use std::cmp::Reverse;
use std::collections::HashSet;
use std::io::Cursor;
use std::time::Duration;

use big_s::S;
use either::{Either, Left, Right};
use heed::EnvOpenOptions;
use maplit::{btreemap, hashset};
use meili_snap::snapshot;
use milli::documents::{DocumentsBatchBuilder, DocumentsBatchReader};
use milli::update::{IndexDocuments, IndexDocumentsConfig, IndexerConfig, Settings};
use milli::{
    AscDesc, Criterion, DocumentId, Filter, Index, Member, Object, Search, TermsMatchingStrategy,
    TimeBudget,
};
use serde::{Deserialize, Deserializer};
use slice_group_by::GroupBy;

mod distinct;
mod facet_distribution;
mod filters;
mod phrase_search;
mod query_criteria;
mod sort;
mod typo_tolerance;

pub const TEST_QUERY: &str = "hello world america";

pub const EXTERNAL_DOCUMENTS_IDS: &[&str; 17] =
    &["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q"];

pub const CONTENT: &str = include_str!("../assets/test_set.ndjson");

pub fn setup_search_index_with_criteria(criteria: &[Criterion]) -> Index {
    let path = tempfile::tempdir().unwrap();
    let mut options = EnvOpenOptions::new();
    options.map_size(10 * 1024 * 1024); // 10 MB
    let index = Index::new(options, &path).unwrap();

    let mut wtxn = index.write_txn().unwrap();
    let config = IndexerConfig::default();

    let mut builder = Settings::new(&mut wtxn, &index, &config);

    builder.set_criteria(criteria.to_vec());
    builder.set_filterable_fields(hashset! {
        S("tag"),
        S("asc_desc_rank"),
        S("_geo"),
        S("opt1"),
        S("opt1.opt2"),
        S("tag_in")
    });
    builder.set_sortable_fields(hashset! {
        S("tag"),
        S("asc_desc_rank"),
    });
    builder.set_synonyms(btreemap! {
        S("hello") => vec![S("good morning")],
        S("world") => vec![S("earth")],
        S("america") => vec![S("the united states")],
    });
    builder.set_searchable_fields(vec![S("title"), S("description")]);
    builder.execute(|_| (), || false).unwrap();

    // index documents
    let config = IndexerConfig { max_memory: Some(10 * 1024 * 1024), ..Default::default() };
    let indexing_config = IndexDocumentsConfig::default();

    let builder =
        IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| (), || false).unwrap();
    let mut documents_builder = DocumentsBatchBuilder::new(Vec::new());
    let reader = Cursor::new(CONTENT.as_bytes());

    for result in serde_json::Deserializer::from_reader(reader).into_iter::<Object>() {
        let object = result.unwrap();
        documents_builder.append_json_object(&object).unwrap();
    }

    let vector = documents_builder.into_inner().unwrap();

    // index documents
    let content = DocumentsBatchReader::from_reader(Cursor::new(vector)).unwrap();
    let (builder, user_error) = builder.add_documents(content).unwrap();
    user_error.unwrap();
    builder.execute().unwrap();

    wtxn.commit().unwrap();

    index
}

pub fn internal_to_external_ids(index: &Index, internal_ids: &[DocumentId]) -> Vec<String> {
    let rtxn = index.read_txn().unwrap();
    let docid_map = index.external_documents_ids();
    let docid_map: std::collections::HashMap<_, _> = EXTERNAL_DOCUMENTS_IDS
        .iter()
        .map(|id| (docid_map.get(&rtxn, id).unwrap().unwrap(), id))
        .collect();
    internal_ids.iter().map(|id| docid_map.get(id).unwrap().to_string()).collect()
}

