/*
 * meli - sqlite3.rs
 *
 * Copyright 2019 Manos Pitsidianakis
 *
 * This file is part of meli.
 *
 * meli is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * meli is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with meli. If not, see <http://www.gnu.org/licenses/>.
 */

/*! Use an sqlite3 database for fast searching.
 */
use smallvec::SmallVec;
use crate::cache::{escape_double_quote, query, Query::{self, *}};
use crate::melib::parsec::Parser;
use melib::{
    backends::MailBackend,
    email::{Envelope, EnvelopeHash},
    log,
    thread::{SortField, SortOrder},
    MeliError, Result, ERROR,
};
use rusqlite::{params, Connection};
use std::path::PathBuf;
use std::convert::TryInto;
use std::sync::{Arc, RwLock};

pub fn db_path() -> Result<PathBuf> {
    let data_dir =
        xdg::BaseDirectories::with_prefix("meli").map_err(|e| MeliError::new(e.to_string()))?;
    Ok(data_dir
        .place_data_file("index.db")
        .map_err(|e| MeliError::new(e.to_string()))?)
}

//#[inline(always)]
//fn fts5_bareword(w: &str) -> Cow<str> {
//    if w == "AND" || w == "OR" || w == "NOT" {
//        Cow::from(w)
//    } else {
//        if !w.is_ascii() {
//            Cow::from(format!("\"{}\"", escape_double_quote(w)))
//        } else {
//            for &b in w.as_bytes() {
//                if !(b > 0x2f && b < 0x3a)
//                    || !(b > 0x40 && b < 0x5b)
//                    || !(b > 0x60 && b < 0x7b)
//                    || b != 0x60
//                    || b != 26
//                {
//                    return Cow::from(format!("\"{}\"", escape_double_quote(w)));
//                }
//            }
//            Cow::from(w)
//        }
//    }
//}
//
pub fn open_db() -> Result<Connection> {
    let db_path = db_path()?;
    if !db_path.exists() {
        return Err(MeliError::new("Database hasn't been initialised. Run `reindex` command"));
    }
    Connection::open(&db_path).map_err(|e| MeliError::new(e.to_string()))
}

pub fn open_or_create_db() -> Result<Connection> {
    let db_path = db_path()?;
    let mut set_mode = false;
    if !db_path.exists() {
        log(
            format!("Creating index database in {}", db_path.display()),
            melib::INFO,
        );
        set_mode = true;
    }
    let conn = Connection::open(&db_path).map_err(|e| MeliError::new(e.to_string()))?;
    if set_mode {
        use std::os::unix::fs::PermissionsExt;
        let file = std::fs::File::open(&db_path)?;
        let metadata = file.metadata()?;
        let mut permissions = metadata.permissions();

        permissions.set_mode(0o600); // Read/write for owner only.
        file.set_permissions(permissions)?;
    }

    conn.execute_batch(
        "CREATE TABLE IF NOT EXISTS envelopes (
                    id               INTEGER PRIMARY KEY,
                    account_id       INTEGER REFERENCES accounts ON UPDATE CASCADE,
                    hash             BLOB NOT NULL UNIQUE,
                    date             TEXT NOT NULL,
                    _from            TEXT NOT NULL,
                    _to              TEXT NOT NULL,
                    cc               TEXT NOT NULL,
                    bcc              TEXT NOT NULL,
                    subject          TEXT NOT NULL,
                    message_id       TEXT NOT NULL,
                    in_reply_to      TEXT NOT NULL,
                    _references      TEXT NOT NULL,
                    flags            INTEGER NOT NULL,
                    has_attachments  BOOLEAN NOT NULL,
                    body_text        TEXT NOT NULL,
                    timestamp        BLOB NOT NULL
                   );
        CREATE TABLE IF NOT EXISTS folders (
                    id               INTEGER PRIMARY KEY,
                    account_id       INTEGER NOT NULL REFERENCES accounts ON UPDATE CASCADE,
                    hash             BLOB NOT NULL,
                    date             TEXT NOT NULL,
                    name             TEXT NOT NULL
                  );
        CREATE TABLE IF NOT EXISTS accounts (
                    id               INTEGER PRIMARY KEY,
                    name             TEXT NOT NULL UNIQUE
                  );
        CREATE TABLE IF NOT EXISTS folder_and_envelope (
                    folder_id        INTEGER NOT NULL,
                    envelope_id      INTEGER NOT NULL,
                    PRIMARY KEY (folder_id, envelope_id),
                    FOREIGN KEY(folder_id) REFERENCES folders(id) ON UPDATE CASCADE,
                    FOREIGN KEY(envelope_id) REFERENCES envelopes(id) ON UPDATE CASCADE
                  );
      CREATE INDEX IF NOT EXISTS folder_env_idx ON folder_and_envelope(folder_id);
      CREATE INDEX IF NOT EXISTS env_folder_idx ON folder_and_envelope(envelope_id);
      CREATE UNIQUE INDEX IF NOT EXISTS acc_idx ON accounts(name);


