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/*
 * Copyright (C) 2022 Vaticle
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 */

use std::{collections::HashSet, fmt};

use itertools::Itertools;

use crate::{
    common::{
        error::{collect_err, TypeQLError},
        token,
        validatable::Validatable,
        Result,
    },
    pattern::{Conjunction, VariablesRetrieved},
    query::{
        modifier::{Modifiers, Sorting},
        AggregateQueryBuilder, MatchClause, TypeQLGetGroup,
    },
    variable::{variable::VariableRef, Variable},
    write_joined,
};

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct TypeQLGet {
    pub match_clause: MatchClause,
    pub filter: Filter,
    pub modifiers: Modifiers,
}

impl AggregateQueryBuilder for TypeQLGet {}

impl TypeQLGet {
    pub fn new(match_clause: MatchClause) -> Self {
        TypeQLGet { match_clause, filter: Filter::default(), modifiers: Modifiers::default() }
    }

    pub fn sort(self, sorting: impl Into<Sorting>) -> Self {
        TypeQLGet { modifiers: self.modifiers.sort(sorting), ..self }
    }

    pub fn limit(self, limit: usize) -> Self {
        TypeQLGet { modifiers: self.modifiers.limit(limit), ..self }
    }

    pub fn offset(self, offset: usize) -> Self {
        TypeQLGet { modifiers: self.modifiers.offset(offset), ..self }
    }

    pub fn group(self, var: impl Into<Variable>) -> TypeQLGetGroup {
        TypeQLGetGroup { query: self, group_var: var.into() }
    }
}

impl Validatable for TypeQLGet {
    fn validate(&self) -> Result {
        let match_variables = self.match_clause.retrieved_variables().collect();
        let filter_vars = HashSet::from_iter((&self.filter.vars).iter().map(Variable::as_ref));
        let retrieved_variables = if self.filter.vars.is_empty() { &match_variables } else { &filter_vars };
        collect_err([
            self.match_clause.validate(),
            validate_filters_are_in_scope(&match_variables, &self.filter),
            self.modifiers.sorting.as_ref().map(|s| s.validate(&retrieved_variables)).unwrap_or(Ok(())),
            validate_variable_names_are_unique(&self.match_clause.conjunction),
        ])
    }
}

impl VariablesRetrieved for TypeQLGet {
    fn retrieved_variables(&self) -> Box<dyn Iterator<Item = VariableRef<'_>> + '_> {
        if !self.filter.vars.is_empty() {
            Box::new(self.filter.vars.iter().map(|v| v.as_ref()))
        } else {
            self.match_clause.retrieved_variables()
        }
    }
}

fn validate_filters_are_in_scope(match_variables: &HashSet<VariableRef<'_>>, filter: &Filter) -> Result {
    let mut seen = HashSet::new();
    collect_err(filter.vars.iter().map(|r| {
        if !r.is_name() {
            Err(TypeQLError::VariableNotNamed().into())
        } else if !match_variables.contains(&r.as_ref()) {
            Err(TypeQLError::GetVarNotBound(r.to_owned()).into())
        } else if seen.contains(&r) {
            Err(TypeQLError::GetVarRepeating(r.to_owned()).into())
        } else {
            seen.insert(r);
            Ok(())
        }
    }))
}

fn validate_variable_names_are_unique(conjunction: &Conjunction) -> Result {
    let all_refs = conjunction.variables_recursive();
    let (concept_refs, value_refs): (HashSet<VariableRef<'_>>, HashSet<VariableRef<'_>>) =
        all_refs.partition(|r| r.is_concept());
    let concept_names = concept_refs.iter().map(|r| r).collect::<HashSet<_>>();
    let value_names = value_refs.iter().map(|r| r).collect::<HashSet<_>>();
    let common_refs = concept_names.intersection(&value_names).collect::<HashSet<_>>();
    if !common_refs.is_empty() {
        return Err(TypeQLError::VariableNameConflict(common_refs.iter().map(|r| r.to_string()).join(", ")).into());
    }
    Ok(())
}

impl fmt::Display for TypeQLGet {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.match_clause)?;
        write!(f, "\n{}", self.filter)?;
        if !self.modifiers.is_empty() {
            write!(f, "\n{}", self.modifiers)
        } else {
            Ok(())
        }
    }
}

#[derive(Clone, Debug, Eq, PartialEq, Default)]
pub struct Filter {
    pub vars: Vec<Variable>,
}

impl fmt::Display for Filter {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", token::Clause::Get)?;
        if !self.vars.is_empty() {
            write!(f, " ")?;
            write_joined!(f, ", ", self.vars)?;
        }
        write!(f, ";")
    }
}