#include <compiler.h>

global_variable constexpr u8 left_bracket = '[';
global_variable constexpr u8 right_bracket = ']';
global_variable constexpr u8 left_brace = '{';
global_variable constexpr u8 right_brace = '}';
global_variable constexpr u8 left_parenthesis = '(';
global_variable constexpr u8 right_parenthesis = ')';

fn bool is_space(u8 ch)
{
    return ((ch == ' ') | (ch == '\n')) | ((ch == '\t') | (ch == '\r'));
}

fn bool is_lower(u8 ch)
{
    return ((ch >= 'a') & (ch <= 'z'));
}

fn bool is_upper(u8 ch)
{
    return ((ch >= 'A') & (ch <= 'Z'));
}

fn bool is_decimal(u8 ch)
{
    return ((ch >= '0') & (ch <= '9'));
}

fn bool is_identifier_start(u8 ch)
{
    return (is_lower(ch) | is_upper(ch)) | (ch == '_');
}

fn bool is_identifier(u8 ch)
{
    return is_identifier_start(ch) | is_decimal(ch);
}

fn u32 get_line(Module& module)
{
    auto line = module.line_offset + 1;
    assert(line < ~(u32)0);
    return (u32)line;
}

fn u32 get_column(Module& module)
{
    auto column = module.offset - module.line_character_offset + 1;
    assert(column < ~(u32)0);
    return (u32)column;
}

fn bool consume_character_if_match(Module& module, u8 expected_ch)
{
    bool is_ch = false;
    auto i = module.offset;
    if (i < module.content.length)
    {
        auto ch = module.content[i];
        is_ch = expected_ch == ch;
        module.offset = i + 1;
    }

    return is_ch;
}

fn void expect_character(Module& module, u8 expected_ch)
{
    if (!consume_character_if_match(module, expected_ch))
    {
        report_error();
    }
}

fn void skip_space(Module& module)
{
    while (1)
    {
        auto iteration_offset = module.offset;

        while (module.offset < module.content.length)
        {
            auto ch = module.content[module.offset];
            if (!is_space(ch))
            {
                break;
            }

            module.line_offset += ch == '\n';
            module.line_character_offset = ch == '\n' ? module.offset : module.line_character_offset;
            module.offset += 1;
        }

        if (module.offset + 1 < module.content.length)
        {
            auto i = module.offset;
            auto first_ch = module.content[i];
            auto second_ch = module.content[i + 1];
            auto is_comment = first_ch == '/' && second_ch == '/';

            if (is_comment)
            {
                while (module.offset < module.content.length)
                {
                    auto ch = module.content[module.offset];
                    if (ch == '\n')
                    {
                        break;
                    }
                    module.offset += 1;
                }

                if (module.offset < module.content.length)
                {
                    module.line_offset += 1;
                    module.line_character_offset = module.offset;
                    module.offset += 1;
                }
            }
        }

        if (module.offset - iteration_offset == 0)
        {
            break;
        }
    }
}

fn String parse_identifier(Module& module)
{
    auto start = module.offset;

    if (is_identifier_start(module.content[start]))
    {
        module.offset = start + 1;

        while (module.offset < module.content.length)
        {
            auto i = module.offset;
            if (is_identifier(module.content[i]))
            {
                module.offset = i + 1;
            }
            else
            {
                break;
            }
        }
    }

    auto end = module.offset;
    if (end - start == 0)
    {
        report_error();
    }

    return module.content(start, end);
}

fn Type* parse_type(Module& module)
{
    trap_raw();
}

void parse(Module& module)
{
    while (1)
    {
        skip_space(module);

        if (module.offset == module.content.length)
        {
            break;
        }

        bool is_export = false;
        bool is_extern = false;

        auto global_line = get_line(module);
        auto global_column = get_column(module);

        if (consume_character_if_match(module, left_bracket))
        {
            while (module.offset < module.content.length)
            {
                auto global_keyword_string = parse_identifier(module);
                String global_keyword_strings[] = {
                    str("export"),
                    str("extern"),
                };
                enum class GlobalKeyword
                {
                    export_keyword,
                    extern_keyword,
                };

                u32 i;
                for (i = 0; i < array_length(global_keyword_strings); i += 1)
                {
                    String keyword = global_keyword_strings[i];
                    if (keyword.equal(global_keyword_string))
                    {
                        break;
                    }
                }

                if (i == array_length(global_keyword_strings))
                {
                    report_error();
                }

                auto global_keyword = (GlobalKeyword)i;
                switch (global_keyword)
                {
                    case GlobalKeyword::export_keyword:
                        {
                            is_export = true;
                        } break;
                    case GlobalKeyword::extern_keyword:
                        {
                            is_extern = true;
                        } break;
                }

                if (consume_character_if_match(module, right_bracket))
                {
                    break;
                }
                else
                {
                    report_error();
                }
            }

            skip_space(module);
        }

        auto global_name = parse_identifier(module);

        Global* last_global = module.first_global;
        while (last_global)
        {
            if (global_name.equal(last_global->variable.name))
            {
                report_error();
            }

            if (!last_global->next)
            {
                break;
            }

            last_global = last_global->next;
        }

        Type* type_it = module.first_type;
        Type* forward_declaration = 0;
        while (type_it)
        {
            if (global_name.equal(type_it->name))
            {
                if (type_it->id == TypeId::forward_declaration)
                {
                    forward_declaration = type_it;
                    break;
                }
                else
                {
                    report_error();
                }
            }

            if (!type_it->next)
            {
                break;
            }

            type_it = type_it->next;
        }

        Type* global_type = 0;

        if (consume_character_if_match(module, ':'))
        {
            skip_space(module);

            global_type = parse_type(module);

            skip_space(module);
        }

        trap_raw();
    }
}