//! Files the viewer makes for you (report PDFs). They go to the
//! Downloads folder, never into the books: the viewer stays read-only.

use std::path::{Path, PathBuf};

/// Where saved files go: `$XDG_DOWNLOAD_DIR`, else `~/Downloads`, else
/// the home directory.
pub fn downloads_dir() -> PathBuf {
    if let Some(d) = std::env::var_os("XDG_DOWNLOAD_DIR").map(PathBuf::from)
        && d.is_dir()
    {
        return d;
    }
    let home = std::env::var_os("HOME")
        .or_else(|| std::env::var_os("USERPROFILE"))
        .map(PathBuf::from)
        .unwrap_or_else(|| PathBuf::from("."));
    let d = home.join("Downloads");
    if d.is_dir() { d } else { home }
}

/// `name` made safe as a file name on every platform.
pub fn file_name(name: &str, ext: &str) -> String {
    let clean: String = name
        .chars()
        .map(|c| match c {
            '/' | '\\' | ':' | '*' | '?' | '"' | '<' | '>' | '|' => '-',
            c if c.is_control() => ' ',
            c => c,
        })
        .collect();
    format!("{}.{ext}", clean.trim())
}

/// Write `bytes` to the downloads folder as `name.ext` (replacing a file
/// of that name: the same report renders the same bytes) and open it with
/// the system's viewer.
pub fn save_and_open(name: &str, ext: &str, bytes: &[u8]) -> Result<PathBuf, String> {
    let path = downloads_dir().join(file_name(name, ext));
    std::fs::write(&path, bytes).map_err(|e| format!("{}: {e}", path.display()))?;
    open(&path);
    Ok(path)
}

/// Open a file with whatever the desktop uses for its type. Best effort:
/// the file is saved either way.
fn open(path: &Path) {
    #[cfg(target_os = "macos")]
    let cmd = std::process::Command::new("open").arg(path).spawn();
    #[cfg(target_os = "windows")]
    let cmd = std::process::Command::new("cmd")
        .args(["/C", "start", ""])
        .arg(path)
        .spawn();
    #[cfg(not(any(target_os = "macos", target_os = "windows")))]
    let cmd = std::process::Command::new("xdg-open").arg(path).spawn();
    let _ = cmd;
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn file_names_are_safe() {
        assert_eq!(
            file_name("Acme LLC — Profit and loss — Jan 1/2026: draft", "pdf"),
            "Acme LLC — Profit and loss — Jan 1-2026- draft.pdf"
        );
    }
}