp table missing");

  }

  const uint16_t num_glyphs = maxp->num_glyphs;

  const unsigned ligature_set_end = static_cast<unsigned>(6) +

      lig_set_count * 2;

  if (ligature_set_end > std::numeric_limits<uint16_t>::max()) {

    return Error("Bad end of ligature set %d in ligature substitution table", ligature_set_end);

  }

  for (unsigned i = 0; i < lig_set_count; ++i) {

    uint16_t offset_ligature_set = 0;

    if (!subtable.ReadU16(&offset_ligature_set)) {

      return Error("Can't read ligature set offset %d", i);

    }

    if (offset_ligature_set < ligature_set_end ||

        offset_ligature_set >= length) {

      return Error("Bad ligature set offset %d for set %d", offset_ligature_set, i);

    }

    if (!ParseLigatureSetTable(font, data + offset_ligature_set,

                               length - offset_ligature_set, num_glyphs)) {

      return Error("Failed to parse ligature set %d", i);

    }

  }

  if (offset_coverage < ligature_set_end || offset_coverage >= length) {

    return Error("Bad coverage offset %d", offset_coverage);

  }

  if (!ots::ParseCoverageTable(font, data + offset_coverage,

                               length - offset_coverage, num_glyphs)) {

    return Error("Failed to parse coverage table");

  }

  return true;

}

// Lookup Type 5:

// Contextual Substitution Subtable

// OpenTypeLayoutTable::ParseContextSubtable()

// Lookup Type 6:

// Chaining Contextual Substitution Subtable

// OpenTypeLayoutTable::ParseChainingContextSubtable

// Lookup Type 7:

// Extension Substition

// OpenTypeLayoutTable::ParseExtensionSubtable

// Lookup Type 8:

// Reverse Chaining Contexual Single Substitution Subtable

bool OpenTypeGSUB::ParseReverseChainingContextSingleSubstitution(const uint8_t *data,

                                                                 const size_t length) {

  Font* font = GetFont();

  Buffer subtable(data, length);

  uint16_t format = 0;

  uint16_t offset_coverage = 0;

  if (!subtable.ReadU16(&format) ||

      !subtable.ReadU16(&offset_coverage)) {

    return Error("Failed to read reverse chaining header");

  }

  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(

      font->GetTypedTable(OTS_TAG_MAXP));

  if (!maxp) {

    return Error("Required maxp table missing");

  }

  const uint16_t num_glyphs = maxp->num_glyphs;

  uint16_t backtrack_glyph_count = 0;

  if (!subtable.ReadU16(&backtrack_glyph_count)) {

    return Error("Failed to read backtrack glyph count in reverse chaining table");

  }

  std::vector<uint16_t> offsets_backtrack;

  offsets_backtrack.reserve(backtrack_glyph_count);

  for (unsigned i = 0; i < backtrack_glyph_count; ++i) {

    uint16_t offset = 0;

    if (!subtable.ReadU16(&offset)) {

      return Error("Failed to read backtrack offset %d", i);

    }

    offsets_backtrack.push_back(offset);

  }

  uint16_t lookahead_glyph_count = 0;

  if (!subtable.ReadU16(&lookahead_glyph_count)) {

    return Error("Failed to read look ahead glyph count");

  }

  std::vector<uint16_t> offsets_lookahead;

  offsets_lookahead.reserve(lookahead_glyph_count);

  for (unsigned i = 0; i < lookahead_glyph_count; ++i) {

    uint16_t offset = 0;

    if (!subtable.ReadU16(&offset)) {

      return Error("Can't read look ahead offset %d", i);

    }

    offsets_lookahead.push_back(offset);

  }

  uint16_t glyph_count = 0;

  if (!subtable.ReadU16(&glyph_count)) {

    return Error("Can't read glyph count in reverse chaining table");

  }

  for (unsigned i = 0; i < glyph_count; ++i) {

    uint16_t substitute = 0;

    if (!subtable.ReadU16(&substitute)) {

      return Error("Failed to read substitution %d reverse chaining table", i);

    }

    if (substitute >= num_glyphs) {

      return Error("Bad substitute glyph %d in reverse chaining table substitution %d", substitute, i);

    }

  }

  const unsigned substitute_end = static_cast<unsigned>(10) +

      (backtrack_glyph_count + lookahead_glyph_count + glyph_count) * 2;

  if (substitute_end > std::numeric_limits<uint16_t>::max()) {

    return Error("Bad substitute end offset in reverse chaining table");

  }

  if (offset_coverage < substitute_end || offset_coverage >= length) {

    return Error("Bad coverage offset %d in reverse chaining table", offset_coverage);

  }

  if (!ots::ParseCoverageTable(font, data + offset_coverage,

                               length - offset_coverage, num_glyphs)) {

    return Error("Failed to parse coverage table in reverse chaining table");

  }

  for (unsigned i = 0; i < backtrack_glyph_count; ++i) {

    if (offsets_backtrack[i] < substitute_end ||

        offsets_backtrack[i] >= length) {

      return Error("Bad backtrack offset %d for backtrack %d in reverse chaining table", offsets_backtrack[i], i);

    }

    if (!ots::ParseCoverageTable(font, data + offsets_backtrack[i],

                                 length - offsets_backtrack[i], num_glyphs)) {

      return Error("Failed to parse coverage table for backtrack %d in reverse chaining table", i);

    }

  }

  for (unsigned i = 0; i < lookahead_glyph_count; ++i) {

    if (offsets_lookahead[i] < substitute_end ||

        offsets_lookahead[i] >= length) {

      return Error("Bad lookahead offset %d for lookahead %d in reverse chaining table", offsets_lookahead[i], i);

    }

    if (!ots::ParseCoverageTable(font, data + offsets_lookahead[i],

                                 length - offsets_lookahead[i], num_glyphs)) {

      return Error("Failed to parse lookahead coverage table %d in reverse chaining table", i);

    }

  }

  return true;

}

bool OpenTypeGSUB::ValidLookupSubtableType(const uint16_t lookup_type,

                                           bool extension) const {

  if (extension && lookup_type == GSUB_TYPE_EXTENSION_SUBSTITUTION)

    return false;

  return lookup_type >= GSUB_TYPE_SINGLE && lookup_type < GSUB_TYPE_RESERVED;

}

bool OpenTypeGSUB::ParseLookupSubtable(const uint8_t *data, const size_t length,

                                       const uint16_t lookup_type) {

  switch (lookup_type) {

    case GSUB_TYPE_SINGLE:

      return ParseSingleSubstitution(data, length);

    case GSUB_TYPE_MULTIPLE:

      return ParseMutipleSubstitution(data, length);

    case GSUB_TYPE_ALTERNATE:

      return ParseAlternateSubstitution(data, length);

    case GSUB_TYPE_LIGATURE:

      return ParseLigatureSubstitution(data, length);

    case GSUB_TYPE_CONTEXT:

      return ParseContextSubtable(data, length);

    case GSUB_TYPE_CHANGING_CONTEXT:

      return ParseChainingContextSubtable(data, length);

    case GSUB_TYPE_EXTENSION_SUBSTITUTION:

      return ParseExtensionSubtable(data, length);

    case GSUB_TYPE_REVERSE_CHAINING_CONTEXT_SINGLE:

      return ParseReverseChainingContextSingleSubstitution(data, length);

  }

  return false;

}

}  // namespace ots

#undef TABLE_NAME