CREATE INDEX IF NOT EXISTS envelope_timestamp_index ON envelopes (timestamp);
CREATE INDEX IF NOT EXISTS envelope__from_index ON envelopes (_from);
CREATE INDEX IF NOT EXISTS envelope__to_index ON envelopes (_to);
CREATE INDEX IF NOT EXISTS envelope_cc_index ON envelopes (cc);
CREATE INDEX IF NOT EXISTS envelope_bcc_index ON envelopes (bcc);
CREATE INDEX IF NOT EXISTS envelope_message_id_index ON envelopes (message_id);

        CREATE VIRTUAL TABLE IF NOT EXISTS fts USING fts5(subject, body_text, content=envelopes, content_rowid=id);

-- Triggers to keep the FTS index up to date.
CREATE TRIGGER IF NOT EXISTS envelopes_ai AFTER INSERT ON envelopes BEGIN
  INSERT INTO fts(rowid, subject, body_text) VALUES (new.id, new.subject, new.body_text);
END;

CREATE TRIGGER IF NOT EXISTS envelopes_ad AFTER DELETE ON envelopes BEGIN
  INSERT INTO fts(fts, rowid, subject, body_text) VALUES('delete', old.id, old.subject, old.body_text);
END;

CREATE TRIGGER IF NOT EXISTS envelopes_au AFTER UPDATE ON envelopes BEGIN
  INSERT INTO fts(fts, rowid, subject, body_text) VALUES('delete', old.id, old.subject, old.body_text);
  INSERT INTO fts(rowid, subject, body_text) VALUES (new.id, new.subject, new.body_text);
END; ",
    )
    .map_err(|e| MeliError::new(e.to_string()))?;

    Ok(conn)
}

pub fn insert(envelope: &Envelope, backend: &Arc<RwLock<Box<dyn MailBackend>>>, acc_name: &str) -> Result<()> {
    let conn = open_db()?;
    let backend_lck = backend.read().unwrap();
    let op = backend_lck.operation(envelope.hash());
    let body = match envelope.body(op) {
        Ok(body) => body.text(),
        Err(err) => {
            debug!(
                "{}",
                format!(
                    "Failed to open envelope {}: {}",
                    envelope.message_id_display(),
                    err.to_string()
                )
            );
            log(
                format!(
                    "Failed to open envelope {}: {}",
                    envelope.message_id_display(),
                    err.to_string()
                ),
                ERROR,
            );
            return Err(err);
        }
    };

