module readconf;

import std.stdio, std.conv, std.path, std.file;
import core.stdc.stdlib : exit;
import std.regex;
import std.meta;
import singlog;

/** 
 * **Get an object to read the configuration file**
 * 
 * - The `read()` will allow you to read the configuration file
 * - `cf()` or `configFile()` will allow you to refer to the read file to get the parameters
 */
alias rc = Config.file;

private const string mainSection = "[]";

class Config
{
private:
    enum {
        GROUP_PARAMETER           = 4,
        GROUP_VALUE_1             = 12, // string
        GROUP_VALUE_2             = 15, // "strin"
        GROUP_VALUE_3             = 17, // 'string'
        GROUP_SECTION_OTHER_OUTER = 19, // [string]
        GROUP_SECTION_OTHER_INNER = 20, // string
        GROUP_SECTION_MAIN        = 23, // []
    }

    static Config config;
    string path;
    bool readed = false;
    ConfigFile[string] configs;

    const string pattern = "^( |\\t)*((((\\w(\\w|-)?)+)(( |\\t)*(=>|=){1}"
        ~ "( |\\t)*)(?!\\/(\\/|\\*))(([^ >\"'=\\n\\t#;].*?)|(\"(.+)?\")"
        ~ "|('(.+)?')|()){1})|(\\[((\\w(\\w|-)?)+)\\])|(\\[\\]))( |\\t)*"
        ~ "(( |\\t)(#|;|\\/\\/|\\/\\*).*)?$";

    /** 
     * Reading the configuration file
     */
    bool readConfig(const string configName)
    {
        File configuration;

        try {
            configuration = File(this.path, "r");
        } catch (Exception e) {
            log.w("Unable to open the configuration file " ~ this.path);
            log.e(e);
            return false;
        }

        if (configName !in this.configs)
            this.configs[configName] = ConfigFile(configName);

        auto regular = regex(this.pattern, "m");

        // reading from the main section
        string sectionName = mainSection;

        while (!configuration.eof())
        {
            string line = configuration.readln();
            auto match = matchFirst(line, regular);

            if (match.length == 0)
                continue;
            
            // if again main section
            if (match[GROUP_SECTION_MAIN].length)
            {
                sectionName = match[GROUP_SECTION_MAIN];
                continue;
            }
            if (match[GROUP_SECTION_OTHER_OUTER].length)
            {
                sectionName = match[GROUP_SECTION_OTHER_INNER];
                continue;
            }

            int group = GROUP_VALUE_1;

            if (match[group].length) {
                if (match[group][0] == '\"')
                    group = GROUP_VALUE_2;
                else if (match[group][0] == '\'')
                    group = GROUP_VALUE_3;
            }

            this.configs[configName].add(sectionName, ConfigParameter(match[GROUP_PARAMETER], match[group]));
        }

        try {
            configuration.close();
            this.readed = true;
        } catch (Exception e) {
            log.w("Unable to close the configuration file " ~ this.path);
            log.e(e);
            this.configs.remove(configName);
            this.readed = false;
        }

        return this.readed;
    }

    this() {}

public:
    /** 
     * Accessing the Config object
     * Returns: Config Object
     */
    @property static Config file()
    {
        if (this.config is null)
            this.config = new Config;

        return this.config;
    }

    /** 
     * Read the configuration file
     * Params:
     *   path = the path to the configuration file
     *   configName = a specific name to bind to the configuration file (default file name)
     * Returns: `true` if the file was read successfully
     */
    bool read(string path, string configName = "")
    {
        this.path = path;
        if (!path.exists)
            throw new Exception("The configuration file does not exist: " ~ path);
        if (configName.length == 0)
            configName = path.baseName();
        if (configName in configs)
            throw new Exception("The configuration file with this name has already been read");
        return readConfig(configName);
    }

    /** 
     * Accessing the read configuration file
     * Params:
     *   configName = specific name to bind to the configuration file
     *   (if the read files are > 1, then specify a specific name, otherwise default file name)
     * Returns: configuration file object ConfigFile
     */
    @property ConfigFile configFile(string configName = "")
    {
        if (configName.length == 0)
        {
            if (configs.length == 1)
                return configs[configs.byKey.front];
            else
                throw new Exception("You must explicitly specify the name of the configuration file");
        }

        return configName in configs ? configs[configName] : ConfigFile(configName);
    }

