/*
 * Copyright (c) 2021, Itamar S. <itamar8910@gmail.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "Preprocessor.h"
#include <AK/Assertions.h>
#include <AK/GenericLexer.h>
#include <AK/StringBuilder.h>
#include <ctype.h>

namespace Cpp {
Preprocessor::Preprocessor(const String& filename, const StringView& program)
    : m_filename(filename)
    , m_program(program)
{
    m_lines = m_program.split_view('\n', true);
}

const String& Preprocessor::process()
{
    for (; m_line_index < m_lines.size(); ++m_line_index) {
        auto& line = m_lines[m_line_index];
        if (line.starts_with("#")) {
            handle_preprocessor_line(line);
        } else if (m_state == State::Normal) {
            m_builder.append(line);
        }
        m_builder.append("\n");
    }

    m_processed_text = m_builder.to_string();
    return m_processed_text;
}

void Preprocessor::handle_preprocessor_line(const StringView& line)
{
    GenericLexer lexer(line);

    auto consume_whitespace = [&] {
        lexer.ignore_while([](char ch) { return isspace(ch); });
        if (lexer.peek() == '/' && lexer.peek(1) == '/')
            lexer.ignore_until([](char ch) { return ch == '\n'; });
    };

    consume_whitespace();
    lexer.consume_specific('#');
    consume_whitespace();
    auto keyword = lexer.consume_until(' ');
    if (keyword.is_empty() || keyword.is_null() || keyword.is_whitespace())
        return;

    if (keyword == "include") {
        consume_whitespace();
        m_included_paths.append(lexer.consume_all());
        return;
    }

    if (keyword == "else") {
        VERIFY(m_current_depth > 0);
        if (m_depths_of_not_taken_branches.contains_slow(m_current_depth - 1)) {
            m_depths_of_not_taken_branches.remove_all_matching([this](auto x) { return x == m_current_depth - 1; });
            m_state = State::Normal;
        }
        if (m_depths_of_taken_branches.contains_slow(m_current_depth - 1)) {
            m_state = State::SkipElseBranch;
        }
        return;
    }

    if (keyword == "endif") {
        VERIFY(m_current_depth > 0);
        --m_current_depth;
        if (m_depths_of_not_taken_branches.contains_slow(m_current_depth)) {
            m_depths_of_not_taken_branches.remove_all_matching([this](auto x) { return x == m_current_depth; });
        }
        if (m_depths_of_taken_branches.contains_slow(m_current_depth)) {
            m_depths_of_taken_branches.remove_all_matching([this](auto x) { return x == m_current_depth; });
        }
        m_state = State::Normal;
        return;
    }

    if (keyword == "define") {
        if (m_state == State::Normal) {
            auto key = lexer.consume_until(' ');
            consume_whitespace();

            DefinedValue value;
            value.filename = m_filename;
            value.line = m_line_index;

            auto string_value = lexer.consume_all();
            if (!string_value.is_empty())
                value.value = string_value;

            m_definitions.set(key, value);
        }
        return;
    }
    if (keyword == "undef") {
        if (m_state == State::Normal) {
            auto key = lexer.consume_until(' ');
            lexer.consume_all();
            m_definitions.remove(key);
        }
        return;
    }
    if (keyword == "ifdef") {
        ++m_current_depth;
        if (m_state == State::Normal) {
            auto key = lexer.consume_until(' ');
            if (m_definitions.contains(key)) {
                m_depths_of_taken_branches.append(m_current_depth - 1);
                return;
            } else {
                m_depths_of_not_taken_branches.append(m_current_depth - 1);
                m_state = State::SkipIfBranch;
                return;
            }
        }
        return;
    }
    if (keyword == "ifndef") {
        ++m_current_depth;
        if (m_state == State::Normal) {
            auto key = lexer.consume_until(' ');
            if (!m_definitions.contains(key)) {
                m_depths_of_taken_branches.append(m_current_depth - 1);
                return;
            } else {
                m_depths_of_not_taken_branches.append(m_current_depth - 1);
                m_state = State::SkipIfBranch;
                return;
            }
        }
        return;
    }
    if (keyword == "if") {
        ++m_current_depth;
        if (m_state == State::Normal) {
            // FIXME: Implement #if logic
            // We currently always take #if branches.
            m_depths_of_taken_branches.append(m_current_depth - 1);
        }
        return;
    }

    if (keyword == "elif") {
        VERIFY(m_current_depth > 0);
        // FIXME: Evaluate the elif expression
        // We currently always treat the expression in #elif as true.
        if (m_depths_of_not_taken_branches.contains_slow(m_current_depth - 1) /* && should_take*/) {
            m_depths_of_not_taken_branches.remove_all_matching([this](auto x) { return x == m_current_depth - 1; });
            m_state = State::Normal;
        }
        if (m_depths_of_taken_branches.contains_slow(m_current_depth - 1)) {
            m_state = State::SkipElseBranch;
        }
        return;
    }
    if (keyword == "pragma") {
        lexer.consume_all();
        return;
    }

    if (!m_options.ignore_unsupported_keywords) {
        dbgln("Unsupported preprocessor keyword: {}", keyword);
        VERIFY_NOT_REACHED();
    }
}

const String& Preprocessor::processed_text()
{
    VERIFY(!m_processed_text.is_null());
    return m_processed_text;
}

};