use crate::config::{ListOptions, CONFIG};
use crate::util;
use anyhow::Result;
use glob::glob;
use serde::{Deserialize, Deserializer, Serialize};
use std::io::prelude::*;
use std::os::unix::fs::symlink;
use std::{
    fs::{remove_file, File},
    path::PathBuf,
};
use structopt::StructOpt;

#[derive(Serialize, Deserialize, StructOpt, Debug, Clone)]
pub struct Course {
    pub name: String,
    #[serde(skip)]
    #[structopt(skip)]
    pub path: PathBuf,
    short: String,
    #[serde(default)]
    #[structopt(long)]
    url: Option<String>,
    #[serde(default)]
    #[structopt(long)]
    moodle: Option<String>,
    #[serde(deserialize_with = "string_or_vec", alias = "semester")]
    semesters: Vec<String>,
    #[structopt(skip)]
    meetings: Option<Vec<Meeting>>,
}

#[derive(Serialize, Deserialize, StructOpt, Debug, Clone)]
pub struct Meeting {
    pub name: String,
    pub url: String,
}

impl Course {
    pub fn current() -> Self {
        Self::from_path(&CONFIG.link_path)
    }

    // TODO: make this the single method to read a Course
    pub fn from_path(path: impl AsRef<std::path::Path> + Clone) -> Self {
        // TODO: make "course.toml" a *documented* magic value or configurable
        let path: PathBuf = path.as_ref().join("course.toml");
        let course_string = std::fs::read_to_string(&path);
        if let Ok(course_string) = course_string {
            let mut course: Course = toml::from_str(&course_string).unwrap_or_else(|e| {
                panic!("Error while parsing course at {:?} \n{}", &path, e);
            });
            course.path = path;
            course
        } else {
            panic!(
                "Error while reading course at {:?}\n{}",
                path,
                course_string.unwrap_err()
            );
        }
    }

    /// Get a reference to the course's semesters.
    pub fn semesters(&self) -> &Vec<String> {
        &self.semesters
    }

    /// Get a reference to the course's semesters.
    pub fn semesters_mut(&mut self) -> &mut Vec<String> {
        &mut self.semesters
    }

    /// Check if course is part of current semester
    pub fn is_current(&self) -> bool {
        self.semesters()
            .iter()
            .any(|x| x == &util::get_current_semester())
    }

    pub fn meetings(&self) -> &Option<Vec<Meeting>> {
        &self.meetings
    }

    pub fn set(&self) -> Result<()> {
        // TODO: make sure this is actually a link, and we are not removing some other file of the user
        remove_file(&CONFIG.link_path)?;
        symlink(&self.path, &CONFIG.link_path)?;
        Ok(())
    }

    pub fn list(options: &ListOptions) -> Result<CourseList> {
        let mut courses: Vec<Course> = vec![];
        let pattern = [
            CONFIG.files_root.canonicalize().unwrap().to_str().unwrap(),
            "/*/course.toml",
        ]
        .concat();
        let mut handle;
        for entry in glob(pattern.as_str()).unwrap() {
            let path = entry.unwrap();
            let mut coursestring = String::new();
            handle = File::open(&path).unwrap();
            handle.read_to_string(&mut coursestring).unwrap();
            let mut course: Course = toml::from_str(&coursestring)?;
            course.path = path.parent().unwrap().to_path_buf();
            if options.all || course.is_current() {
                courses.push(course);
            }
        }

        Ok(CourseList::new(courses))
    }

    pub fn check(list_options: &ListOptions) -> Result<()> {
        let mut problematic_course_count = 0;
        let toml_list = Self::list(list_options)?;
        println!("Checking course.toml's");
        for c in toml_list.iter() {
            let mut problems = Vec::new();
            if c.name.is_empty() {
                problems.push("     Name is empty")
            }
            if c.short.is_empty() {
                problems.push("     Short is empty")
            }
            if c.url.is_none() {
                problems.push("     No URL (set empty string to mark nonexistant website)")
            }
            if c.moodle.is_none() {
                problems.push("     No Moodle-URL (set empty string to mark nonexistant website)")
            }
            if c.semesters.is_empty() {
                problems.push("     Course is not in any semesters")
            }
            if !problems.is_empty() {
                eprintln!(
                    "Found {} problems with {}/course.toml",
                    problems.len(),
                    c.path.to_str().unwrap()
                );
                for p in problems {
                    eprintln!("{}", p)
                }
                problematic_course_count += 1;
            } else {
                println!("No problems found with {:?}", c.path);
            }
        }
        println!("Found {} courses with problems", problematic_course_count);
        Ok(())
    }
}

fn string_or_vec<'de, D>(deserializer: D) -> Result<Vec<String>, D::Error>
where
    D: Deserializer<'de>,
{
    #[derive(Deserialize)]
    #[serde(untagged)]
    enum StringOrVec {
        String(String),
        Vec(Vec<String>),
    }

    match StringOrVec::deserialize(deserializer)? {
        StringOrVec::String(s) => Ok(vec![s]),
        StringOrVec::Vec(vec) => Ok(vec),
    }
}
pub struct CourseList(Vec<Course>);

impl std::fmt::Display for CourseList {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for c in &self.0 {
            writeln!(f, "{}", c)?;
        }
        Ok(())
    }
}

impl CourseList {
    pub fn new(inner: Vec<Course>) -> Self {
        CourseList(inner)
    }

    pub fn iter(&self) -> std::slice::Iter<Course> {
        self.0.iter()
    }

    pub fn get(&self, element: usize) -> Option<&Course> {
        self.0.get(element)
    }
}

impl std::fmt::Display for Course {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.name)
    }
}

// #[derive(Debug)]
// pub enum ParseSemesterError{
//     ParseIntError(ParseIntError),
//     NoFormatFound,
// }

// impl std::fmt::Display for ParseSemesterError{
//     fn fmt(&self, _f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
//         todo!()
//     }
// }

// impl std::convert::From<ParseIntError> for ParseSemesterError{
//     fn from(e: ParseIntError) -> Self {
//         Self::ParseIntError(e)
//     }
// }