use serde::{Deserialize, Serialize};
use std::ffi::OsStr;
use std::io;
use std::path::{Path, PathBuf};

use super::local::LocalDriver;
use super::ssh::SshDriver;

/// Internal trait defining the strategy for executing a command.
///
/// This allows to have different execution behaviors (Local, SSH, ...) while keeping the
/// `ContextCommand` API consistent.
pub trait CommandRunner {
    fn add_arg(&mut self, arg: String);
    fn status(&mut self) -> io::Result<std::process::ExitStatus>;
    fn output(&mut self) -> io::Result<std::process::Output>;
}

pub trait ContextDriver {
    fn ensure_available(&self, src: &Path, dest_root: &str) -> io::Result<PathBuf>;
    fn retrieve_path(&self, src: &Path, dest: &Path) -> io::Result<()>;
    fn list_files(&self, path: &Path) -> io::Result<Vec<PathBuf>>;
    fn create_runner(&self, program: String) -> Box<dyn CommandRunner>;
    fn prepare_work_dir(&self) -> io::Result<String>;
}

/// Represents an execution environment (Local or via SSH).
///
/// This is the data model that configuration files store. It defines *where* operations happen.
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
#[serde(tag = "type")]
#[derive(Default)]
pub enum Context {
    #[serde(rename = "local")]
    #[default]
    Local,
    #[serde(rename = "ssh")]
    Ssh {
        host: String,
        user: Option<String>,
        port: Option<u16>,
    },
}

impl Context {
    pub fn command<S: AsRef<OsStr>>(&self, program: S) -> ContextCommand {
        let runner = self
            .driver()
            .create_runner(program.as_ref().to_string_lossy().to_string());
        ContextCommand { runner }
    }

    /// Ensures that the source file/directory exists at the destination context.
    ///
    /// If Local: Returns the absolute path of `src`.
    /// If Remote: Copies `src` to `dest_root` on the remote and returns the path to the copied entity.
    pub fn ensure_available(&self, src: &Path, dest_root: &str) -> io::Result<PathBuf> {
        self.driver().ensure_available(src, dest_root)
    }

    pub fn prepare_work_dir(&self) -> io::Result<String> {
        self.driver().prepare_work_dir()
    }

    /// Retrieve a file or directory from the context to the local filesystem.
    ///
    /// The `src` path is on the context, `dest` is on the local machine.
    /// If `src` is a directory, it is copied recursively.
    pub fn retrieve_path(&self, src: &Path, dest: &Path) -> io::Result<()> {
        self.driver().retrieve_path(src, dest)
    }

    /// List files in a directory on the context.
    pub fn list_files(&self, path: &Path) -> io::Result<Vec<PathBuf>> {
        self.driver().list_files(path)
    }

    fn driver(&self) -> Box<dyn ContextDriver> {
        match self {
            Context::Local => Box::new(LocalDriver),
            Context::Ssh { host, user, port } => Box::new(SshDriver {
                host: host.clone(),
                user: user.clone(),
                port: *port,
            }),
        }
    }
}

/// A builder and executor for commands within a specific `Context`.
///
/// This struct acts as a high-level facade (API) for command creation. It hides the implementation
/// details of *how* the command is actually executed, allowing the user to simple chain arguments
/// and call `status()` or `output()`.
///
/// It delegates the actual work to a `CommandRunner`.
pub struct ContextCommand {
    runner: Box<dyn CommandRunner>,
}

impl ContextCommand {
    pub fn arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut Self {
        self.runner
            .add_arg(arg.as_ref().to_string_lossy().to_string());
        self
    }

    // Support chaining args
    pub fn args<I, S>(&mut self, args: I) -> &mut Self
    where
        I: IntoIterator<Item = S>,
        S: AsRef<OsStr>,
    {
        for arg in args {
            self.arg(arg);
        }
        self
    }

    pub fn status(&mut self) -> io::Result<std::process::ExitStatus> {
        self.runner.status()
    }

    // Capture output
    pub fn output(&mut self) -> io::Result<std::process::Output> {
        self.runner.output()
    }
}