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extern crate config;
use self::config::types::{Config, ScalarValue, Value};

use std::env::home_dir;
use std::process::Command;

/// A command with arguments.
pub struct CommandLine {
    program: String,
    args: Vec<String>,
}

fn expand_home(path: &String) -> String {
    if path.starts_with("~/") {
        if let Some(home) = home_dir() {
            return format!("{}/{}", home.display(), &path[2..])
        }
    }

    path.clone()
}

fn make_command_vec(vec: &Vec<Value>) -> Result<CommandLine, String> {
    if vec.is_empty() {
        return Err(format!("empty execution vector"));
    }

    let mut prog_args = vec![];
    for v in vec {
        match *v {
            Value::Svalue(ref sv) =>
                match *sv {
                    ScalarValue::Str(ref s) => prog_args.push(s),
                    _ => return Err(format!("non-string program value")),
                },
            _ => return Err(format!("non-string program value")),
        }
    }

    let (prog, args) = prog_args.split_at(1);
    Ok(CommandLine {
        program: expand_home(prog[0]),
        // XXX: Why does .cloned() not work?
        args: args.iter().map(|&arg| (*arg).clone()).collect(),
    })
}

fn make_command_str(string: &String) -> Result<CommandLine, String> {
    if string.is_empty() {
        Err(format!("empty execution string"))
    } else {
        Ok(CommandLine {
            program: expand_home(string),
            args: vec![],
        })
    }
}

/// Reads a command line from the configuration with the given configuration key.
///
/// If the configuration is a string, it is interpreted as a program with no arguments. A list of
/// strings is taken to be a program with arguments. The program supports expanding the `~/` token
/// to be the home directory of the current user.
///
/// All other configuration types are ignored.
pub fn read_command_line_from_config(conf: &Config, path: &str) -> Option<CommandLine> {
    conf.lookup(path).and_then(|val| {
        let cmd_line = match *val {
            Value::Array(ref a) => make_command_vec(a),
            Value::Svalue(ref sv) =>
                match *sv {
                    ScalarValue::Str(ref s) => make_command_str(s),
                    _ => Err(format!("unsupported type for {}", path)),
                },
            _ => Err(format!("unsupported type for {}", path)),
        };

        cmd_line.map_err(|err| {
            println!("Failed to make a command line for '{}': {:?}", path, err);
        }).ok()
    })
}

/// Runs a command line.
pub fn run_command_line(cmd_line: &CommandLine) -> Result<(), String> {
    let cmd = Command::new(&cmd_line.program)
                .args(&cmd_line.args)
                .output();

    match cmd {
        Ok(output) =>
            if output.status.success() {
                Ok(())
            } else {
                Err(format!("failed to execute process ({:?}):\noutput:\n{}\nerror:{}",
                            output.status.code(),
                            String::from_utf8_lossy(&output.stdout),
                            String::from_utf8_lossy(&output.stderr)))
            },
        _ => Err(format!("failed to execute process")),
    }
}