use std::cmp::Ordering;
use std::env;
use std::path::Path;
use std::thread;
use std::time::Duration;
use std::time::Instant;

use thirtyfour_sync::WebDriverCommands;

mod conf;
use conf::Conf;

mod job;
use job::Job;

struct ThreadJob {
    job: Job,
    handle: Option<
            std::thread::JoinHandle<
                    Result<String, &'static str>
                    >
            >,
    last_result: Option<String>,
}

impl ThreadJob {
    fn lru_not_running(&self, b: &ThreadJob) -> Option<Ordering> {
        // the "greater" value is one that is running, but we
        // don't recheck the thread state every time. If there's
        // a handle that isn't none, assume it's running.
        if self.handle.is_some() != b.handle.is_some() {
            if self.handle.is_some() {
                return Some(Ordering::Greater);
            }
            else {
                return Some(Ordering::Less);
            }
        }
        return self.job.last_run.partial_cmp(&b.job.last_run);
    }
}

fn verify_directory(dir: &Path) -> bool {
    let md = match std::fs::metadata(&dir) {
        Err(why) => {
            println!("Cannot stat directory '{}': {}", dir.display(), why);
            return false;
        },
        Ok(val) => val,
    };
    if !md.is_dir() {
        println!("Output directory '{}' is not a directory", dir.display());
        return false;
    }
    if md.permissions().readonly() {
        println!("Output directory '{}' is read-only", dir.display());
        return false;
    }
    return true;
}

fn main() {
    let mut conf = Conf::get_default_conf();
    conf.update_from_file(Path::new("/etc/haunter/haunter.conf"));

    let mut args = env::args();
    while let Some(arg) = args.next() {
        if arg.eq("-f") {
            match args.next() {
                Some(file) => conf.update_from_file(Path::new(&file)),
                _ => {println!("Missing argument after '-f'"); std::process::exit(1);},
            };
        }
    }

    if !verify_directory(&conf.output_dir) {
        println!("Output directory unusable, aborting");
        std::process::exit(1);
    }
    if !verify_directory(&conf.job_dir) {
        println!("Output job unusable, aborting");
        std::process::exit(1);
    }

    let mut jobs: Vec<ThreadJob> = Vec::new();

    // Load all jobs from job directory
    let job_dir = conf.job_dir.clone();
    for entry in std::fs::read_dir(job_dir).expect("Failed to iterate over job directory") {
        let _entry = match entry {
            Err(why) => {
                println!("Skipping '{}': Error reading file in job directory", why);
                continue;
            },
            Ok(value) => value,
        };
        let md = _entry.metadata().expect("Failed to read file metadata");
        if !md.is_file() {
            println!("Skipping '{}': not a file", _entry.path().display());
            continue;
        }
        match _entry.path().extension() {
            Some(x) => {
                if ! "job".eq(x) {
                    println!("Skipping '{}': does not have '.job' extension",
                             _entry.path().display());
                    continue;
                }
            },
            None => {
                println!("Skipping '{}': does not have '.job' extension",
                         _entry.path().display());
                continue;
            }
        };

        let job = match Job::from_file(&_entry.path(), &conf) {
            Err(why) => {
                println!("Failed to load job from '{}': {}", _entry.path().display(), why);
                continue;
            },
            Ok(value) => value,
        };
        jobs.push(ThreadJob {
            job: job,
            handle: None,
            last_result: None,
        });
    }