    /** 
     * Get the read configuration file
     * Params:
     *   configName = specific name to bind to the configuration file
     *   (if the read files are > 1, then specify a specific name, otherwise default file name)
     * Returns: configuration file object ConfigFile
     */
    alias cf = configFile;

    @property ConfigFile opIndex(string configName = "")
    {
        if (configName.length == 0)
        {
            if (configs.length == 1)
                return configs[configs.byKey.front];
            else
                throw new Exception("More than one configuration file has been read. "
                    ~ "It is necessary to specify the name of a specific");
        }

        return configName in configs ? configs[configName] : ConfigFile(configName);
    }
}

struct ConfigFile
{
    private string name;
    private ConfigSection[string] sections;

    @property bool exist()
    {
        return this.sections.length > 0;
    }

    /** 
     * Get the section
     * Params:
     *   section = section name (default main section)
     * Returns: the object of the configuration file section ConfigSection
     */
    @property ConfigSection sectionName(string section = mainSection)
    {
        if (!this.exist)
            throw new Exception("The configuration file does not exist");
        if (section == mainSection && sections.length == 1)
            return sections[sections.byKey.front];
        if (section.length == 0)
            section = mainSection;
        if (section !in sections)
            throw new Exception("The selected section does not exist");

        return sections[section];
    }

     /** 
     * Get the section
     * Params:
     *   section = section name (default main section)
     * Returns: the object of the configuration file section ConfigSection
     */
    alias sn = sectionName;

    private void add(string sectionName, ConfigParameter parameter)
    {
        if (sectionName !in this.sections)
            this.sections[sectionName] = ConfigSection(sectionName);

        this.sections[sectionName].add(parameter);
    }

    @property ConfigSection opIndex(string section = mainSection)
    {
        if (!this.exist)
            throw new Exception("The configuration file does not exist");
        if (section == mainSection && sections.length == 1)
            return sections[sections.byKey.front];
        if (section.length == 0)
            section = mainSection;
        if (section !in sections)
            throw new Exception("The selected section does not exist");

        return sections[section];
    }
}

struct ConfigSection
{
    private string name = mainSection;
    private ConfigParameter[string] parameters;

    /** 
     * Checking for the presence of a partition
     * Returns: true if the parameter is missing, otherwise false
     */
    @property bool empty()
    {
        return this.parameters.length == 0;
    }

    /** 
     * Get the parameter value
     * Params:
     *   key = parameter from the configuration file
     * Returns: the object of the parameter ConfigParameter
     */
    ConfigParameter key(string key)
    {
        if (key.length == 0)
            throw new Exception("The key cannot be empty");
        if (this.empty)
            throw new Exception("The selected section has no parameters or does not exist");
        return key in this.parameters ? this.parameters[key] : ConfigParameter(key);
    }

    /** 
     * Get all keys and their values
     * Returns: collection of parameters
     */
    ConfigParameter[string] keys()
    {
        return this.parameters;
    }

    private void add(ConfigParameter parameter)
    {
        if (parameter.property in parameters)
            log.w("The parameter exists but will be overwritten");
        this.parameters[parameter.property] = parameter;
    }

    ConfigParameter opIndex(string key)
    {
        if (key.length == 0)
            throw new Exception("The key cannot be empty");
        if (this.empty)
            throw new Exception("The selected section has no parameters or does not exist");
        return key in this.parameters ? this.parameters[key] : ConfigParameter(key);
    }
}

struct ConfigParameter
{
    private string property;
    private string value;

    /** 
     * Checking for the presence of a parameter
     * Returns: true if the parameter is missing, otherwise false
     */
    @property bool empty()
    {
        return this.value.length == 0;
    }

    /** 
     * Get a string representation of the value
     * Returns: default string value
     */
    @property string toString() const
    {
        return this.value;
    }

    alias toString this;

    auto opCast(T)() const
    {
        try {
            return this.value.to!T;
        } catch (Exception e) {
            log.w("Cannot convert type");
            log.e(e);
            return T.init;
        }
    }
}