pub fn expected_order(
    criteria: &[Criterion],
    optional_words: TermsMatchingStrategy,
    sort_by: &[AscDesc],
) -> Vec<TestDocument> {
    let dataset =
        serde_json::Deserializer::from_str(CONTENT).into_iter().map(|r| r.unwrap()).collect();
    let mut groups: Vec<Vec<TestDocument>> = vec![dataset];

    for criterion in criteria {
        let mut new_groups = Vec::new();
        for group in groups.iter_mut() {
            match criterion {
                Criterion::Attribute => {
                    group.sort_by_key(|d| d.attribute_rank);
                    new_groups
                        .extend(group.linear_group_by_key(|d| d.attribute_rank).map(Vec::from));
                }
                Criterion::Exactness => {
                    group.sort_by_key(|d| d.exact_rank);
                    new_groups.extend(group.linear_group_by_key(|d| d.exact_rank).map(Vec::from));
                }
                Criterion::Proximity => {
                    group.sort_by_key(|d| d.proximity_rank);
                    new_groups
                        .extend(group.linear_group_by_key(|d| d.proximity_rank).map(Vec::from));
                }
                Criterion::Sort if sort_by == [AscDesc::Asc(Member::Field(S("tag")))] => {
                    group.sort_by_key(|d| d.sort_by_rank);
                    new_groups.extend(group.linear_group_by_key(|d| d.sort_by_rank).map(Vec::from));
                }
                Criterion::Sort if sort_by == [AscDesc::Desc(Member::Field(S("tag")))] => {
                    group.sort_by_key(|d| Reverse(d.sort_by_rank));
                    new_groups.extend(group.linear_group_by_key(|d| d.sort_by_rank).map(Vec::from));
                }
                Criterion::Typo => {
                    group.sort_by_key(|d| d.typo_rank);
                    new_groups.extend(group.linear_group_by_key(|d| d.typo_rank).map(Vec::from));
                }
                Criterion::Words => {
                    group.sort_by_key(|d| d.word_rank);
                    new_groups.extend(group.linear_group_by_key(|d| d.word_rank).map(Vec::from));
                }
                Criterion::Asc(field_name) if field_name == "asc_desc_rank" => {
                    group.sort_by_key(|d| d.asc_desc_rank);
                    new_groups
                        .extend(group.linear_group_by_key(|d| d.asc_desc_rank).map(Vec::from));
                }
                Criterion::Desc(field_name) if field_name == "asc_desc_rank" => {
                    group.sort_by_key(|d| Reverse(d.asc_desc_rank));
                    new_groups
                        .extend(group.linear_group_by_key(|d| d.asc_desc_rank).map(Vec::from));
                }
                Criterion::Asc(_) | Criterion::Desc(_) | Criterion::Sort => {
                    new_groups.push(group.clone())
                }
            }
        }
        groups = std::mem::take(&mut new_groups);
    }

    match optional_words {
        TermsMatchingStrategy::Last => groups.into_iter().flatten().collect(),
        TermsMatchingStrategy::All => {
            groups.into_iter().flatten().filter(|d| d.word_rank == 0).collect()
        }
    }
}