    if let Err(err) = conn.execute("INSERT OR IGNORE INTO accounts (name) VALUES (?1)", params![acc_name, ]) {
        debug!(
            "Failed to insert envelope {}: {}",
            envelope.message_id_display(),
            err.to_string()
        );
        log(
            format!(
                "Failed to insert envelope {}: {}",
                envelope.message_id_display(),
                err.to_string()
            ),
            ERROR,
        );
        return Err(MeliError::new(err.to_string()));
    }
    let account_id: i32 = {
        let mut stmt = conn.prepare("SELECT id FROM accounts WHERE name = ?").unwrap();
        let x = stmt.query_map(params![acc_name], |row| row.get(0)).unwrap().next().unwrap().unwrap();
        x
    };
    if let Err(err) = conn.execute(
            "INSERT OR REPLACE INTO envelopes (account_id, hash, date, _from, _to, cc, bcc, subject, message_id, in_reply_to, _references, flags, has_attachments, body_text, timestamp)
              VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9, ?10, ?11, ?12, ?13, ?14, ?15)",
              params![account_id, envelope.hash().to_be_bytes().to_vec(), envelope.date_as_str(), envelope.field_from_to_string(), envelope.field_to_to_string(), envelope.field_cc_to_string(), envelope.field_bcc_to_string(), envelope.subject().into_owned().trim_end_matches('\u{0}'), envelope.message_id_display().to_string(), envelope.in_reply_to_display().map(|f| f.to_string()).unwrap_or(String::new()), envelope.field_references_to_string(), i64::from(envelope.flags().bits()), if envelope.has_attachments() { 1 } else { 0 }, body, envelope.date().to_be_bytes().to_vec()],
        )
            .map_err(|e| MeliError::new(e.to_string())) {
                debug!(
                        "Failed to insert envelope {}: {}",
                        envelope.message_id_display(),
                        err.to_string()
                    );
                log(
                    format!(
                        "Failed to insert envelope {}: {}",
                        envelope.message_id_display(),
                        err.to_string()
                    ),
                    ERROR,
                );
              }
    Ok(())
}

pub fn remove(env_hash: EnvelopeHash) -> Result<()> {
    let conn = open_db()?;
    if let Err(err) = conn.execute(
        "DELETE FROM envelopes WHERE hash = ?",
        params![env_hash.to_be_bytes().to_vec(), ])
        .map_err(|e| MeliError::new(e.to_string())) {
            debug!(
                "Failed to remove envelope {}: {}",
                env_hash,
                err.to_string()
            );
            log(
                format!(
                    "Failed to remove envelope {}: {}",
                    env_hash,
                    err.to_string()
                ),
                ERROR,
            );
            return Err(err);
    }
    Ok(())
}

pub fn index(context: &mut crate::state::Context, account_name: &str) -> Result<()> {
    let account = if let Some(a) =  context.accounts.iter().find(|acc| acc.name() == account_name) {
        a} else {
            return Err(MeliError::new(format!("Account {} was not found.", account_name)));
    };

    let (acc_name, acc_mutex, backend_mutex):( String, Arc<RwLock<_>>, Arc<_>) = if *account.settings.conf.cache_type() != crate::conf::CacheType::Sqlite3 {
            return Err(MeliError::new(format!("Account {} doesn't have an sqlite3 search backend.", account_name)));
    } else {
            (
                account.name().to_string(),
                account.collection.envelopes.clone(),
                account.backend.clone(),
            )};
    let conn = open_or_create_db()?;
    let work_context = context.work_controller().get_context();
    let env_hashes =
        acc_mutex.read().unwrap().keys().cloned().collect::<Vec<_>>();

    /* Sleep, index and repeat in order not to block the main process */
    let handle = std::thread::Builder::new().name(String::from("rebuilding index")).spawn(move || {
        let thread_id = std::thread::current().id();

