use instance::Instance;
use posts::Post;
use tags::Tag;
use Connection;

use chrono::Datelike;
use itertools::Itertools;
use tantivy::{
    collector::TopDocs, directory::MmapDirectory,
    schema::*, tokenizer::*, Index, IndexWriter, Term
};
use whatlang::{detect as detect_lang, Lang};
use std::{cmp, fs::create_dir_all, path::Path, sync::Mutex};

use search::query::PlumeQuery;
use super::tokenizer;
use Result;

#[derive(Debug)]
pub enum SearcherError {
    IndexCreationError,
    WriteLockAcquisitionError,
    IndexOpeningError,
    IndexEditionError,
}

pub struct Searcher {
    index: Index,
    writer: Mutex<Option<IndexWriter>>,
}

impl Searcher {
    pub fn schema() -> Schema {
        let tag_indexing = TextOptions::default()
            .set_indexing_options(TextFieldIndexing::default()
                                  .set_tokenizer("whitespace_tokenizer")
                                  .set_index_option(IndexRecordOption::Basic));

        let content_indexing = TextOptions::default()
            .set_indexing_options(TextFieldIndexing::default()
                                  .set_tokenizer("content_tokenizer")
                                  .set_index_option(IndexRecordOption::WithFreqsAndPositions));

        let property_indexing = TextOptions::default()
            .set_indexing_options(TextFieldIndexing::default()
                                  .set_tokenizer("property_tokenizer")
                                  .set_index_option(IndexRecordOption::WithFreqsAndPositions));

        let mut schema_builder = SchemaBuilder::default();

        schema_builder.add_i64_field("post_id", INT_STORED | INT_INDEXED);
        schema_builder.add_i64_field("creation_date", INT_INDEXED);

        schema_builder.add_text_field("instance", tag_indexing.clone());
        schema_builder.add_text_field("author", tag_indexing.clone());
        schema_builder.add_text_field("tag", tag_indexing);

        schema_builder.add_text_field("blog", content_indexing.clone());
        schema_builder.add_text_field("content", content_indexing.clone());
        schema_builder.add_text_field("subtitle", content_indexing.clone());
        schema_builder.add_text_field("title", content_indexing);

        schema_builder.add_text_field("lang", property_indexing.clone());
        schema_builder.add_text_field("license", property_indexing);

        schema_builder.build()
    }


    pub fn create(path: &AsRef<Path>) -> Result<Self> {
        let whitespace_tokenizer = tokenizer::WhitespaceTokenizer
            .filter(LowerCaser);

        let content_tokenizer = SimpleTokenizer
            .filter(RemoveLongFilter::limit(40))
            .filter(LowerCaser);

        let property_tokenizer = NgramTokenizer::new(2, 8, false)
            .filter(LowerCaser);

        let schema = Self::schema();

        create_dir_all(path).map_err(|_| SearcherError::IndexCreationError)?;
        let index = Index::create(MmapDirectory::open(path).map_err(|_| SearcherError::IndexCreationError)?, schema).map_err(|_| SearcherError::IndexCreationError)?;

        {
            let tokenizer_manager = index.tokenizers();
            tokenizer_manager.register("whitespace_tokenizer", whitespace_tokenizer);
            tokenizer_manager.register("content_tokenizer", content_tokenizer);
            tokenizer_manager.register("property_tokenizer", property_tokenizer);
        }//to please the borrow checker
        Ok(Self {
            writer: Mutex::new(Some(index.writer(50_000_000).map_err(|_| SearcherError::WriteLockAcquisitionError)?)),
            index
        })
    }

    pub fn open(path: &AsRef<Path>) -> Result<Self> {
        let whitespace_tokenizer = tokenizer::WhitespaceTokenizer
            .filter(LowerCaser);

        let content_tokenizer = SimpleTokenizer
            .filter(RemoveLongFilter::limit(40))
            .filter(LowerCaser);

        let property_tokenizer = NgramTokenizer::new(2, 8, false)
            .filter(LowerCaser);

        let index = Index::open(MmapDirectory::open(path).map_err(|_| SearcherError::IndexOpeningError)?).map_err(|_| SearcherError::IndexOpeningError)?;

