use super::{VfsError, VfsStat};
use chrono::Datelike;
use std::os::unix::fs::PermissionsExt;
use std::path::Path;

/// 从 std::io::ErrorKind 映射 VfsError
pub fn map_io_error(path: &Path, e: std::io::Error) -> VfsError {
    match e.kind() {
        std::io::ErrorKind::NotFound => VfsError::NotFound(path.display().to_string()),
        std::io::ErrorKind::PermissionDenied => {
            VfsError::PermissionDenied(path.display().to_string())
        }
        std::io::ErrorKind::AlreadyExists => VfsError::AlreadyExists(path.display().to_string()),
        std::io::ErrorKind::DirectoryNotEmpty => VfsError::NotEmpty(path.display().to_string()),
        std::io::ErrorKind::NotADirectory => VfsError::NotADirectory(path.display().to_string()),
        std::io::ErrorKind::IsADirectory => VfsError::IsADirectory(path.display().to_string()),
        std::io::ErrorKind::UnexpectedEof => VfsError::UnexpectedEof,
        other => VfsError::Io(format!("{}: {}", other, path.display())),
    }
}

/// 从 std::fs::Metadata 构建 VfsStat
pub fn stat_from_metadata(meta: &std::fs::Metadata, is_symlink: bool) -> VfsStat {
    #[cfg(unix)]
    use std::os::unix::fs::MetadataExt;

    let mut stat = VfsStat::new();
    stat.size = meta.len();
    stat.is_dir = meta.is_dir();
    stat.is_symlink = is_symlink;

    #[cfg(unix)]
    {
        stat.mode = meta.permissions().mode();
        stat.uid = meta.uid();
        stat.gid = meta.gid();
    }

    #[cfg(not(unix))]
    {
        stat.mode = if meta.is_dir() { 0o40755 } else { 0o100644 };
    }

    if let Ok(t) = meta.accessed() {
        stat.atime = t;
    }
    if let Ok(t) = meta.modified() {
        stat.mtime = t;
    }

    stat
}

/// 构建目录条目的 long_name（类似 ls -l 格式）
pub fn build_long_name(stat: &VfsStat, name: &str) -> String {
    let file_type = if stat.is_dir { 'd' } else { '-' };
    let perms = format_permissions(stat.mode & 0o777);
    let link_count = if stat.is_dir { 3 } else { 1 };
    let size = stat.size;
    let mtime = match stat.mtime.duration_since(std::time::UNIX_EPOCH) {
        Ok(d) => {
            let secs = d.as_secs();
            format_timestamp(secs)
        }
        Err(_) => "Jan  1  1970".to_string(),
    };

    format!(
        "{}{} {} {} {} {} {} {}",
        file_type, perms, link_count, stat.uid, stat.gid, size, mtime, name
    )
}

fn format_permissions(mode: u32) -> String {
    let rwx = |n: u32| -> String {
        let r = if n & 4 != 0 { 'r' } else { '-' };
        let w = if n & 2 != 0 { 'w' } else { '-' };
        let x = if n & 1 != 0 { 'x' } else { '-' };
        format!("{}{}{}", r, w, x)
    };

    format!(
        "{}{}{}",
        rwx((mode >> 6) & 7),
        rwx((mode >> 3) & 7),
        rwx(mode & 7)
    )
}

fn format_timestamp(secs: u64) -> String {
    let datetime = match chrono::DateTime::from_timestamp(secs as i64, 0) {
        Some(dt) => dt,
        None => return "Jan  1  1970".to_string(),
    };
    let now = chrono::Utc::now();
    if datetime.year() == now.year() {
        datetime.format("%b %e %H:%M").to_string()
    } else {
        datetime.format("%b %e  %Y").to_string()
    }
}