use std::fs;
use std::path::PathBuf;
use tauri::Manager;

#[derive(serde::Serialize)]
pub struct BookSummary {
    id: String,
    title: String,
    author: String,
}

fn library_dir(app: &tauri::AppHandle) -> Result<PathBuf, String> {
    let dir = app
        .path()
        .app_data_dir()
        .map_err(|e| e.to_string())?
        .join("library");
    fs::create_dir_all(&dir).map_err(|e| e.to_string())?;
    Ok(dir)
}

#[tauri::command]
pub fn list_books(app: tauri::AppHandle) -> Result<Vec<BookSummary>, String> {
    let dir = library_dir(&app)?;
    let mut books = Vec::new();
    for entry in fs::read_dir(&dir).map_err(|e| e.to_string())? {
        let path = match entry {
            Ok(entry) => entry.path(),
            Err(_) => continue,
        };
        if path.extension().and_then(|e| e.to_str()) != Some("margin") {
            continue;
        }
        let contents = match fs::read_to_string(&path) {
            Ok(contents) => contents,
            Err(_) => continue,
        };
        let value: serde_json::Value = match serde_json::from_str(&contents) {
            Ok(value) => value,
            Err(_) => continue,
        };
        let id = value.get("id").and_then(|v| v.as_str()).unwrap_or("");
        if id.is_empty() {
            continue;
        }
        let metadata = value.get("metadata");
        let title = metadata
            .and_then(|m| m.get("title"))
            .and_then(|v| v.as_str())
            .unwrap_or("Untitled")
            .to_string();
        let author = metadata
            .and_then(|m| m.get("author"))
            .and_then(|v| v.as_str())
            .unwrap_or("")
            .to_string();
        books.push(BookSummary {
            id: id.to_string(),
            title,
            author,
        });
    }
    Ok(books)
}

#[tauri::command]
pub fn load_book(app: tauri::AppHandle, id: String) -> Result<String, String> {
    let path = library_dir(&app)?.join(format!("{id}.margin"));
    fs::read_to_string(&path).map_err(|e| e.to_string())
}

#[tauri::command]
pub fn save_book(app: tauri::AppHandle, id: String, contents: String) -> Result<(), String> {
    let path = library_dir(&app)?.join(format!("{id}.margin"));
    fs::write(&path, contents).map_err(|e| e.to_string())
}

#[tauri::command]
pub fn delete_book(app: tauri::AppHandle, id: String) -> Result<(), String> {
    let path = library_dir(&app)?.join(format!("{id}.margin"));
    if path.exists() {
        fs::remove_file(&path).map_err(|e| e.to_string())?;
    }
    Ok(())
}