//
// imag - the personal information management suite for the commandline
// Copyright (C) 2015, 2016 Matthias Beyer <mail@beyermatthias.de> and contributors
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; version
// 2.1 of the License.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//

use std::path::PathBuf;
use std::result::Result as RResult;
use std::ops::Deref;

use toml::{Parser, Value};

generate_error_module!(
    generate_error_types!(ConfigError, ConfigErrorKind,
        NoConfigFileFound   => "No config file found",

        ConfigOverrideError => "Config override error",
        ConfigOverrideKeyNotAvailable => "Key not available",
        ConfigOverrideTypeNotMatching => "Configuration Type not matching"

    );
);

use self::error::{ConfigError, ConfigErrorKind};

/**
 * Result type of this module. Either `T` or `ConfigError`
 */
pub type Result<T> = RResult<T, ConfigError>;

/// `Configuration` object
///
/// Holds all config variables which are globally available plus the configuration object from the
/// config parser, which can be accessed.
#[derive(Debug)]
pub struct Configuration {

    /// The plain configuration object for direct access if necessary
    config: Value,

    /// The verbosity the program should run with
    verbosity: bool,

    /// The editor which should be used
    editor: Option<String>,

    ///The options the editor should get when opening some file
    editor_opts: String,
}

impl Configuration {

    /// Get a new configuration object.
    ///
    /// The passed runtimepath is used for searching the configuration file, whereas several file
    /// names are tested. If that does not work, the home directory and the XDG basedir are tested
    /// with all variants.
    ///
    /// If that doesn't work either, an error is returned.
    pub fn new(rtp: &PathBuf) -> Result<Configuration> {
        fetch_config(&rtp).map(|cfg| {
            let verbosity   = get_verbosity(&cfg);
            let editor      = get_editor(&cfg);
            let editor_opts = get_editor_opts(&cfg);

            debug!("Building configuration");
            debug!("  - verbosity  : {:?}", verbosity);
            debug!("  - editor     : {:?}", editor);
            debug!("  - editor-opts: {}", editor_opts);

            Configuration {
                config: cfg,
                verbosity: verbosity,
                editor: editor,
                editor_opts: editor_opts,
            }
        })
    }

    pub fn editor(&self) -> Option<&String> {
        self.editor.as_ref()
    }

    #[allow(dead_code)] // Why do I actually need this annotation on a pub function?
    pub fn config(&self) -> &Value {
        &self.config
    }

    pub fn store_config(&self) -> Option<&Value> {
        match self.config {
            Value::Table(ref tabl) => tabl.get("store"),
            _ => None,
        }
    }

    /// Override the configuration.
    /// The `v` parameter is expected to contain 'key=value' pairs where the key is a path in the
    /// TOML tree, the value to be an appropriate value.
    ///
    /// The override fails if the configuration which is about to be overridden does not exist or
    /// the `value` part cannot be converted to the type of the configuration value.
    ///
    /// If `v` is empty, this is considered to be a successful `override_config()` call.
    pub fn override_config(&mut self, v: Vec<String>) -> Result<()> {
        use libimagutil::key_value_split::*;
        use libimagutil::iter::*;
        use self::error::ConfigErrorKind as CEK;
        use libimagerror::into::IntoError;

        v.into_iter()
            .map(|s| { debug!("Trying to process '{}'", s); s })
            .filter_map(|s| {
                match s.into_kv() {
                    Some(kv) => Some(kv.into()),
                    None => {
                        warn!("Could split at '=' - will be ignore override");
                        None
                    }
                }
            })
            .map(|(k, v)| {
                match self.config.lookup_mut(&k[..]) {
                    Some(value) => {
                        match into_value(value, v) {
                            Some(v) => {
                                *value = v;
                                info!("Successfully overridden: {} = {}", k, value);
                                Ok(())
                            },
                            None => Err(CEK::ConfigOverrideTypeNotMatching.into_error()),
                        }
                    },
                    None => Err(CEK::ConfigOverrideKeyNotAvailable.into_error()),
                }
            })
            .fold_defresult(|i| i)
            .map_err(Box::new)
            .map_err(|e| CEK::ConfigOverrideError.into_error_with_cause(e))
    }
}

