#include "lex_utils.h"

#include <doctest/doctest.h>

#include <algorithm>

// VSCode (UTF-16) disagrees with Emacs lsp-mode (UTF-8) on how to represent
// text documents.
// We use a UTF-8 iterator to approximate UTF-16 in the specification (weird).
// This is good enough and fails only for UTF-16 surrogate pairs.
int GetOffsetForPosition(lsPosition position, std::string_view content) {
  size_t i = 0;
  for (; position.line > 0 && i < content.size(); i++)
    if (content[i] == '\n')
      position.line--;
  for (; position.character > 0 && i < content.size(); position.character--)
    if (uint8_t(content[i++]) >= 128) {
      // Skip 0b10xxxxxx
      while (i < content.size() && uint8_t(content[i]) >= 128 &&
             uint8_t(content[i]) < 192)
        i++;
    }
  return int(i);
}

lsPosition CharPos(std::string_view search,
                   char character,
                   int character_offset) {
  lsPosition result;
  int index = 0;
  while (index < search.size()) {
    char c = search[index];
    if (c == character)
      break;
    if (c == '\n') {
      result.line += 1;
      result.character = 0;
    } else {
      result.character += 1;
    }
    ++index;
  }
  assert(index < search.size());
  result.character += character_offset;
  return result;
}

ParseIncludeLineResult ParseIncludeLine(const std::string& line) {
  static const std::regex pattern(
      "(\\s*)"        // [1]: spaces before '#'
      "#"             //
      "(\\s*)"        // [2]: spaces after '#'
      "([^\\s\"<]*)"  // [3]: "include"
      "(\\s*)"        // [4]: spaces before quote
      "([\"<])?"      // [5]: the first quote char
      "([^\\s\">]*)"  // [6]: path of file
      "[\">]?"        //
      "(.*)");        // [7]: suffix after quote char
  std::smatch match;
  bool ok = std::regex_match(line, match, pattern);
  std::string text = match[3].str() + match[6].str();
  return {ok, text, match};
}

void DecorateIncludePaths(const std::smatch& match,
                          std::vector<lsCompletionItem>* items) {
  std::string spaces_after_include = " ";
  if (match[3].compare("include") == 0 && match[5].length())
    spaces_after_include = match[4].str();

  std::string prefix =
      match[1].str() + '#' + match[2].str() + "include" + spaces_after_include;
  std::string suffix = match[7].str();

  for (lsCompletionItem& item : *items) {
    char quote0, quote1;
    if (match[5].compare("<") == 0 ||
        (match[5].length() == 0 && item.use_angle_brackets_))
      quote0 = '<', quote1 = '>';
    else
      quote0 = quote1 = '"';

    item.textEdit->newText =
        prefix + quote0 + item.textEdit->newText + quote1 + suffix;
    item.label = prefix + quote0 + item.label + quote1 + suffix;
    item.filterText = nullopt;
  }
}

// TODO: eliminate |line_number| param.
optional<lsRange> ExtractQuotedRange(int line_number, const std::string& line) {
  // Find starting and ending quote.
  int start = 0;
  while (start < line.size()) {
    char c = line[start];
    ++start;
    if (c == '"' || c == '<')
      break;
  }
  if (start == line.size())
    return nullopt;

  int end = (int)line.size();
  while (end > 0) {
    char c = line[end];
    if (c == '"' || c == '>')
      break;
    --end;
  }

  if (start >= end)
    return nullopt;

  return lsRange(lsPosition(line_number, start), lsPosition(line_number, end));
}

void LexFunctionDeclaration(const std::string& buffer_content,
                            lsPosition declaration_spelling,
                            optional<std::string> type_name,
                            std::string* insert_text,
                            int* newlines_after_name) {
  int name_start = GetOffsetForPosition(declaration_spelling, buffer_content);

  bool parse_return_type = true;
  // We need to check if we have a return type (ctors and dtors do not).
  if (type_name) {
    int name_end = name_start;
    while (name_end < buffer_content.size()) {
      char c = buffer_content[name_end];
      if (isspace(c) || c == '(')
        break;
      ++name_end;
    }

    std::string func_name =
        buffer_content.substr(name_start, name_end - name_start);
    if (func_name == *type_name || func_name == ("~" + *type_name))
      parse_return_type = false;
  }

