use clap::ArgMatches;
use serde_json;
use std::str::FromStr;
use std::convert::From;
use std::path::Path;
use std::path::PathBuf;
use tantivy;
use tantivy::query::QueryParser;
use tantivy::schema::Field;
use tantivy::schema::FieldType;
use tantivy::Index;
use tantivy::collector::{Count, TopDocs};
use tantivy::Document;

pub fn run_search_cli(matches: &ArgMatches) -> Result<(), String> {
    let index_directory = PathBuf::from(matches.value_of("index").unwrap());
    let query = matches.value_of("query").unwrap();
    match matches.value_of("num_hits") {
        Some(num_hits_str) => {
            let num_hits: usize = FromStr::from_str(num_hits_str)
                .map_err(|e| { format!("Failed to parse --num_hits (got '{}', expected integer): {}", num_hits_str, e) })?;
            run_top_search(&index_directory, &query, num_hits)
                .map_err(|e| format!("{:?}", e))
        }

        None => {
            run_search(&index_directory, &query).map_err(|e| format!("{:?}", e))
        }
    }
}

fn run_search(directory: &Path, query: &str) -> tantivy::Result<()> {
    let index = Index::open_in_dir(directory)?;
    let schema = index.schema();
    let default_fields: Vec<Field> = schema
        .fields()
        .filter(|&(_, ref field_entry)| match *field_entry.field_type() {
            FieldType::Str(ref text_field_options) => {
                text_field_options.get_indexing_options().is_some()
            }
            _ => false,
        })
        .map(|(field, _)| field)
        .collect();
    let query_parser = QueryParser::new(schema.clone(), default_fields, index.tokenizers().clone());
    let query = query_parser.parse_query(query)?;
    let searcher = index.reader()?.searcher();
    let weight = query.weight(&searcher, false)?;
    let schema = index.schema();
    for segment_reader in searcher.segment_readers() {
        let mut scorer = weight.scorer(segment_reader, 1.0)?;
        let store_reader = segment_reader.get_store_reader();
        while scorer.advance() {
            let doc_id = scorer.doc();
            let doc = store_reader.get(doc_id)?;
            let named_doc = schema.to_named_doc(&doc);
            println!("{}", serde_json::to_string(&named_doc).unwrap());
        }
    }
    Ok(())
}

fn run_top_search(directory: &Path, query: &str, num_hits: usize) -> tantivy::Result<()> {
    let index = Index::open_in_dir(directory)?;
    let schema = index.schema();
    let default_fields: Vec<Field> = schema
        .fields()
        .filter(|(_, field_entry)| {
            match field_entry.field_type() {
                FieldType::Str(ref text_field_options) => {
                    text_field_options.get_indexing_options().is_some()
                }
                _ => false,
            }
        })
        .map(|(field, _)| field)
        .collect();
    let query_parser = QueryParser::new(schema.clone(), default_fields, index.tokenizers().clone());
    let query = query_parser.parse_query(query)?;
    let searcher = index.reader()?.searcher();
    let (top_docs, num_hits) = searcher.search(&query, &(TopDocs::with_limit(num_hits), Count))?;
    let mut out = String::with_capacity(1024);
    top_docs
        .iter()
        .take(num_hits)
        .for_each(|(_score, doc_address)| {
            let doc: Document = searcher.doc(*doc_address).unwrap();
            let named_doc = schema.to_named_doc(&doc); 
            let json_doc: String = serde_json::to_string(&named_doc).unwrap();
            out.push_str(&format!("{}\n", json_doc));
        });
    print!("{}", out);
    Ok(())
}