/// Tries to convert the String `s` into the same type as `value`.
///
/// Returns None if string cannot be converted.
///
/// Arrays and Tables are not supported and will yield `None`.
fn into_value(value: &Value, s: String) -> Option<Value> {
    use std::str::FromStr;

    match value {
        &Value::String(_) => Some(Value::String(s)),
        &Value::Integer(_) => FromStr::from_str(&s[..]).ok().map(|i| Value::Integer(i)),
        &Value::Float(_) => FromStr::from_str(&s[..]).ok().map(|f| Value::Float(f)),
        &Value::Boolean(_) => {
            if s == "true" { Some(Value::Boolean(true)) }
            else if s == "false" { Some(Value::Boolean(false)) }
            else { None }
        }
        &Value::Datetime(_) => Some(Value::Datetime(s)),
        _ => None,
    }
}

impl Deref for Configuration {
    type Target = Value;

    fn deref(&self) -> &Value {
        &self.config
    }

}

fn get_verbosity(v: &Value) -> bool {
    match *v {
        Value::Table(ref t) => t.get("verbose")
                .map_or(false, |v| match *v { Value::Boolean(b) => b, _ => false, }),
        _ => false,
    }
}

fn get_editor(v: &Value) -> Option<String> {
    match *v {
        Value::Table(ref t) => t.get("editor")
                .and_then(|v| match *v { Value::String(ref s) => Some(s.clone()), _ => None, }),
        _ => None,
    }
}

fn get_editor_opts(v: &Value) -> String {
    match *v {
        Value::Table(ref t) => t.get("editor-opts")
                .and_then(|v| match *v { Value::String(ref s) => Some(s.clone()), _ => None, })
                .unwrap_or_default(),
        _ => String::new(),
    }
}

/**
 * Helper to fetch the config file
 *
 * Tests several variants for the config file path and uses the first one which works.
 */
fn fetch_config(rtp: &PathBuf) -> Result<Value> {
    use std::env;
    use std::fs::File;
    use std::io::Read;
    use std::io::Write;
    use std::io::stderr;

    use xdg_basedir;
    use itertools::Itertools;

    use libimagutil::variants::generate_variants as gen_vars;

    let variants = vec!["config", "config.toml", "imagrc", "imagrc.toml"];
    let modifier = |base: &PathBuf, v: &'static str| {
        let mut base = base.clone();
        base.push(String::from(v));
        base
    };

    vec![
        vec![rtp.clone()],
        gen_vars(rtp.clone(), variants.clone(), &modifier),

        env::var("HOME").map(|home| gen_vars(PathBuf::from(home), variants.clone(), &modifier))
                        .unwrap_or(vec![]),

        xdg_basedir::get_data_home().map(|data_dir| gen_vars(data_dir, variants.clone(), &modifier))
                                    .unwrap_or(vec![]),
    ].iter()
        .flatten()
        .filter(|path| path.exists() && path.is_file())
        .map(|path| {
            let content = {
                let mut s = String::new();
                let f = File::open(path);
                if f.is_err() {
                    return None
                }
                let mut f = f.unwrap();
                f.read_to_string(&mut s).ok();
                s
            };

            let mut parser = Parser::new(&content[..]);
            let res = parser.parse();

            if res.is_none() {
                write!(stderr(), "Config file parser error:").ok();
                for error in parser.errors {
                    write!(stderr(), "At [{}][{}] <> {}", error.lo, error.hi, error).ok();
                    write!(stderr(), "in: '{}'", &content[error.lo..error.hi]).ok();
                }
                None
            } else {
                res
            }
        })
        .filter(|loaded| loaded.is_some())
        .nth(0)
        .map(|inner| Value::Table(inner.unwrap()))
        .ok_or(ConfigErrorKind::NoConfigFileFound.into())
}