use std::{
    collections::HashMap,
    marker::PhantomData,
};

use postgres::Client;

use cqrs_es2::{
    AggregateContext,
    AggregateError,
    EventEnvelope,
    IAggregate,
    IEventStore,
};

use crate::sql::{
    INSERT_EVENT,
    SELECT_EVENTS,
};

/// Storage engine using an Postgres backing. This is the only
/// persistent store currently provided.
pub struct EventStore<A: IAggregate> {
    conn: Client,
    _phantom: PhantomData<A>,
}

impl<A: IAggregate> EventStore<A> {
    /// Creates a new `EventStore` from the provided database
    /// connection.
    pub fn new(conn: Client) -> Self {
        EventStore {
            conn,
            _phantom: PhantomData,
        }
    }
}

impl<A: IAggregate> IEventStore<A> for EventStore<A> {
    fn load(
        &mut self,
        aggregate_id: &str,
    ) -> Vec<EventEnvelope<A>> {
        let agg_type = A::aggregate_type();
        let id = aggregate_id.to_string();

        let mut result = Vec::new();

        match self
            .conn
            .query(SELECT_EVENTS, &[&agg_type, &id])
        {
            Ok(rows) => {
                for row in rows.iter() {
                    let aggregate_id: String =
                        row.get("aggregate_id");
                    let s: i64 = row.get("sequence");
                    let sequence = s as usize;

                    let payload: A::Event =
                        match serde_json::from_value(
                            row.get("payload"),
                        ) {
                            Ok(payload) => payload,
                            Err(err) => {
                                panic!(
                                    "bad payload found in events \
                                     table for aggregate id {} with \
                                     error: {}",
                                    &id, err
                                );
                            },
                        };

                    let event = EventEnvelope::new(
                        aggregate_id,
                        sequence,
                        payload,
                    );

                    result.push(event);
                }
            },
            Err(e) => {
                println!("{:?}", e);
            },
        }

        result
    }

    fn load_aggregate(
        &mut self,
        aggregate_id: &str,
    ) -> AggregateContext<A> {
        let committed_events = self.load(aggregate_id);

        let mut aggregate = A::default();
        let mut current_sequence = 0;

        for envelope in committed_events {
            current_sequence = envelope.sequence;
            let event = envelope.payload;
            aggregate.apply(&event);
        }

        AggregateContext {
            aggregate_id: aggregate_id.to_string(),
            aggregate,
            current_sequence,
        }
    }

    fn commit(
        &mut self,
        events: Vec<A::Event>,
        context: AggregateContext<A>,
        metadata: HashMap<String, String>,
    ) -> Result<Vec<EventEnvelope<A>>, AggregateError> {
        let agg_type = A::aggregate_type().to_string();
        let aggregate_id = context.aggregate_id.as_str();
        let current_sequence = context.current_sequence;

        let wrapped_events = self.wrap_events(
            aggregate_id,
            current_sequence,
            events,
            metadata,
        );

        let mut trans = match self.conn.transaction() {
            Ok(t) => t,
            Err(err) => {
                return Err(AggregateError::TechnicalError(
                    err.to_string(),
                ));
            },
        };

        for event in &wrapped_events {
            let id = context.aggregate_id.clone();
            let sequence = event.sequence as i64;

            let payload = match serde_json::to_value(&event.payload) {
                Ok(payload) => payload,
                Err(err) => {
                    panic!(
                        "bad payload found in events table for \
                         aggregate id {} with error: {}",
                        &id, err
                    );
                },
            };

            let metadata = match serde_json::to_value(&event.metadata)
            {
                Ok(metadata) => metadata,
                Err(err) => {
                    panic!(
                        "bad metadata found in events table for \
                         aggregate id {} with error: {}",
                        &id, err
                    );
                },
            };

            match trans.execute(
                INSERT_EVENT,
                &[
                    &agg_type, &id, &sequence, &payload, &metadata,
                ],
            ) {
                Ok(_) => {},
                Err(err) => {
                    match err.code() {
                        None => {},
                        Some(state) => {
                            if state.code() == "23505" {
                                return Err(
                                    AggregateError::TechnicalError(
                                        "optimistic lock error"
                                            .to_string(),
                                    ),
                                );
                            }
                        },
                    }
                    panic!(
                        "unable to insert event table for aggregate \
                         id {} with error: {}\n  and payload: {}",
                        &id, err, &payload
                    );
                },
            };
        }

        match trans.commit() {
            Ok(_) => Ok(wrapped_events),
            Err(err) => {
                Err(AggregateError::TechnicalError(
                    err.to_string(),
                ))
            },
        }
    }
}