use anyhow::{Context, Result};
use clap::{Parser, Subcommand};
use rand::prelude::IndexedRandom;
use reqwest;
use std::{
    string::String,
};
use std::fs::File;
use std::io::Write;

mod config;
mod fetch;
mod parse;

// Setup the command line options

#[derive(Parser)]
#[command(about = "Retrieve the latest UserAgent strings", long_about=None, arg_required_else_help = true, after_help = "This is very specific to the website's HTML.\nIf it changes, this program might no longer work.")]
struct Cli {
    // Update UserAgent versions
    // #[arg(short, long, action=clap::ArgAction::SetTrue)]
    // update: bool,
    #[command(subcommand)]
    command: Option<Commands>,
}

#[derive(Subcommand)]
enum Commands {
    /// Display the latest UserAgents
    Display {},
    /// Fetch the latest UserAgents
    Fetch {},
}

/// Configuration filename
const CONFIG_FILE: &str = "latest.config";

const FIREFOX_URL: &str = "https://www.whatismybrowser.com/guides/the-latest-user-agent/firefox";
const GCHROME_URL: &str = "https://www.whatismybrowser.com/guides/the-latest-user-agent/chrome";

fn random_user_agent(config: &config::Config) -> String {
    // Pick a random user_agent, or default to something "sane"...
    if config.user_agents.len() == 0 {
        // No sensible defaults.
        return String::from(
            "Mozilla/5.0 (X11; Linux x86_64; rv:135.0) Gecko/20100101 Firefox/135.0",
        );
    }
    // Ok, do this!
    config.user_agents.choose(&mut rand::rng()).unwrap().clone()
}

fn save_html(filename: &str, html: &str) -> Result<()> {
    let mut file = File::create(filename)
        .with_context(|| format!("Failed to write file [{:?}].", filename))?;

    file.write_all(html.as_bytes())
        .with_context(|| format!("Failed to write all to [{:?}].", filename))?;
    Ok(())
}

fn main() -> Result<()> {
    let mut config = config::read_config(CONFIG_FILE)?;

    let cli = Cli::parse();

    match &cli.command {
        Some(Commands::Fetch {}) => {
            let ua = random_user_agent(&config);
            let client = reqwest::blocking::Client::builder()
                .user_agent(&ua)
                .build()?;

            let result = fetch::fetch(&client, FIREFOX_URL)?;
            let filename = fetch::filename_from_url(FIREFOX_URL)?;
            save_html(&filename, &result)?;

            let mut agents = parse::find_useragents(&result)?;
            config.user_agents.clear();
            config.user_agents.append(&mut agents);

            let result = fetch::fetch(&client, GCHROME_URL)?;
            let filename = fetch::filename_from_url(GCHROME_URL)?;
            save_html(&filename, &result)?;

            agents = parse::find_useragents(&result)?;
            config.user_agents.append(&mut agents);
            config::write_config(CONFIG_FILE, &config)?;
            println!("Ok! {} agents found.", config.user_agents.len());
        }

        Some(Commands::Display {}) => {
            println!("Display...");
            for ua in config.user_agents {
                println!("  {}", ua);
            }

            return Ok(());
        }

        None => {
            println!("I didn't see a command.  Displaying help.\n");
            let _show_help: Cli = Cli::parse_from(["--help"]);
        }
    }

    Ok(())
}