fn execute_filter(filter: &str, document: &TestDocument) -> Option<String> {
    let mut id = None;
    if let Some((field, filter)) = filter.split_once("!=") {
        if field == "tag" && document.tag != filter
            || (field == "asc_desc_rank"
                && Ok(&document.asc_desc_rank) != filter.parse::<u32>().as_ref())
        {
            id = Some(document.id.clone())
        }
    } else if let Some((field, filter)) = filter.split_once('=') {
        if field == "tag" && document.tag == filter
            || (field == "asc_desc_rank"
                && document.asc_desc_rank == filter.parse::<u32>().unwrap())
        {
            id = Some(document.id.clone())
        }
    } else if let Some(("asc_desc_rank", filter)) = filter.split_once('<') {
        if document.asc_desc_rank < filter.parse().unwrap() {
            id = Some(document.id.clone())
        }
    } else if let Some(("asc_desc_rank", filter)) = filter.split_once('>') {
        if document.asc_desc_rank > filter.parse().unwrap() {
            id = Some(document.id.clone())
        }
    } else if filter.starts_with("_geoRadius") {
        id = (document.geo_rank < 100000).then(|| document.id.clone());
    } else if filter.starts_with("NOT _geoRadius") {
        id = (document.geo_rank > 1000000).then(|| document.id.clone());
    } else if matches!(filter, "opt1 EXISTS" | "NOT opt1 NOT EXISTS") {
        id = document.opt1.is_some().then(|| document.id.clone());
    } else if matches!(filter, "NOT opt1 EXISTS" | "opt1 NOT EXISTS") {
        id = document.opt1.is_none().then(|| document.id.clone());
    } else if matches!(filter, "opt1.opt2 EXISTS") {
        if document.opt1opt2.is_some() {
            id = Some(document.id.clone());
        } else if let Some(opt1) = &document.opt1 {
            id = contains_key_rec(opt1, "opt2").then(|| document.id.clone());
        }
    } else if matches!(filter, "opt1 IS NULL" | "NOT opt1 IS NOT NULL") {
        id = document.opt1.as_ref().map_or(false, |v| v.is_null()).then(|| document.id.clone());
    } else if matches!(filter, "NOT opt1 IS NULL" | "opt1 IS NOT NULL") {
        id = document.opt1.as_ref().map_or(true, |v| !v.is_null()).then(|| document.id.clone());
    } else if matches!(filter, "opt1.opt2 IS NULL") {
        if document.opt1opt2.as_ref().map_or(false, |v| v.is_null()) {
            id = Some(document.id.clone());
        } else if let Some(opt1) = &document.opt1 {
            if !opt1.is_null() {
                id = contains_null_rec(opt1, "opt2").then(|| document.id.clone());
            }
        }
    } else if matches!(filter, "opt1 IS EMPTY" | "NOT opt1 IS NOT EMPTY") {
        id = document.opt1.as_ref().map_or(false, is_empty_value).then(|| document.id.clone());
    } else if matches!(filter, "NOT opt1 IS EMPTY" | "opt1 IS NOT EMPTY") {
        id = document
            .opt1
            .as_ref()
            .map_or(true, |v| !is_empty_value(v))
            .then(|| document.id.clone());
    } else if matches!(filter, "opt1.opt2 IS EMPTY") {
        if document.opt1opt2.as_ref().map_or(false, is_empty_value) {
            id = Some(document.id.clone());
        }
    } else if matches!(
        filter,
        "tag_in IN[1, 2, 3, four, five]" | "NOT tag_in NOT IN[1, 2, 3, four, five]"
    ) {
        id = matches!(document.id.as_str(), "A" | "B" | "C" | "D" | "E")
            .then(|| document.id.clone());
    } else if matches!(filter, "tag_in NOT IN[1, 2, 3, four, five]") {
        id = (!matches!(document.id.as_str(), "A" | "B" | "C" | "D" | "E"))
            .then(|| document.id.clone());
    }
    id
}

pub fn is_empty_value(v: &serde_json::Value) -> bool {
    match v {
        serde_json::Value::String(s) => s.is_empty(),
        serde_json::Value::Array(a) => a.is_empty(),
        serde_json::Value::Object(o) => o.is_empty(),
        _ => false,
    }
}

pub fn contains_key_rec(v: &serde_json::Value, key: &str) -> bool {
    match v {
        serde_json::Value::Array(v) => {
            for v in v.iter() {
                if contains_key_rec(v, key) {
                    return true;
                }
            }
            false
        }
        serde_json::Value::Object(v) => {
            for (k, v) in v.iter() {
                if k == key || contains_key_rec(v, key) {
                    return true;
                }
            }
            false
        }
        _ => false,
    }
}

