//
// imag - the personal information management suite for the commandline
// Copyright (C) 2015-2018 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::process::Command;
use std::env;
use std::process::exit;
use std::io::Stdin;
use std::sync::Arc;

pub use clap::App;
use clap::AppSettings;
use toml::Value;
use toml_query::read::TomlValueReadExt;

use clap::{Arg, ArgMatches};
use failure::ResultExt;
use failure::Fallible as Result;
use failure::Error;
use failure::err_msg;

use configuration::{fetch_config, override_config, InternalConfiguration};
use logger::ImagLogger;
use io::OutputProxy;

use libimagerror::errors::ErrorMsg as EM;
use libimagerror::trace::*;
use libimagstore::store::Store;
use libimagstore::file_abstraction::InMemoryFileAbstraction;
use libimagutil::debug_result::DebugResult;
use spec::CliSpec;

/// The Runtime object
///
/// This object contains the complete runtime environment of the imag application running.
#[derive(Debug)]
pub struct Runtime<'a> {
    rtp: PathBuf,
    configuration: Option<Value>,
    cli_matches: ArgMatches<'a>,
    store: Store,
}

impl<'a> Runtime<'a> {

    /// Gets the CLI spec for the program and retreives the config file path (or uses the default on
    /// in $HOME/.imag/config, $XDG_CONFIG_DIR/imag/config or from env("$IMAG_CONFIG")
    /// and builds the Runtime object with it.
    ///
    /// The cli_app object should be initially build with the ::get_default_cli_builder() function.
    pub fn new<C>(cli_app: C) -> Result<Runtime<'a>>
        where C: Clone + CliSpec<'a> + InternalConfiguration
    {
        use libimagerror::trace::trace_error;

        let matches = cli_app.clone().matches();

        let rtp = get_rtp_match(&matches);

        let configpath = matches.value_of(Runtime::arg_config_name())
                                .map_or_else(|| rtp.clone(), PathBuf::from);

        debug!("Config path = {:?}", configpath);

        let config = match fetch_config(&configpath)? {
            None => {
                return Err(err_msg("No configuration file found"))
                    .context(err_msg("Maybe try to use 'imag-init' to initialize imag?"))
                    .context(err_msg("Continuing without configuration file"))
                    .context(err_msg("Cannot instantiate runtime"))
                    .map_err(Error::from);
            },
            Some(mut config) => {
                if let Err(e) = override_config(&mut config, get_override_specs(&matches)) {
                    error!("Could not apply config overrides");
                    trace_error(&e);

                    // TODO: continue question (interactive)
                }

                Some(config)
            }
        };

        Runtime::_new(cli_app, matches, config)
    }

    /// Builds the Runtime object using the given `config`.
    pub fn with_configuration<C>(cli_app: C, config: Option<Value>) -> Result<Runtime<'a>>
        where C: Clone + CliSpec<'a> + InternalConfiguration
    {
        let matches = cli_app.clone().matches();
        Runtime::_new(cli_app, matches, config)
    }

    fn _new<C>(cli_app: C, matches: ArgMatches<'a>, config: Option<Value>) -> Result<Runtime<'a>>
    where C: Clone + CliSpec<'a> + InternalConfiguration
    {
        if cli_app.enable_logging() {
            Runtime::init_logger(&matches, config.as_ref())
        }

        let rtp = get_rtp_match(&matches);

        let storepath = matches.value_of(Runtime::arg_storepath_name())
                                .map_or_else(|| {
                                    let mut spath = rtp.clone();
                                    spath.push("store");
                                    spath
                                }, PathBuf::from);

        debug!("RTP path    = {:?}", rtp);
        debug!("Store path  = {:?}", storepath);

        let store_result = if cli_app.use_inmemory_fs() {
            Store::new_with_backend(storepath,
                                    &config,
                                    Arc::new(InMemoryFileAbstraction::default()))
        } else {
            Store::new(storepath, &config)
        };

        store_result.map(|store| {
            Runtime {
                cli_matches: matches,
                configuration: config,
                rtp: rtp,
                store: store,
            }
        })
        .context(err_msg("Cannot instantiate runtime"))
        .map_err(Error::from)
    }

