use std::collections::{HashMap, HashSet};
use std::fmt::Write;
use std::str::FromStr;
use chrono::{DateTime, NaiveDate, NaiveDateTime, Local, Utc};

mod tokenizer;
mod parser;
pub use parser::Parser;

pub trait GetValue<'a, R: 'a> {
    fn get(&'a self, key: &'_ str) -> Option<R>;
}

pub type Props = Vec<(String, String)>;

#[derive(Debug, PartialEq)]
pub struct Object {
    pub name: String,
    pub content: HashMap<String, Vec<(Props, String)>>,
    pub children: Vec<Box<Object>>,
}

impl<'a> GetValue<'a, &'a str> for Object {
    fn get(&'a self, key: &'_ str) -> Option<&'a str> {
        self.content.get(key)
            .and_then(|pairs| pairs.first().map(|(_props, value)| value.as_str()))
    }
}

impl<'a> GetValue<'a, &'a (Props, String)> for Object {
    fn get(&'a self, key: &'_ str) -> Option<&'a (Props, String)> {
        self.content.get(key)
            .and_then(|pairs| pairs.first())
    }
}

impl<'a> GetValue<'a, &'a [(Props, String)]> for Object {
    fn get(&'a self, key: &'_ str) -> Option<&'a [(Props, String)]> {
        self.content.get(key)
            .map(|data| data.as_slice())
    }
}

impl<'a> GetValue<'a, String> for Object {
    fn get(&self, key: &'_ str) -> Option<String> {
        self.content.get(key)
            .and_then(|pairs| pairs.first().map(|(_props, value)| value.clone()))
    }
}

// TODO: TZID, offset
impl<'a> GetValue<'a, Timestamp> for Object {
    fn get(&self, key: &'_ str) -> Option<Timestamp> {
        let s = self.get(key)?;
        Timestamp::from_str(s)
            .map_err(|e| println!("Cannot parse date: {:?}", e))
            .ok()
    }
}

impl Object {
    pub fn fmt_rrule(&self) -> Result<String, std::fmt::Error> {
        let rrule_keys = [
            "DTSTART",
            "RRULE", "RDATE",
            "EXRULE", "EXDATE",
        ].iter().cloned().collect::<HashSet<_>>();

        let mut s = String::new();
        for (name, values) in &self.content {
            if ! rrule_keys.contains(name.as_str()) {
                continue;
            }
            for (props, value) in values {
                write!(s, "{}", name)?;
                for (key, prop) in props {
                    write!(s, ";{}={}", key, prop)?;
                }
                writeln!(s, ":{}", value)?;
            }
        }
        Ok(s)
    }
}

#[derive(Debug, Clone)]
pub enum Timestamp {
    Date(NaiveDate),
    DateTime(NaiveDateTime),
}

impl FromStr for Timestamp {
    type Err = String;

    fn from_str(s: &'_ str) -> Result<Self, Self::Err> {
        NaiveDateTime::parse_from_str(s, "%Y%m%dT%H%M%SZ")
            .map(|time| DateTime::<Utc>::from_utc(time, Utc)
                 .with_timezone(&Local)
                 .naive_local()
            )
            .or_else(|_| NaiveDateTime::parse_from_str(s, "%Y%m%dT%H%M%S"))
            .map(Timestamp::DateTime)
            .or_else(|_|
                 NaiveDate::parse_from_str(s, "%Y%m%d")
                 .map(Timestamp::Date)
            )
            .map_err(|e| format!("Cannot parse date: {:?}", e))
    }
}

impl Timestamp {
    pub fn or_hms(self, hour: u32, min: u32, sec: u32) -> NaiveDateTime {
        match self {
            Timestamp::Date(date) => date.and_hms(hour, min, sec),
            Timestamp::DateTime(date_time) => date_time,
        }
    }
}