use fmt::Display;
use std::cmp::Ordering;
use std::collections::{BTreeSet, HashSet};
use std::fmt;

use itertools::Either::{Left, Right};
use itertools::Itertools;
use log::{debug, error, info, trace, warn};
use nostr_sdk::{Event, EventBuilder, EventId, Kind, Tag, TagStandard, Timestamp};

use crate::helpers::some_non_empty;
use crate::kinds::{is_hashtag, PROCEDURE_KIND};

#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) struct Task {
    /// Event that defines this task
    pub(crate) event: Event,
    /// Cached sorted tags of the event with references remove - do not modify!
    pub(crate) tags: Option<BTreeSet<Tag>>,
    /// Parent task references derived from the event tags
    parents: Vec<EventId>,

    /// Reference to children, populated dynamically
    pub(crate) children: HashSet<EventId>,
    /// Events belonging to this task, such as state updates and notes
    pub(crate) props: BTreeSet<Event>,
}

impl PartialOrd<Self> for Task {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        self.event.partial_cmp(&other.event)
    }
}

impl Ord for Task {
    fn cmp(&self, other: &Self) -> Ordering {
        self.event.cmp(&other.event)
    }
}

impl Task {
    pub(crate) fn new(event: Event) -> Task {
        let (refs, tags) = event.tags.iter().partition_map(|tag| match tag.as_standardized() {
            Some(TagStandard::Event { event_id, .. }) => return Left(event_id),
            _ => Right(tag.clone()),
        });
        // Separate refs for dependencies
        Task {
            children: Default::default(),
            props: Default::default(),
            tags: Some(tags).filter(|t: &BTreeSet<Tag>| !t.is_empty()),
            parents: refs,
            event,
        }
    }

    pub(crate) fn get_id(&self) -> &EventId {
        &self.event.id
    }

    pub(crate) fn parent_id(&self) -> Option<&EventId> {
        self.parents.first()
    }

    pub(crate) fn get_title(&self) -> String {
        Some(self.event.content.trim().to_string())
            .filter(|s| !s.is_empty())
            .unwrap_or_else(|| self.get_id().to_string())
    }

    pub(crate) fn description_events(&self) -> impl Iterator<Item=&Event> + '_ {
        self.props.iter().filter_map(|event| {
            if event.kind == Kind::TextNote {
                Some(event)
            } else {
                None
            }
        })
    }

    pub(crate) fn descriptions(&self) -> impl Iterator<Item=&String> + '_ {
        self.description_events().map(|e| &e.content)
    }

    fn states(&self) -> impl Iterator<Item=TaskState> + '_ {
        self.props.iter().filter_map(|event| {
            event.kind.try_into().ok().map(|s| TaskState {
                name: some_non_empty(&event.content),
                state: s,
                time: event.created_at.clone(),
            })
        })
    }

    pub(crate) fn state(&self) -> Option<TaskState> {
        self.states().max_by_key(|t| t.time)
    }

    pub(crate) fn pure_state(&self) -> State {
        self.state().map_or(State::Open, |s| s.state)
    }

    pub(crate) fn state_or_default(&self) -> TaskState {
        self.state().unwrap_or_else(|| self.default_state())
    }

    fn default_state(&self) -> TaskState {
        TaskState {
            name: None,
            state: State::Open,
            time: self.event.created_at,
        }
    }

    fn filter_tags<P>(&self, predicate: P) -> Option<String>
    where
        P: FnMut(&&Tag) -> bool,
    {
        self.tags.as_ref().map(|tags| {
            tags.into_iter()
                .filter(predicate)
                .map(|t| format!("{}", t.content().unwrap()))
                .collect::<Vec<String>>()
                .join(" ")
        })
    }

    pub(crate) fn get(&self, property: &str) -> Option<String> {
        match property {
            "id" => Some(self.event.id.to_string()),
            "parentid" => self.parent_id().map(|i| i.to_string()),
            "state" => Some(self.state_or_default().get_label()),
            "name" => Some(self.event.content.clone()),
            "desc" => self.descriptions().last().cloned(),
            "description" => Some(self.descriptions().join(" ")),
            "hashtags" => self.filter_tags(|tag| { is_hashtag(tag) }),
            "tags" => self.filter_tags(|_| true),
            "alltags" => Some(format!("{:?}", self.tags)),
            "parents" => Some(format!("{:?}", self.parents.iter().map(|id| id.to_string()).collect_vec())),
            "props" => Some(format!(
                "{:?}",
                self.props
                    .iter()
                    .map(|e| format!("{} kind {} \"{}\"", e.created_at, e.kind, e.content))
                    .collect_vec()
            )),
            "descriptions" => Some(format!(
                "{:?}",
                self.descriptions().collect_vec()
            )),
            _ => {
                warn!("Unknown task property {}", property);
                None
            }
        }
    }
}

pub(crate) struct TaskState {
    state: State,
    name: Option<String>,
    pub(crate) time: Timestamp,
}
impl TaskState {
    pub(crate) fn get_label_for(state: &State, comment: &str) -> String {
        some_non_empty(comment).unwrap_or_else(|| state.to_string())
    }
    pub(crate) fn get_label(&self) -> String {
        self.name.clone().unwrap_or_else(|| self.state.to_string())
    }
    pub(crate) fn matches_label(&self, label: &str) -> bool {
        self.name.as_ref().is_some_and(|n| n.eq_ignore_ascii_case(label))
            || self.state.to_string().eq_ignore_ascii_case(label)
    }
}
impl Display for TaskState {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let state_str = self.state.to_string();
        write!(
            f,
            "{}",
            self.name
                .as_ref()
                .map(|s| s.trim())
                .filter(|s| !s.eq_ignore_ascii_case(&state_str))
                .map_or(state_str, |s| format!("{}: {}", self.state, s))
        )
    }
}

#[derive(Debug, Copy, Clone, PartialEq)]
pub(crate) enum State {
    Closed,
    Open,
    Procedure,
    Pending,
    Done,
}
impl TryFrom<Kind> for State {
    type Error = ();

    fn try_from(value: Kind) -> Result<Self, Self::Error> {
        match value.as_u16() {
            1630 => Ok(State::Open),
            1631 => Ok(State::Done),
            1632 => Ok(State::Closed),
            1633 => Ok(State::Pending),
            PROCEDURE_KIND => Ok(State::Procedure),
            _ => Err(()),
        }
    }
}
impl State {
    pub(crate) fn is_open(&self) -> bool {
        match self {
            State::Open | State::Procedure => true,
            _ => false,
        }
    }

    pub(crate) fn kind(&self) -> u16 {
        match self {
            State::Open => 1630,
            State::Done => 1631,
            State::Closed => 1632,
            State::Pending => 1633,
            State::Procedure => PROCEDURE_KIND,
        }
    }
}
impl From<State> for Kind {
    fn from(value: State) -> Self {
        Kind::from(value.kind())
    }
}
impl Display for State {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(self, f)
    }
}