    ///
    /// Get a commandline-interface builder object from `clap`
    ///
    /// This commandline interface builder object already contains some predefined interface flags:
    ///   * -v | --verbose for verbosity
    ///   * --debug for debugging
    ///   * -c <file> | --config <file> for alternative configuration file
    ///   * -r <path> | --rtp <path> for alternative runtimepath
    ///   * --store <path> for alternative store path
    /// Each has the appropriate help text included.
    ///
    /// The `appname` shall be "imag-<command>".
    ///
    pub fn get_default_cli_builder(appname: &'a str,
                                   version: &'a str,
                                   about: &'a str)
        -> App<'a, 'a>
    {
        App::new(appname)
            .version(version)
            .author("Matthias Beyer <mail@beyermatthias.de>")
            .about(about)
            .settings(&[AppSettings::AllowExternalSubcommands])
            .arg(Arg::with_name(Runtime::arg_verbosity_name())
                .short("v")
                .long("verbose")
                .help("Set log level")
                .required(false)
                .takes_value(true)
                .possible_values(&["trace", "debug", "info", "warn", "error"])
                .default_value("info")
                .value_name("LOGLEVEL"))

            .arg(Arg::with_name(Runtime::arg_debugging_name())
                .long("debug")
                .help("Enables debugging output. Shortcut for '--verbose debug'")
                .required(false)
                .takes_value(false))

            .arg(Arg::with_name(Runtime::arg_no_color_output_name())
                .long("no-color")
                .help("Disable color output")
                .required(false)
                .takes_value(false))

            .arg(Arg::with_name(Runtime::arg_config_name())
                .long("config")
                .help("Path to alternative config file")
                .required(false)
                .validator(::libimagutil::cli_validators::is_existing_path)
                .takes_value(true))

            .arg(Arg::with_name(Runtime::arg_config_override_name())
                 .long("override-config")
                 .help("Override a configuration settings. Use 'key=value' pairs, where the key is a path in the TOML configuration. The value must be present in the configuration and be convertible to the type of the configuration setting. If the argument does not contain a '=', it gets ignored. Setting Arrays and Tables is not yet supported.")
                 .required(false)
                 .takes_value(true))

            .arg(Arg::with_name(Runtime::arg_runtimepath_name())
                .long("rtp")
                .help("Alternative runtimepath")
                .required(false)
                .validator(::libimagutil::cli_validators::is_directory)
                .takes_value(true))

            .arg(Arg::with_name(Runtime::arg_storepath_name())
                .long("store")
                .help("Alternative storepath. Must be specified as full path, can be outside of the RTP")
                .required(false)
                .validator(::libimagutil::cli_validators::is_directory)
                .takes_value(true))

            .arg(Arg::with_name(Runtime::arg_editor_name())
                .long("editor")
                .help("Set editor")
                .required(false)
                .takes_value(true))

            .arg(Arg::with_name(Runtime::arg_logdest_name())
                .long(Runtime::arg_logdest_name())
                .help("Override the logging destinations from the configuration: values can be seperated by ',', a value of '-' marks the stderr output, everything else is expected to be a path")
                .required(false)
                .takes_value(true)
                .value_name("LOGDESTS"))

    }

    /// Get the argument names of the Runtime which are available
    pub fn arg_names() -> Vec<&'static str> {
        vec![
            Runtime::arg_verbosity_name(),
            Runtime::arg_debugging_name(),
            Runtime::arg_no_color_output_name(),
            Runtime::arg_config_name(),
            Runtime::arg_config_override_name(),
            Runtime::arg_runtimepath_name(),
            Runtime::arg_storepath_name(),
            Runtime::arg_editor_name(),
        ]
    }

    /// Get the verbosity argument name for the Runtime
    pub fn arg_verbosity_name() -> &'static str {
        "verbosity"
    }

    /// Get the debugging argument name for the Runtime
    pub fn arg_debugging_name() -> &'static str {
        "debugging"
    }

    /// Get the argument name for no color output of the Runtime
    pub fn arg_no_color_output_name() -> &'static str {
        "no-color-output"
    }

    /// Get the config argument name for the Runtime
    pub fn arg_config_name() -> &'static str {
        "config"
    }