        let sleep_dur = std::time::Duration::from_millis(20);
            if let Err(err) = conn.execute(
                "INSERT OR REPLACE INTO accounts (name) VALUES (?1)", params![acc_name.as_str(),],).map_err(|e| MeliError::new(e.to_string())) {
                debug!("{}",
                    format!(
                        "Failed to update index: {}",
                        err.to_string()
                    ));
                log(
                    format!(
                        "Failed to update index: {}",
                        err.to_string()
                    ),
                    ERROR,
                );
            } 
            let account_id: i32 = {
                let mut stmt = conn.prepare("SELECT id FROM accounts WHERE name = ?").unwrap();
                let x = stmt.query_map(params![acc_name.as_str()], |row| row.get(0)).unwrap().next().unwrap().unwrap();
                x
            };
            let mut ctr = 0;
            debug!("{}", format!("Rebuilding {} index. {}/{}", acc_name, ctr, env_hashes.len()));
            work_context
                .set_status
                .send((thread_id, format!("Rebuilding {} index. {}/{}", acc_name, ctr, env_hashes.len())))
                .unwrap();
            for chunk in env_hashes.chunks(200) {
                ctr += chunk.len();
                let envelopes_lck = acc_mutex.read().unwrap();
                let backend_lck = backend_mutex.read().unwrap();
                for env_hash in chunk {
                    if let Some(e) = envelopes_lck.get(&env_hash) {
                        let op = backend_lck.operation(e.hash());
                        let body = match e.body(op) {
                            Ok(body) => body.text(),
                            Err(err) => {
                                debug!("{}",
                                    format!(
                                        "Failed to open envelope {}: {}",
                                        e.message_id_display(),
                                        err.to_string()
                                    ));
                                log(
                                    format!(
                                        "Failed to open envelope {}: {}",
                                        e.message_id_display(),
                                        err.to_string()
                                    ),
                                    ERROR,
                                );
                                return;
                            }
                        };
                        if let Err(err) = conn.execute(
                            "INSERT OR REPLACE INTO envelopes (account_id, hash, date, _from, _to, cc, bcc, subject, message_id, in_reply_to, _references, flags, has_attachments, body_text, timestamp)
              VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9, ?10, ?11, ?12, ?13, ?14, ?15)",
              params![account_id, e.hash().to_be_bytes().to_vec(), e.date_as_str(), e.field_from_to_string(), e.field_to_to_string(), e.field_cc_to_string(), e.field_bcc_to_string(), e.subject().into_owned().trim_end_matches('\u{0}'), e.message_id_display().to_string(), e.in_reply_to_display().map(|f| f.to_string()).unwrap_or(String::new()), e.field_references_to_string(), i64::from(e.flags().bits()), if e.has_attachments() { 1 } else { 0 }, body, e.date().to_be_bytes().to_vec()],
                        )
                            .map_err(|e| MeliError::new(e.to_string())) {
                                debug!("{}",
                                    format!(
                                        "Failed to insert envelope {}: {}",
                                        e.message_id_display(),
                                        err.to_string()
                                    ));
                                log(
                                    format!(
                                        "Failed to insert envelope {}: {}",
                                        e.message_id_display(),
                                        err.to_string()
                                    ),
                                    ERROR,
                                );
              }
                    }
                }
                drop(envelopes_lck);
                work_context
                    .set_status
                    .send((thread_id, format!("Rebuilding {} index. {}/{}", acc_name, ctr, env_hashes.len())))
                    .unwrap();
                std::thread::sleep(sleep_dur);
        }
        work_context.finished.send(thread_id).unwrap();
    })?;
    context.work_controller().static_threads.lock()?.insert(
        handle.thread().id(),
        String::from("Rebuilding sqlite3 index").into(),
    );

    Ok(())
}

pub fn search(
    term: &str,
    (sort_field, sort_order): (SortField, SortOrder),
) -> Result<SmallVec<[EnvelopeHash; 512]>> {
    let conn = open_db()?;

    let sort_field = match debug!(sort_field) {
        SortField::Subject => "subject",
        SortField::Date => "timestamp",
    };

    let sort_order = match debug!(sort_order) {
        SortOrder::Asc => "ASC",
        SortOrder::Desc => "DESC",
    };

    let mut stmt = conn
        .prepare(
            debug!(format!(
                "SELECT hash FROM envelopes WHERE {} ORDER BY {} {};",
                query_to_sql(&query().parse(term)?.1),
                sort_field,
                sort_order
            ))
            .as_str(),
        )
        .map_err(|e| MeliError::new(e.to_string()))?;

    let results = stmt
        .query_map(rusqlite::NO_PARAMS, |row| Ok(row.get(0)?))
        .map_err(|e| MeliError::new(e.to_string()))?
        .map(|r: std::result::Result<Vec<u8>, rusqlite::Error>| {
            Ok(u64::from_be_bytes(
                r.map_err(|e| MeliError::new(e.to_string()))?
                    .as_slice()
                    .try_into()
                    .map_err(|e: std::array::TryFromSliceError| MeliError::new(e.to_string()))?,
            ))
        })
        .collect::<Result<SmallVec<[EnvelopeHash; 512]>>>();
    results
}

