use std::io::Write;

use chrono::{DateTime, Utc, Local, LocalResult, TimeZone};
use ansi_term::Color::Yellow;

use crate::error::{Error, Result};
use crate::models::Entry;
use crate::database::{Database, DBVersion};

fn local_to_utc(t: DateTime<Utc>) -> Result<DateTime<Utc>> {
    let local_time = match Local.from_local_datetime(&t.naive_utc()) {
        LocalResult::None => return Err(Error::NoneLocalTime(t.naive_utc().to_string())),
        LocalResult::Single(t) => t,
        LocalResult::Ambiguous(t1, t2) => return Err(Error::AmbiguousLocalTime {
            orig: t.naive_utc().to_string(),
            t1: t1.naive_local(),
            t2: t2.naive_local(),
        }),
    };

    Ok(Utc.from_utc_datetime(&local_time.naive_utc()))
}

fn local_to_utc_vec(entries: Vec<Entry>) -> Result<Vec<Entry>> {
    entries
        .into_iter()
        .map(|e| {
            Ok(Entry {
                start: local_to_utc(e.start)?,
                end: e.end.map(|t| local_to_utc(t)).transpose()?,
                ..e
            })
        })
        .collect()
}

pub fn entries_or_warning<D: Database>(entries: Vec<Entry>, db: &D) -> Result<(Vec<Entry>, bool)> {
    if let DBVersion::Timetrap = db.version()? {
        // this indicates that times in the database are specified in the
        // local time and need to be converted to utc before displaying

        Ok((local_to_utc_vec(entries)?, true))
    } else {
        Ok((entries, false))
    }
}

pub fn warn_if_needed<E: Write>(err: &mut E, needs_warning: bool) -> Result<()> {
    if needs_warning {
        writeln!(
            err,
            "{} You are using the old timetrap format, it is advised that \
            you update your database using t migrate",
            Yellow.bold().paint("[WARNING]"),
        )?;
    }

    Ok(())
}