    /// Get the config-override argument name for the Runtime
    pub fn arg_config_override_name() -> &'static str {
        "config-override"
    }

    /// Get the runtime argument name for the Runtime
    pub fn arg_runtimepath_name() -> &'static str {
        "runtimepath"
    }

    /// Get the storepath argument name for the Runtime
    pub fn arg_storepath_name() -> &'static str {
        "storepath"
    }

    /// Get the editor argument name for the Runtime
    pub fn arg_editor_name() -> &'static str {
        "editor"
    }

    /// Extract the Store object from the Runtime object, destroying the Runtime object
    ///
    /// # Warning
    ///
    /// This function is for testing _only_! It can be used to re-build a Runtime object with an
    /// alternative Store.
    #[cfg(feature = "testing")]
    pub fn extract_store(self) -> Store {
        self.store
    }

    /// Re-set the Store object within
    ///
    /// # Warning
    ///
    /// This function is for testing _only_! It can be used to re-build a Runtime object with an
    /// alternative Store.
    #[cfg(feature = "testing")]
    pub fn with_store(mut self, s: Store) -> Self {
        self.store = s;
        self
    }

    /// Get the argument name for the logging destination
    pub fn arg_logdest_name() -> &'static str {
        "logging-destinations"
    }

    /// Initialize the internal logger
    ///
    /// If the environment variable "IMAG_LOG_ENV" is set, this simply
    /// initializes a env-logger instance. Errors are ignored in this case.
    /// If the environment variable is not set, this initializes the internal imag logger. On
    /// error, this exits (as there is nothing we can do about that)
    ///
    fn init_logger(matches: &ArgMatches, config: Option<&Value>) {
        use log::set_max_level;
        use log::set_boxed_logger;
        use std::env::var as env_var;
        use env_logger;

        if env_var("IMAG_LOG_ENV").is_ok() {
            let _ = env_logger::try_init();
        } else {
            let logger = ImagLogger::new(matches, config)
                .map_err_trace()
                .unwrap_or_else(|_| exit(1));

            set_max_level(logger.global_loglevel().to_level_filter());

            debug!("Init logger with {}", logger.global_loglevel());

            set_boxed_logger(Box::new(logger))
                .map_err(|e| panic!("Could not setup logger: {:?}", e))
                .ok();
        }
    }

    /// Get the verbosity flag value
    pub fn is_verbose(&self) -> bool {
        self.cli_matches.is_present("verbosity")
    }

    /// Get the debugging flag value
    pub fn is_debugging(&self) -> bool {
        self.cli_matches.is_present("debugging")
    }

    /// Get the runtimepath
    pub fn rtp(&self) -> &PathBuf {
        &self.rtp
    }

    /// Get the commandline interface matches
    pub fn cli(&self) -> &ArgMatches {
        &self.cli_matches
    }

    /// Get the configuration object
    pub fn config(&self) -> Option<&Value> {
        self.configuration.as_ref()
    }

    /// Get the store object
    pub fn store(&self) -> &Store {
        &self.store
    }

    /// Get a editor command object which can be called to open the $EDITOR
    pub fn editor(&self) -> Result<Option<Command>> {
        self.cli()
            .value_of("editor")
            .map(String::from)
            .or_else(|| {
                self.config()
                    .and_then(|v| match v.read("rt.editor") {
                        Ok(Some(&Value::String(ref s))) => Some(s.clone()),
                        _ => None, // FIXME silently ignore errors in config is bad
                    })
            })
            .or(env::var("EDITOR").ok())
            .ok_or_else(|| Error::from(EM::IO))
            .map_dbg(|s| format!("Editing with '{}'", s))
            .and_then(|s| {
                let mut split = s.split_whitespace();
                let command   = split.next();
                if command.is_none() {
                    return Ok(None)
                }
                let mut c = Command::new(command.unwrap()); // secured above
                c.args(split);
                c.stdin(::std::fs::File::open("/dev/tty").context(EM::IO)?);
                c.stderr(::std::process::Stdio::inherit());
                Ok(Some(c))
            })
    }

