use std::{fs, io::Write, path::PathBuf};
use clap::Parser;
use serde::Deserialize;
use regex::Regex;
use tempfile::tempdir;
use reqwest::blocking::Client;

/// ICS zu CalDAV Uploader
#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
struct Args {
    /// Pfad zur Konfigurationsdatei (config.json)
    #[arg(short, long, value_name = "FILE")]
    config: PathBuf,
}

#[derive(Deserialize)]
struct Config {
    caldav_base_url: String,
    caldav_username: String,
    caldav_password: String,
    calendars: Vec<CalendarEntry>,
}

#[derive(Deserialize)]
struct CalendarEntry {
    name: String,
    ics: String,
}

fn main() -> anyhow::Result<()> {
    let args = Args::parse();

    let config_data = fs::read_to_string(&args.config)?;
    let config: Config = serde_json::from_str(&config_data)?;

    let tmp_dir = tempdir()?;
    let client = Client::builder()
        .timeout(std::time::Duration::from_secs(60))
        .build()?;

    for cal in &config.calendars {
        println!("INFO: Lade ICS von: {}", cal.ics);
        let ics_path = tmp_dir.path().join(format!("{}.ics", cal.name));
        let response = client.get(&cal.ics).send()?;
        if !response.status().is_success() {
            eprintln!("WARNING: Fehler beim Herunterladen von {}", cal.ics);
            continue;
        }
        let ics_content = response.text()?;
        fs::write(&ics_path, &ics_content)?;

        let caldav_url = format!("{}/{}", config.caldav_base_url.trim_end_matches('/'), cal.name);
        println!("INFO: Zerlege Datei: {:?}", ics_path);

        let vevent_blocks = split_vevents(&ics_content);
        for vevent in vevent_blocks {
            if let Some(uid) = extract_uid(&vevent) {
                let safe_uid = sanitize_filename(&uid);
                let event_path = tmp_dir.path().join(format!("{}.ics", safe_uid));
                let mut event_file = fs::File::create(&event_path)?;

                writeln!(event_file, "BEGIN:VCALENDAR")?;
                writeln!(event_file, "VERSION:2.0")?;
                writeln!(event_file, "PRODID:-//calendar script//EN")?;
                writeln!(event_file, "{}", vevent.trim())?;
                writeln!(event_file, "END:VCALENDAR")?;

                println!("INFO: Lade UID={} → {}/{}.ics", safe_uid, caldav_url, safe_uid);
                let put_url = format!("{}/{}.ics", caldav_url, safe_uid);

                let body = fs::read(&event_path)?;
                let put_response = client
                    .put(&put_url)
                    .basic_auth(&config.caldav_username, Some(&config.caldav_password))
                    .header("Content-Type", "text/calendar; charset=utf-8")
                    .body(body)
                    .send()?;

                println!("→ HTTP-Code: {}", put_response.status());
            }
        }
    }

    Ok(())
}

fn split_vevents(ics: &str) -> Vec<String> {
    let mut vevents = Vec::new();
    let mut in_event = false;
    let mut buffer = String::new();

    for line in ics.lines() {
        if line.trim() == "BEGIN:VEVENT" {
            in_event = true;
            buffer.clear();
        }

        if in_event {
            buffer.push_str(line);
            buffer.push('\n');
        }

        if line.trim() == "END:VEVENT" && in_event {
            in_event = false;
            vevents.push(buffer.clone());
        }
    }

    vevents
}

fn extract_uid(event: &str) -> Option<String> {
    for line in event.lines() {
        if line.starts_with("UID:") {
            return Some(line.trim_start_matches("UID:").trim().to_string());
        }
    }
    None
}

fn sanitize_filename(name: &str) -> String {
    let re = Regex::new(r"[^a-zA-Z0-9._-]").unwrap();
    re.replace_all(name, "_").to_string()
}