/// Translates a `Query` to an Sqlite3 expression in a `String`.
pub fn query_to_sql(q: &Query) -> String {
    fn rec(q: &Query, s: &mut String) {
        match q {
            Subject(t) => {
                s.push_str("subject LIKE \"%");
                s.extend(escape_double_quote(t).chars());
                s.push_str("%\" ");
            }
            From(t) => {
                s.push_str("_from LIKE \"%");
                s.extend(escape_double_quote(t).chars());
                s.push_str("%\" ");
            }
            To(t) => {
                s.push_str("_to LIKE \"%");
                s.extend(escape_double_quote(t).chars());
                s.push_str("%\" ");
            }
            Cc(t) => {
                s.push_str("cc LIKE \"%");
                s.extend(escape_double_quote(t).chars());
                s.push_str("%\" ");
            }
            Bcc(t) => {
                s.push_str("bcc LIKE \"%");
                s.extend(escape_double_quote(t).chars());
                s.push_str("%\" ");
            }
            AllText(t) => {
                s.push_str("body_text LIKE \"%");
                s.extend(escape_double_quote(t).chars());
                s.push_str("%\" ");
            }
            And(q1, q2) => {
                s.push_str("(");
                rec(q1, s);
                s.push_str(") AND (");
                rec(q2, s);
                s.push_str(") ");
            }
            Or(q1, q2) => {
                s.push_str("(");
                rec(q1, s);
                s.push_str(") OR (");
                rec(q2, s);
                s.push_str(") ");
            }
            Not(q) => {
                s.push_str("NOT (");
                rec(q, s);
                s.push_str(") ");
            }
            Flags(v) => {
                let total = v.len();
                if total > 1 {
                    s.push_str("(");
                }
                for (i, f) in v.iter().enumerate() {
                    match f.as_str() {
                        "draft" => {
                            s.push_str(" (flags & 8 > 0) ");
                        }
                        "deleted" | "trashed" => {
                            s.push_str(" (flags & 6 > 0) ");
                        }
                        "flagged" => {
                            s.push_str(" (flags & 16 > 0) ");
                        }
                        "recent" => {
                            s.push_str(" (flags & 4 == 0) ");
                        }
                        "seen" | "read" => {
                            s.push_str(" (flags & 4 > 0) ");
                        }
                        "unseen" | "unread" => {
                            s.push_str(" (flags & 4 == 0) ");
                        }
                        "answered" | "replied" => {
                            s.push_str(" (flags & 2 > 0) ");
                        }
                        "unanswered" => {
                            s.push_str(" (flags & 2 == 0) ");
                        }
                        _ => {
                            continue;
                        }
                    }
                    if total > 1 && i != total - 1 {
                        s.push_str(" AND ");
                    }
                }
                if total > 1 {
                    s.push_str(") ");
                }
            }
            HasAttachment => {
                s.push_str("has_attachments == 1 ");
            }
            _ => {}
        }
    }
    let mut ret = String::new();
    rec(q, &mut ret);
    ret
}

#[test]
fn test_query_to_sql() {
    assert_eq!(
        "(subject LIKE \"%test%\" ) AND (body_text LIKE \"%i%\" ) ",
        &query_to_sql(&query().parse_complete("subject: test and i").unwrap().1)
    );
    assert_eq!(
        "(subject LIKE \"%github%\" ) OR ((_from LIKE \"%epilys%\" ) AND ((subject LIKE \"%lib%\" ) OR (subject LIKE \"%meli%\" ) ) ) ",
        &query_to_sql(
            &query()
                .parse_complete(
                    "subject: github or (from: epilys and (subject:lib or subject: meli))"
                )
                .unwrap()
                .1
        )
    );
}