use anyhow::Result;
use diesel::prelude::*;
use diesel::query_dsl::BelongingToDsl;

use crate::{
    models::{
        Conversation,
        Message,
        Participant,
        db::conversation::Record as ConversationRecord,
        db::participant::{
            ConversationParticipant, 
            Record as ParticipantRecord, 
            InsertableRecord as InsertableParticipantRecord
        },
        db::message::Record as MessageRecord,
    },
    schema,
};

pub struct Repository<'a> {
    connection: &'a mut SqliteConnection,
}

impl<'a> Repository<'a> {
    pub fn new(connection: &'a mut SqliteConnection) -> Self {
        Self { connection }
    }

    pub fn insert_conversation(&mut self, conversation: Conversation) -> Result<()> {
        use crate::schema::conversations::dsl::*;
        use crate::schema::participants::dsl::*;
        use crate::schema::conversation_participants::dsl::*;

        let (db_conversation, db_participants) = conversation.into();

        diesel::replace_into(conversations)
            .values(&db_conversation)
            .execute(self.connection)?;

        diesel::replace_into(participants)
            .values(&db_participants)
            .execute(self.connection)?;

        // Sqlite backend doesn't support batch insert, so we have to do this manually
        for participant in db_participants {
            let pid = participants
                .select(schema::participants::id)
                .filter(schema::participants::display_name.eq(&participant.display_name))
                .first::<i32>(self.connection)?;

            diesel::replace_into(conversation_participants)
                .values((
                    conversation_id.eq(&db_conversation.id),
                    participant_id.eq(pid),
                ))
                .execute(self.connection)?;
        }

        Ok(())
    }

    pub fn get_conversation_by_guid(&mut self, match_guid: &str) -> Result<Option<Conversation>> {
        use crate::schema::conversations::dsl::*;
        use crate::schema::participants::dsl::*;

        let result = conversations
            .find(match_guid)
            .first::<ConversationRecord>(self.connection)
            .optional()?;

        if let Some(conversation) = result {
            let db_participants = ConversationParticipant::belonging_to(&conversation)
                .inner_join(participants)
                .select(ParticipantRecord::as_select())
                .load::<ParticipantRecord>(self.connection)?;

            let mut model_conversation: Conversation = conversation.into();
            model_conversation.participants = db_participants.into_iter().map(|p| p.into()).collect();

            return Ok(Some(model_conversation));
        }

        Ok(None)
    }

    pub fn all_conversations(&mut self) -> Result<Vec<Conversation>> {
        use crate::schema::conversations::dsl::*;
        use crate::schema::participants::dsl::*;

        let db_conversations = conversations
            .load::<ConversationRecord>(self.connection)?;

        let mut result = Vec::new();
        for db_conversation in db_conversations {
            let db_participants = ConversationParticipant::belonging_to(&db_conversation)
                .inner_join(participants)
                .select(ParticipantRecord::as_select())
                .load::<ParticipantRecord>(self.connection)?;

            let mut model_conversation: Conversation = db_conversation.into();
            model_conversation.participants = db_participants.into_iter().map(|p| p.into()).collect();

            result.push(model_conversation);
        }

        Ok(result)
    }

    pub fn insert_message(&mut self, conversation_guid: &str, message: Message) -> Result<()> {
        use crate::schema::messages::dsl::*;
        use crate::schema::conversation_messages::dsl::*;

        // Handle participant if message has a remote sender
        let sender = message.sender.clone();
        let mut db_message: MessageRecord = message.into();
        db_message.sender_participant_id = self.get_or_create_participant(&sender);

        diesel::replace_into(messages)
            .values(&db_message)
            .execute(self.connection)?;

        diesel::replace_into(conversation_messages)
            .values((
                conversation_id.eq(conversation_guid),
                message_id.eq(&db_message.id),
            ))
            .execute(self.connection)?;

        Ok(())
    }

    pub fn insert_messages(&mut self, conversation_guid: &str, in_messages: Vec<Message>) -> Result<()> {
        use crate::schema::messages::dsl::*;
        use crate::schema::conversation_messages::dsl::*;

        // Local insertable struct for the join table
        #[derive(Insertable)]
        #[diesel(table_name = crate::schema::conversation_messages)]
        struct InsertableConversationMessage {
            pub conversation_id: String,
            pub message_id: String,
        }

        if in_messages.is_empty() {
            return Ok(());
        }

        // Build the collections of insertable records
        let mut db_messages: Vec<MessageRecord> = Vec::with_capacity(in_messages.len());
        let mut conv_msg_records: Vec<InsertableConversationMessage> = Vec::with_capacity(in_messages.len());

        for message in in_messages {
            // Handle participant if message has a remote sender
            let sender = message.sender.clone();
            let mut db_message: MessageRecord = message.into();
            db_message.sender_participant_id = self.get_or_create_participant(&sender);

            conv_msg_records.push(InsertableConversationMessage {
                conversation_id: conversation_guid.to_string(),
                message_id: db_message.id.clone(),
            });

            db_messages.push(db_message);
        }

        // Batch insert or replace messages
        diesel::replace_into(messages)
            .values(&db_messages)
            .execute(self.connection)?;

        // Batch insert the conversation-message links
        diesel::replace_into(conversation_messages)
            .values(&conv_msg_records)
            .execute(self.connection)?;

        Ok(())
    }

    pub fn get_messages_for_conversation(&mut self, conversation_guid: &str) -> Result<Vec<Message>> {
        use crate::schema::messages::dsl::*;
        use crate::schema::conversation_messages::dsl::*;
        use crate::schema::participants::dsl::*;

        let message_records = conversation_messages
            .filter(conversation_id.eq(conversation_guid))
            .inner_join(messages)
            .select(MessageRecord::as_select())
            .order_by(schema::messages::date.asc())
            .load::<MessageRecord>(self.connection)?;

        let mut result = Vec::new();
        for message_record in message_records {
            let mut message: Message = message_record.clone().into();
            
            // If there's a sender_participant_id, load the participant info
            if let Some(pid) = message_record.sender_participant_id {
                let participant = participants
                    .find(pid)
                    .first::<ParticipantRecord>(self.connection)?;
                message.sender = participant.into();
            }

            result.push(message);
        }

        Ok(result)
    }

    // Helper function to get the last inserted row ID
    // This is a workaround since the Sqlite backend doesn't support `RETURNING`
    // Huge caveat with this is that it depends on whatever the last insert was, prevents concurrent inserts.
    fn last_insert_id(&mut self) -> Result<i32> {
        Ok(diesel::select(diesel::dsl::sql::<diesel::sql_types::Integer>("last_insert_rowid()"))
            .get_result(self.connection)?)
    }

    fn get_or_create_participant(&mut self, participant: &Participant) -> Option<i32> {
        match participant {
            Participant::Me => None,
            Participant::Remote { display_name: p_name, .. } => {
                use crate::schema::participants::dsl::*;

                let existing_participant = participants
                    .filter(display_name.eq(p_name))
                    .first::<ParticipantRecord>(self.connection)
                    .optional()
                    .unwrap();

                if let Some(participant) = existing_participant {
                    return Some(participant.id);
                }

                let participant_record = InsertableParticipantRecord {
                    display_name: Some(participant.display_name()),
                    is_me: false,
                };

                diesel::insert_into(participants)
                    .values(&participant_record)
                    .execute(self.connection)
                    .unwrap();

                self.last_insert_id().ok()
            }
        }
    }
}