/*
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. 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.
 */

/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 *
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

use super::Step;
use crate::step::Expr;
use anyhow::anyhow;
use proc_macro2::{Span, TokenStream};
use quote::{quote, ToTokens, TokenStreamExt};
use serde_yaml::Value;

pub const OPERATORS: [&str; 4] = ["lt", "lte", "gt", "gte"];

pub struct Comparison {
    pub(crate) expr: Expr,
    value: Value,
    op: String,
}

impl From<Comparison> for Step {
    fn from(comparison: Comparison) -> Self {
        Step::Comparison(comparison)
    }
}

impl Comparison {
    pub fn try_parse(yaml: &Value, op: &str) -> anyhow::Result<Comparison> {
        let hash = yaml
            .as_mapping()
            .ok_or_else(|| anyhow!("expected hash but found {:?}", yaml))?;

        let (k, v) = hash.iter().next().unwrap();
        let expr = k
            .as_str()
            .ok_or_else(|| anyhow!("expected string key but found {:?}", k))?;

        Ok(Comparison {
            expr: expr.into(),
            value: v.clone(),
            op: op.into(),
        })
    }

    fn assert<T: PartialOrd + ToTokens>(
        &self,
        t: T,
        expr: TokenStream,
        op: syn::BinOp,
        tokens: &mut TokenStream,
    ) {
        tokens.append_all(quote! {
            crate::assert_comparison!(&json#expr, #op #t);
        });
    }
}

impl ToTokens for Comparison {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        let expr = self.expr.expression();
        let op = match self.op.as_str() {
            "lte" => syn::BinOp::Le(syn::token::Le(Span::call_site())),
            "lt" => syn::BinOp::Lt(syn::token::Lt(Span::call_site())),
            "gt" => syn::BinOp::Gt(syn::token::Gt(Span::call_site())),
            "gte" => syn::BinOp::Ge(syn::token::Ge(Span::call_site())),
            n => panic!("unsupported op {}", n),
        };

        match self.value.as_i64() {
            Some(i) => self.assert(i, expr, op, tokens),
            None => match self.value.as_f64() {
                Some(f) => self.assert(f, expr, op, tokens),
                None => {
                    match self.value.as_str() {
                        // handle "set" values
                        Some(s) if s.starts_with('$') => {
                            let s = s
                                .trim_start_matches('$')
                                .trim_start_matches('{')
                                .trim_end_matches('}');
                            let ident = syn::Ident::new(s, Span::call_site());
                            tokens.append_all(quote! {
                                crate::assert_comparison_from_set_value!(&json#expr, #op #ident);
                            });
                        }
                        _ => panic!("Expected i64 or f64 but found {:?}", &self.value),
                    }
                }
            },
        }
    }
}