        {
            let tokenizer_manager = index.tokenizers();
            tokenizer_manager.register("whitespace_tokenizer", whitespace_tokenizer);
            tokenizer_manager.register("content_tokenizer", content_tokenizer);
            tokenizer_manager.register("property_tokenizer", property_tokenizer);
        }//to please the borrow checker
        let mut writer = index.writer(50_000_000).map_err(|_| SearcherError::WriteLockAcquisitionError)?;
        writer.garbage_collect_files().map_err(|_| SearcherError::IndexEditionError)?;
        Ok(Self {
            writer: Mutex::new(Some(writer)),
            index,
        })
    }

    pub fn add_document(&self, conn: &Connection, post: &Post) -> Result<()> {
        let schema = self.index.schema();

        let post_id = schema.get_field("post_id").unwrap();
        let creation_date = schema.get_field("creation_date").unwrap();

        let instance = schema.get_field("instance").unwrap();
        let author = schema.get_field("author").unwrap();
        let tag = schema.get_field("tag").unwrap();

        let blog_name = schema.get_field("blog").unwrap();
        let content = schema.get_field("content").unwrap();
        let subtitle = schema.get_field("subtitle").unwrap();
        let title = schema.get_field("title").unwrap();

        let lang = schema.get_field("lang").unwrap();
        let license = schema.get_field("license").unwrap();

        let mut writer = self.writer.lock().unwrap();
        let writer = writer.as_mut().unwrap();
        writer.add_document(doc!(
            post_id => i64::from(post.id),
            author => post.get_authors(conn)?.into_iter().map(|u| u.fqn).join(" "),
            creation_date => i64::from(post.creation_date.num_days_from_ce()),
            instance => Instance::get(conn, post.get_blog(conn)?.instance_id)?.public_domain.clone(),
            tag => Tag::for_post(conn, post.id)?.into_iter().map(|t| t.tag).join(" "),
            blog_name => post.get_blog(conn)?.title,
            content => post.content.get().clone(),
            subtitle => post.subtitle.clone(),
            title => post.title.clone(),
            lang => detect_lang(post.content.get()).and_then(|i| if i.is_reliable() { Some(i.lang()) } else {None} ).unwrap_or(Lang::Eng).name(),
            license => post.license.clone(),
        ));
        Ok(())
    }

    pub fn delete_document(&self, post: &Post) {
        let schema = self.index.schema();
        let post_id = schema.get_field("post_id").unwrap();

        let doc_id = Term::from_field_i64(post_id, i64::from(post.id));
        let mut writer = self.writer.lock().unwrap();
        let writer = writer.as_mut().unwrap();
        writer.delete_term(doc_id);
    }

    pub fn update_document(&self, conn: &Connection, post: &Post) -> Result<()> {
        self.delete_document(post);
        self.add_document(conn, post)
    }

    pub fn search_document(&self, conn: &Connection, query: PlumeQuery, (min, max): (i32, i32)) -> Vec<Post>{
        let schema = self.index.schema();
        let post_id = schema.get_field("post_id").unwrap();

        let collector = TopDocs::with_limit(cmp::max(1,max) as usize);

        let searcher = self.index.searcher();
        let res = searcher.search(&query.into_query(), &collector).unwrap();

        res.get(min as usize..).unwrap_or(&[])
            .iter()
            .filter_map(|(_,doc_add)| {
                let doc = searcher.doc(*doc_add).ok()?;
                let id = doc.get_first(post_id)?;
                Post::get(conn, id.i64_value() as i32).ok()
                //borrow checker don't want me to use filter_map or and_then here
            })
            .collect()
    }

    pub fn commit(&self) {
        let mut writer = self.writer.lock().unwrap();
        writer.as_mut().unwrap().commit().unwrap();
        self.index.load_searchers().unwrap();
    }

    pub fn drop_writer(&self) {
        self.writer.lock().unwrap().take();
    }
}