// ────────────────────────────────────────────────────────────────
// Imports
// ────────────────────────────────────────────────────────────────
use std::fs;
use std::io::{ErrorKind, Read};
use std::path::{Path, PathBuf};

use serde::Serialize;
use serde::de::DeserializeOwned;

use crate::filesystem::{FsError, LegacyFileSystem};

// ────────────────────────────────────────────────────────────────
// Concrete implementation
// ────────────────────────────────────────────────────────────────
/// The concrete file‑system.  All paths are interpreted relative to
/// `project_root`.
pub struct NativeFileSystem {
    project_root: PathBuf,
}

impl NativeFileSystem {
    /// Create a new instance.
    pub fn new(root: impl Into<PathBuf>) -> Self {
        Self {
            project_root: root.into(),
        }
    }

    /// Resolve the user supplied *relative* path against the project root.
    #[inline]
    fn full_path(&self, path: &Path) -> PathBuf {
        self.project_root.join(path)
    }
}

// ────────────────────────────────────────────────────────────────
// Implementation of the trait
// ────────────────────────────────────────────────────────────────
impl LegacyFileSystem for NativeFileSystem {
    fn read<T: DeserializeOwned>(&self, path: &Path) -> Result<T, FsError> {
        let full_path = self.full_path(path);
        let file = fs::File::open(full_path).map_err(FsError::Io)?;
        serde_json::from_reader(file).map_err(FsError::Serde)
    }

    fn read_bytes(&self, path: &Path) -> Result<Vec<u8>, FsError> {
        let full_path = self.full_path(path);
        let mut contents = Vec::new();
        fs::File::open(full_path)?.read_to_end(&mut contents)?;
        Ok(contents)
    }

    fn write<T: Serialize>(&self, path: &Path, data: T) -> Result<(), FsError> {
        let full_path = self.full_path(path);

        // Ensure the parent directory exists.
        if let Some(parent) = full_path.parent() {
            fs::create_dir_all(parent)?;
        }

        let file = fs::File::create(full_path)?;
        serde_json::to_writer(file, &data).map_err(FsError::Serde)
    }

    fn delete(&self, path: &Path) -> Result<(), FsError> {
        let full_path = self.full_path(path);
        match fs::remove_file(&full_path) {
            Ok(()) => Ok(()),
            Err(e) if e.kind() == ErrorKind::IsADirectory => {
                // Remove a directory tree.
                fs::remove_dir_all(full_path).map_err(FsError::Io)
            }
            Err(e) => Err(FsError::Io(e)),
        }
    }

    fn mkdir(&self, path: &Path) -> Result<(), FsError> {
        let full_path = self.full_path(path);
        fs::create_dir_all(full_path).map_err(FsError::Io)
    }

    fn exists(&self, path: &Path) -> bool {
        let full_path = self.full_path(path);
        full_path.exists()
    }

    fn rename(&self, path: &Path, other: &Path) -> Result<(), FsError> {
        let full_path = self.full_path(path);
        let full_other = self.full_path(other);
        fs::rename(full_path, full_other).map_err(FsError::Io)
    }

    fn config_path(&self) -> PathBuf {
        match std::env::var("HOME") {
            Ok(path) => PathBuf::from(path + "/.config/worldcoder/settings.json"),
            Err(_) => {
                eprintln!(
                    "XDG_CONFIG_HOME not set, using default path of ~/.config/worldcoder/settings.json"
                );
                "~/.config/worldcoder/settings.json".into()
            }
        }
    }
}