use std::collections::HashMap;
use std::ops::Deref;
use std::sync::Arc;

use chrono::{DateTime, Utc};
use heed::types::{SerdeBincode, Str};
use log::error;
use meilisearch_core::{Database, DatabaseOptions, Error as MError, MResult, MainT, UpdateT};
use sha2::Digest;
use sysinfo::Pid;

use crate::index_update_callback;
use crate::option::Opt;

const LAST_UPDATE_KEY: &str = "last-update";

type SerdeDatetime = SerdeBincode<DateTime<Utc>>;

#[derive(Clone)]
pub struct Data {
    inner: Arc<DataInner>,
}

impl Deref for Data {
    type Target = DataInner;

    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

#[derive(Clone)]
pub struct DataInner {
    pub db: Arc<Database>,
    pub db_path: String,
    pub api_keys: ApiKeys,
    pub server_pid: Pid,
}

#[derive(Clone)]
pub struct ApiKeys {
    pub public: Option<String>,
    pub private: Option<String>,
    pub master: Option<String>,
}

impl ApiKeys {
    pub fn generate_missing_api_keys(&mut self) {
        if let Some(master_key) = &self.master {
            if self.private.is_none() {
                let key = format!("{}-private", master_key);
                let sha = sha2::Sha256::digest(key.as_bytes());
                self.private = Some(format!("{:x}", sha));
            }
            if self.public.is_none() {
                let key = format!("{}-public", master_key);
                let sha = sha2::Sha256::digest(key.as_bytes());
                self.public = Some(format!("{:x}", sha));
            }
        }
    }
}

impl DataInner {
    pub fn is_indexing(&self, reader: &heed::RoTxn<UpdateT>, index: &str) -> MResult<Option<bool>> {
        match self.db.open_index(&index) {
            Some(index) => index.current_update_id(&reader).map(|u| Some(u.is_some())),
            None => Ok(None),
        }
    }

    pub fn last_update(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<DateTime<Utc>>> {
        match self
            .db
            .common_store()
            .get::<_, Str, SerdeDatetime>(reader, LAST_UPDATE_KEY)?
        {
            Some(datetime) => Ok(Some(datetime)),
            None => Ok(None),
        }
    }

    pub fn set_last_update(&self, writer: &mut heed::RwTxn<MainT>) -> MResult<()> {
        self.db
            .common_store()
            .put::<_, Str, SerdeDatetime>(writer, LAST_UPDATE_KEY, &Utc::now())
            .map_err(Into::into)
    }

    pub fn compute_stats(&self, writer: &mut heed::RwTxn<MainT>, index_uid: &str) -> MResult<()> {
        let index = match self.db.open_index(&index_uid) {
            Some(index) => index,
            None => {
                error!("Impossible to retrieve index {}", index_uid);
                return Ok(());
            }
        };

        let schema = match index.main.schema(&writer)? {
            Some(schema) => schema,
            None => return Ok(()),
        };

        let all_documents_fields = index
            .documents_fields_counts
            .all_documents_fields_counts(&writer)?;

        // count fields frequencies
        let mut fields_frequency = HashMap::<_, usize>::new();
        for result in all_documents_fields {
            let (_, attr, _) = result?;
            if let Some(field_id) = schema.indexed_pos_to_field_id(attr) {
                *fields_frequency.entry(field_id).or_default() += 1;
            }
        }

        // convert attributes to their names
        let frequency: HashMap<_, _> = fields_frequency
            .into_iter()
            .filter_map(|(a, c)| schema.name(a).map(|name| (name.to_string(), c)))
            .collect();

        index
            .main
            .put_fields_frequency(writer, &frequency)
            .map_err(MError::Zlmdb)
    }
}

impl Data {
    pub fn new(opt: Opt) -> Data {
        let db_path = opt.db_path.clone();
        let server_pid = sysinfo::get_current_pid().unwrap();

        let db_opt = DatabaseOptions {
            main_map_size: opt.main_map_size,
            update_map_size: opt.update_map_size
        };

        let db = Arc::new(Database::open_or_create(opt.db_path, db_opt).unwrap());

        let mut api_keys = ApiKeys {
            master: opt.master_key,
            private: None,
            public: None,
        };

        api_keys.generate_missing_api_keys();

        let inner_data = DataInner {
            db: db.clone(),
            db_path,
            api_keys,
            server_pid,
        };

        let data = Data {
            inner: Arc::new(inner_data),
        };

        let callback_context = data.clone();
        db.set_update_callback(Box::new(move |index_uid, status| {
            index_update_callback(&index_uid, &callback_context, status);
        }));

        data
    }
}