  // We need to fetch the return type. This can get complex, ie,
  //
  //  std::vector <int> foo();
  //
  int return_start = name_start;
  if (parse_return_type) {
    int paren_balance = 0;
    int angle_balance = 0;
    bool expect_token = true;
    while (return_start > 0) {
      char c = buffer_content[return_start - 1];
      if (paren_balance == 0 && angle_balance == 0) {
        if (isspace(c) && !expect_token) {
          break;
        }
        if (!isspace(c))
          expect_token = false;
      }

      if (c == ')')
        ++paren_balance;
      if (c == '(') {
        --paren_balance;
        expect_token = true;
      }

      if (c == '>')
        ++angle_balance;
      if (c == '<') {
        --angle_balance;
        expect_token = true;
      }

      return_start -= 1;
    }
  }

  // We need to fetch the arguments. Just scan for the next ';'.
  *newlines_after_name = 0;
  int end = name_start;
  while (end < buffer_content.size()) {
    char c = buffer_content[end];
    if (c == ';')
      break;
    if (c == '\n')
      *newlines_after_name += 1;
    ++end;
  }

  std::string result;
  result += buffer_content.substr(return_start, name_start - return_start);
  if (type_name && !type_name->empty())
    result += *type_name + "::";
  result += buffer_content.substr(name_start, end - name_start);
  TrimEndInPlace(result);
  result += " {\n}";
  *insert_text = result;
}

std::string LexWordAroundPos(lsPosition position, const std::string& content) {
  int index = GetOffsetForPosition(position, content);

  int start = index;
  int end = index;

  while (start > 0) {
    char c = content[start - 1];
    if (isalnum(c) || c == '_') {
      --start;
    } else {
      break;
    }
  }

  while ((end + 1) < content.size()) {
    char c = content[end + 1];
    if (isalnum(c) || c == '_') {
      ++end;
    } else {
      break;
    }
  }

  return content.substr(start, end - start + 1);
}

bool SubsequenceMatch(std::string_view search, std::string_view content) {
  size_t j = 0;
  for (size_t i = 0; i < search.size(); i++) {
    char search_char = tolower(search[i]);
    while (j < content.size() && tolower(content[j]) != search_char)
      j++;
    if (j == content.size())
      return false;
    j++;
  }
  return true;
}

// Find discontinous |search| in |content|.
// Return |found| and the count of skipped chars before found.
std::tuple<bool, int> SubsequenceCountSkip(std::string_view search,
                                           std::string_view content) {
  bool hasUppercaseLetter = std::any_of(search.begin(), search.end(), isupper);
  int skip = 0;
  size_t j = 0;
  for (char c : search) {
    while (j < content.size() &&
           (hasUppercaseLetter ? content[j] != c
                               : tolower(content[j]) != tolower(c)))
      ++j, ++skip;
    if (j == content.size())
      return std::make_tuple(false, skip);
    ++j;
  }
  return std::make_tuple(true, skip);
}

TEST_SUITE("Offset") {
  TEST_CASE("past end") {
    std::string content = "foo";
    int offset = GetOffsetForPosition(lsPosition(10, 10), content);
    REQUIRE(offset <= content.size());
  }

  TEST_CASE("in middle of content") {
    std::string content = "abcdefghijk";
    for (int i = 0; i < content.size(); ++i) {
      int offset = GetOffsetForPosition(lsPosition(0, i), content);
      REQUIRE(i == offset);
    }
  }

  TEST_CASE("at end of content") {
    REQUIRE(GetOffsetForPosition(lsPosition(0, 0), "") == 0);
    REQUIRE(GetOffsetForPosition(lsPosition(0, 1), "a") == 1);
  }
}

