/**
 * Date and time representation in the stream.
 *
 * SPDX-FileCopyrightText: 2023 Eilertsens Kodeknekkeri
 * SPDX-FileCopyrightText: 2023 Harald Eilertsen <haraldei@anduin.net>
 *
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

use chrono::NaiveDateTime;
use serde::Deserialize;

/**
 * Handle date and time.
 *
 * This is mainly a wrapper around the chrono::NaiveDateTime struct,
 * as the date and time returned by the json data from the zot stream
 * API's does not contain any timezone information.
 */
#[derive(Debug, PartialEq)]
pub struct DateTime {
    datetime: Option<NaiveDateTime>
}

/*
 * Implement Display for the DateTime type, so that it will display
 * using the correct time and date format by default.
 */
impl std::fmt::Display for DateTime {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self.datetime {
            Some(dt) => write!(f, "{}", dt.format("%Y-%m-%d %H:%M:%S")),
            None => write!(f, "0000-00-00 00:00:00"),
        }
    }
}

/*
 * Since the date and time format returned in the json from the
 * stream API, does not conform to the RFC3339 format expected by
 * the default chrono deserializer, we have to implement our own
 * deserializer.
 */
impl<'de> Deserialize<'de> for DateTime {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where
            D: serde::de::Deserializer<'de>,
    {
        Ok(deserializer.deserialize_str(DateTimeVisitor)?)
    }
}

struct DateTimeVisitor;

impl<'de> serde::de::Visitor<'de> for DateTimeVisitor {
    type Value = DateTime;

    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(formatter, "a date and time formatted string")
    }

    fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
        where
            E: serde::de::Error,
    {
        let datetime = if s == "0000-00-00 00:00:00" {
            None
        } else {
            Some(NaiveDateTime::parse_from_str(s, "%Y-%m-%d %H:%M:%S")
                .map_err(|_| E::custom(format!("invalid date time format: {}", s)))?)
        };

        Ok(Self::Value{ datetime })
    }
}

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

    #[test]
    fn test_deserialize_datetime() {
        let tests = vec![
            r#""0000-00-00 00:00:00""#,
            r#""2016-12-17 13:37:00""#,
        ];

        for test in tests {
            let datetime: DateTime = serde_json::from_str(test).unwrap();
            assert_eq!(test.trim_matches('"'), datetime.to_string());
        }
    }
}