    let max_running_tasks = 5;
    loop {
        let mut running_tasks = 0;
        for tj in jobs.iter_mut().filter(|job| job.handle.is_some()) {
            // Check if the task is done
            if tj.handle.is_some() && tj.handle.as_ref().unwrap().is_finished() {
                let duration = Instant::now().duration_since(tj.job.last_run.unwrap());
                tj.job.last_run = Some(Instant::now());
                let source = tj.handle.take().unwrap().join();
                if source.is_err() {
                    println!("Error for job '{}': {:?}", tj.job.url, source);
                    tj.handle = None;
                    continue;
                }
                let fragment = scraper::Html::parse_document(source.unwrap().unwrap().as_str());
                let selector = scraper::Selector::parse(&tj.job.selector.as_str()).expect("Failed to parse selector");
                let mut result = String::from("");
                for element in fragment.select(&selector) {
                    result.push_str(element.inner_html().as_str());
                }
                println!("Job for '{}' took about {}s", tj.job.url, duration.as_secs());
                if tj.last_result.is_none() {
                    println!("New result for job: '{}'\n", tj.job.url);
                    let diff = prettydiff::diff_lines(
                        "", result.as_str());
                    tj.job.update(result.as_str(), diff.to_string().as_str());
                    tj.last_result = Some(result);
                }
                else {
                    if tj.last_result.as_ref().unwrap().ne(&result) {
                        println!("Change detected for job '{}'", tj.job.url);
                        let diff = prettydiff::diff_lines(
                            tj.last_result.as_ref().unwrap(), result.as_str());
                        tj.job.update(result.as_str(), diff.to_string().as_str());
                        tj.last_result = Some(result);
                    }
                }
                tj.handle = None;
            }
            else if tj.handle.is_some() {
                running_tasks += 1;
            }
        }
        while running_tasks < max_running_tasks {
            // Sort by least recently run
            // According to the docs, unstable_by is preferred for speed +
            // reduced memory allocations, but doesn't guarantee order of
            // equal elements.
            jobs.sort_unstable_by(|a, b| a.lru_not_running(b).unwrap());
            for tj in jobs.iter_mut() {
                let should_run_by_time = tj.job.last_run.is_some() && Instant::now().duration_since(tj.job.last_run.unwrap()).ge(&tj.job.every);
                if tj.handle.is_none() && (should_run_by_time || tj.job.last_run.is_none()) {
                    let driver = conf.driver_url.clone();
                    let url = tj.job.url.clone();
                    tj.handle = Some(thread::spawn(move || {
                        return get_source(driver.as_str(), url.as_str());
                    }));
                    println!("Started thread for '{}'", tj.job.url);
                    tj.job.last_run = Some(Instant::now());
                    running_tasks += 1;
                    if running_tasks >= max_running_tasks {
                        break;
                    }
                }
            }
            break;
        }

        std::thread::sleep(Duration::new(1, 0));
    }
}

fn get_source(driver: &str, url: &str) -> Result<String, &'static str> {
    // The firefox driver seems to crash less often than the chrome driver.
    let caps = thirtyfour_sync::DesiredCapabilities::firefox();
    let driver = thirtyfour_sync::WebDriver::new(driver, &caps).expect("failed to get driver");
    driver.get(url).expect("failed to get url");
    let source = driver.page_source().expect("failed to get page source");
    driver.quit().expect("failed to close session");
    return Ok(source);
}

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

    use tempfile;

    #[test]
    fn verify_directory_exists_but_is_file() {
        let tf = tempfile::NamedTempFile::new().unwrap();
        assert!(!verify_directory(tf.path()));
    }

    #[test]
    fn verify_directory_does_not_exist() {
        assert!(!verify_directory(Path::new("/fake/path/that/does/not/exist")));
    }

    #[test]
    fn verify_directory_exists() {
        let tf = tempfile::tempdir().unwrap();
        assert!(verify_directory(tf.path()));
    }

    #[test]
    fn verify_directory_exists_but_is_not_writable() {
        let tf = tempfile::tempdir().unwrap();
        let md = std::fs::metadata(&tf.path()).unwrap();
        let mut perms = md.permissions();
        perms.set_readonly(true);
        std::fs::set_permissions(&tf.path(), perms).expect("Failed to set temp dir read-only");
        let result = verify_directory(tf.path());
        perms = md.permissions();
        perms.set_readonly(false);
        std::fs::set_permissions(&tf.path(), perms).expect("Failed to set temp dir writable");
        assert!(!result);
    }
}