TEST_SUITE("Substring") {
  TEST_CASE("match") {
    // Sanity.
    REQUIRE(SubsequenceMatch("a", "aa"));
    REQUIRE(SubsequenceMatch("aa", "aa"));

    // Empty string matches anything.
    REQUIRE(SubsequenceMatch("", ""));
    REQUIRE(SubsequenceMatch("", "aa"));

    // Match in start/middle/end.
    REQUIRE(SubsequenceMatch("a", "abbbb"));
    REQUIRE(SubsequenceMatch("a", "bbabb"));
    REQUIRE(SubsequenceMatch("a", "bbbba"));
    REQUIRE(SubsequenceMatch("aa", "aabbb"));
    REQUIRE(SubsequenceMatch("aa", "bbaab"));
    REQUIRE(SubsequenceMatch("aa", "bbbaa"));

    // Capitalization.
    REQUIRE(SubsequenceMatch("aa", "aA"));
    REQUIRE(SubsequenceMatch("aa", "Aa"));
    REQUIRE(SubsequenceMatch("aa", "AA"));

    // Token skipping.
    REQUIRE(SubsequenceMatch("ad", "abcd"));
    REQUIRE(SubsequenceMatch("ad", "ABCD"));

    // Ordering.
    REQUIRE(!SubsequenceMatch("ad", "dcba"));
  }

  TEST_CASE("skip") {
    REQUIRE(SubsequenceCountSkip("a", "a") == std::make_tuple(true, 0));
    REQUIRE(SubsequenceCountSkip("b", "a") == std::make_tuple(false, 1));
    REQUIRE(SubsequenceCountSkip("", "") == std::make_tuple(true, 0));
    REQUIRE(SubsequenceCountSkip("a", "ba") == std::make_tuple(true, 1));
    REQUIRE(SubsequenceCountSkip("aa", "aba") == std::make_tuple(true, 1));
    REQUIRE(SubsequenceCountSkip("aa", "baa") == std::make_tuple(true, 1));
    REQUIRE(SubsequenceCountSkip("aA", "aA") == std::make_tuple(true, 0));
    REQUIRE(SubsequenceCountSkip("aA", "aa") == std::make_tuple(false, 1));
    REQUIRE(SubsequenceCountSkip("incstdioh", "include <stdio.h>") == std::make_tuple(true, 7));
  }
}

TEST_SUITE("LexFunctionDeclaration") {
  TEST_CASE("simple") {
    std::string buffer_content = " void Foo(); ";
    lsPosition declaration = CharPos(buffer_content, 'F');
    std::string insert_text;
    int newlines_after_name = 0;

    LexFunctionDeclaration(buffer_content, declaration, nullopt, &insert_text,
                           &newlines_after_name);
    REQUIRE(insert_text == "void Foo() {\n}");
    REQUIRE(newlines_after_name == 0);

    LexFunctionDeclaration(buffer_content, declaration, std::string("Type"),
                           &insert_text, &newlines_after_name);
    REQUIRE(insert_text == "void Type::Foo() {\n}");
    REQUIRE(newlines_after_name == 0);
  }

  TEST_CASE("ctor") {
    std::string buffer_content = " Foo(); ";
    lsPosition declaration = CharPos(buffer_content, 'F');
    std::string insert_text;
    int newlines_after_name = 0;

    LexFunctionDeclaration(buffer_content, declaration, std::string("Foo"),
                           &insert_text, &newlines_after_name);
    REQUIRE(insert_text == "Foo::Foo() {\n}");
    REQUIRE(newlines_after_name == 0);
  }

  TEST_CASE("dtor") {
    std::string buffer_content = " ~Foo(); ";
    lsPosition declaration = CharPos(buffer_content, '~');
    std::string insert_text;
    int newlines_after_name = 0;