pub fn contains_null_rec(v: &serde_json::Value, key: &str) -> bool {
    match v {
        serde_json::Value::Object(v) => {
            for (k, v) in v.iter() {
                if k == key && v.is_null() || contains_null_rec(v, key) {
                    return true;
                }
            }
            false
        }
        serde_json::Value::Array(v) => {
            for v in v.iter() {
                if contains_null_rec(v, key) {
                    return true;
                }
            }
            false
        }
        _ => false,
    }
}

pub fn expected_filtered_ids(filters: Vec<Either<Vec<&str>, &str>>) -> HashSet<String> {
    let dataset: Vec<TestDocument> =
        serde_json::Deserializer::from_str(CONTENT).into_iter().map(|r| r.unwrap()).collect();

    let mut filtered_ids: HashSet<_> = dataset.iter().map(|d| d.id.clone()).collect();
    for either in filters {
        let ids = match either {
            Left(array) => array
                .into_iter()
                .map(|f| {
                    let ids: HashSet<String> =
                        dataset.iter().filter_map(|d| execute_filter(f, d)).collect();
                    ids
                })
                .reduce(|a, b| a.union(&b).cloned().collect())
                .unwrap(),
            Right(filter) => {
                let ids: HashSet<String> =
                    dataset.iter().filter_map(|d| execute_filter(filter, d)).collect();
                ids
            }
        };

        filtered_ids = filtered_ids.intersection(&ids).cloned().collect();
    }

    filtered_ids
}

#[derive(Debug, Clone, Deserialize, PartialEq, Eq)]
pub struct TestDocument {
    pub id: String,
    pub word_rank: u32,
    pub typo_rank: u32,
    pub proximity_rank: u32,
    pub attribute_rank: u32,
    pub exact_rank: u32,
    pub asc_desc_rank: u32,
    pub sort_by_rank: u32,
    pub geo_rank: u32,
    pub title: String,
    pub description: String,
    pub tag: String,
    #[serde(default, deserialize_with = "some_option")]
    pub opt1: Option<serde_json::Value>,
    #[serde(default, deserialize_with = "some_option", rename = "opt1.opt2")]
    pub opt1opt2: Option<serde_json::Value>,
}

fn some_option<'de, D>(deserializer: D) -> Result<Option<serde_json::Value>, D::Error>
where
    D: Deserializer<'de>,
{
    let result = serde_json::Value::deserialize(deserializer)?;
    Ok(Some(result))
}

#[test]
fn basic_degraded_search() {
    use Criterion::*;
    let criteria = vec![Words, Typo, Proximity, Attribute, Exactness];
    let index = setup_search_index_with_criteria(&criteria);
    let rtxn = index.read_txn().unwrap();

    let mut search = Search::new(&rtxn, &index);
    search.query(TEST_QUERY);
    search.limit(EXTERNAL_DOCUMENTS_IDS.len());
    search.time_budget(TimeBudget::new(Duration::from_millis(0)));

    let result = search.execute().unwrap();
    assert!(result.degraded);
}

#[test]
fn degraded_search_cannot_skip_filter() {
    use Criterion::*;
    let criteria = vec![Words, Typo, Proximity, Attribute, Exactness];
    let index = setup_search_index_with_criteria(&criteria);
    let rtxn = index.read_txn().unwrap();

    let mut search = Search::new(&rtxn, &index);
    search.query(TEST_QUERY);
    search.limit(EXTERNAL_DOCUMENTS_IDS.len());
    search.time_budget(TimeBudget::new(Duration::from_millis(0)));
    let filter_condition = Filter::from_str("tag = etiopia").unwrap().unwrap();
    search.filter(filter_condition);

    let result = search.execute().unwrap();
    assert!(result.degraded);
    snapshot!(format!("{:?}\n{:?}", result.candidates, result.documents_ids), @r###"
    RoaringBitmap<[0, 2, 5, 8, 11, 14]>
    [0, 2, 5, 8, 11, 14]
    "###);
}