    pub fn stdout(&self) -> OutputProxy {
        OutputProxy::Out(::std::io::stdout())
    }

    pub fn stderr(&self) -> OutputProxy {
        OutputProxy::Err(::std::io::stderr())
    }

    pub fn stdin(&self) -> Option<Stdin> {
        Some(::std::io::stdin())
    }

    /// Helper for handling subcommands which are not available.
    ///
    /// # Example
    ///
    /// For example someone calls `imag foo bar`. If `imag-foo` is in the $PATH, but it has no
    /// subcommand `bar`, the `imag-foo` binary is able to automatically forward the invokation to a
    /// `imag-foo-bar` binary which might be in $PATH.
    ///
    /// It needs to call `Runtime::handle_unknown_subcommand` with the following parameters:
    ///
    /// 1. The "command" which was issued. In the example this would be `"imag-foo"`
    /// 2. The "subcommand" which is missing: `"bar"` in the example
    /// 3. The `ArgMatches` object from the call, so that this routine can forward all flags passed
    ///    to the `bar` subcommand.
    ///
    /// # Warning
    ///
    /// If, and only if, the subcommand does not exist (as in `::std::io::ErrorKind::NotFound`),
    /// this function exits with 1 as exit status.
    ///
    /// # Return value
    ///
    /// On success, the exit status object of the `Command` invocation is returned.
    ///
    /// # Details
    ///
    /// The `IMAG_RTP` variable is set for the child process. It is set to the current runtime path.
    ///
    /// Stdin, stdout and stderr are inherited to the child process.
    ///
    /// This function **blocks** until the child returns.
    ///
    pub fn handle_unknown_subcommand<S: AsRef<str>>(&self,
                                                    command: S,
                                                    subcommand: S,
                                                    args: &ArgMatches)
        -> Result<::std::process::ExitStatus>
    {
        use std::io::Write;
        use std::io::ErrorKind;

        let rtp_str = self.rtp()
            .to_str()
            .map(String::from)
            .ok_or_else(|| Error::from(EM::IO))?;

        let command = format!("{}-{}", command.as_ref(), subcommand.as_ref());

        let subcommand_args = args.values_of("")
            .map(|sx| sx.map(String::from).collect())
            .unwrap_or_else(|| vec![]);

        Command::new(&command)
            .stdin(::std::process::Stdio::inherit())
            .stdout(::std::process::Stdio::inherit())
            .stderr(::std::process::Stdio::inherit())
            .args(&subcommand_args[..])
            .env("IMAG_RTP", rtp_str)
            .spawn()
            .and_then(|mut c| c.wait())
            .map_err(|e| match e.kind() {
                ErrorKind::NotFound => {
                    let mut out = self.stdout();

                    if let Err(e) = writeln!(out, "No such command: '{}'", command) {
                        return e;
                    }
                    if let Err(e) = writeln!(out, "See 'imag --help' for available subcommands") {
                        return e;
                    }

                    ::std::process::exit(1)
                },
                _ => e,
            })
            .context(EM::IO)
            .map_err(Error::from)
    }
}

/// Exported for the `imag` command, you probably do not want to use that.
pub fn get_rtp_match<'a>(matches: &ArgMatches<'a>) -> PathBuf {
    use std::env;

    matches.value_of(Runtime::arg_runtimepath_name())
        .map_or_else(|| {
            if let Ok(home) = env::var("IMAG_RTP") {
                return PathBuf::from(home);
            }

            match env::var("HOME") {
                Ok(home) => {
                    let mut p = PathBuf::from(home);
                    p.push(".imag");
                    return p;
                },
                Err(_) => panic!("You seem to be $HOME-less. Please get a $HOME before using this \
                    software. We are sorry for you and hope you have some \
                    accommodation anyways."),
            }
        }, PathBuf::from)
}

fn get_override_specs(matches: &ArgMatches) -> Vec<String> {
    matches
        .values_of("config-override")
        .map(|values| {
             values
             .filter(|s| {
                 let b = s.contains("=");
                 if !b { warn!("override '{}' does not contain '=' - will be ignored!", s); }
                 b
             })
             .map(String::from)
             .collect()
        })
        .unwrap_or(vec![])
}