    LexFunctionDeclaration(buffer_content, declaration, std::string("Foo"),
                           &insert_text, &newlines_after_name);
    REQUIRE(insert_text == "Foo::~Foo() {\n}");
    REQUIRE(newlines_after_name == 0);
  }

  TEST_CASE("complex return type") {
    std::string buffer_content = " std::vector<int> Foo(); ";
    lsPosition declaration = CharPos(buffer_content, 'F');
    std::string insert_text;
    int newlines_after_name = 0;

    LexFunctionDeclaration(buffer_content, declaration, nullopt, &insert_text,
                           &newlines_after_name);
    REQUIRE(insert_text == "std::vector<int> Foo() {\n}");
    REQUIRE(newlines_after_name == 0);

    LexFunctionDeclaration(buffer_content, declaration, std::string("Type"),
                           &insert_text, &newlines_after_name);
    REQUIRE(insert_text == "std::vector<int> Type::Foo() {\n}");
    REQUIRE(newlines_after_name == 0);
  }

  TEST_CASE("extra complex return type") {
    std::string buffer_content = " std::function < int() > \n Foo(); ";
    lsPosition declaration = CharPos(buffer_content, 'F');
    std::string insert_text;
    int newlines_after_name = 0;

    LexFunctionDeclaration(buffer_content, declaration, nullopt, &insert_text,
                           &newlines_after_name);
    REQUIRE(insert_text == "std::function < int() > \n Foo() {\n}");
    REQUIRE(newlines_after_name == 0);

    LexFunctionDeclaration(buffer_content, declaration, std::string("Type"),
                           &insert_text, &newlines_after_name);
    REQUIRE(insert_text == "std::function < int() > \n Type::Foo() {\n}");
    REQUIRE(newlines_after_name == 0);
  }

  TEST_CASE("parameters") {
    std::string buffer_content = "void Foo(int a,\n\n    int b); ";
    lsPosition declaration = CharPos(buffer_content, 'F');
    std::string insert_text;
    int newlines_after_name = 0;

    LexFunctionDeclaration(buffer_content, declaration, nullopt, &insert_text,
                           &newlines_after_name);
    REQUIRE(insert_text == "void Foo(int a,\n\n    int b) {\n}");
    REQUIRE(newlines_after_name == 2);

    LexFunctionDeclaration(buffer_content, declaration, std::string("Type"),
                           &insert_text, &newlines_after_name);
    REQUIRE(insert_text == "void Type::Foo(int a,\n\n    int b) {\n}");
    REQUIRE(newlines_after_name == 2);
  }
}

TEST_SUITE("LexWordAroundPos") {
  TEST_CASE("edges") {
    std::string content = "Foobar";
    REQUIRE(LexWordAroundPos(CharPos(content, 'F'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'o'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'b'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'a'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'r'), content) == "Foobar");
  }

  TEST_CASE("simple") {
    std::string content = "  Foobar  ";
    REQUIRE(LexWordAroundPos(CharPos(content, 'F'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'o'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'b'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'a'), content) == "Foobar");
    REQUIRE(LexWordAroundPos(CharPos(content, 'r'), content) == "Foobar");
  }

  TEST_CASE("underscores and numbers") {
    std::string content = "  _my_t5ype7  ";
    REQUIRE(LexWordAroundPos(CharPos(content, '_'), content) == "_my_t5ype7");
    REQUIRE(LexWordAroundPos(CharPos(content, '5'), content) == "_my_t5ype7");
    REQUIRE(LexWordAroundPos(CharPos(content, 'e'), content) == "_my_t5ype7");
    REQUIRE(LexWordAroundPos(CharPos(content, '7'), content) == "_my_t5ype7");
  }

  TEST_CASE("dot, dash, colon are skipped") {
    std::string content = "1. 2- 3:";
    REQUIRE(LexWordAroundPos(CharPos(content, '1'), content) == "1");
    REQUIRE(LexWordAroundPos(CharPos(content, '2'), content) == "2");
    REQUIRE(LexWordAroundPos(CharPos(content, '3'), content) == "3");
  }
}