extern crate reqwest;
extern crate serde_json;

use serde_json::Value;
use std::fmt::{Display, Error, Formatter};

const PROBLEMS_URL: &str = "https://leetcode.cn/api/problems/algorithms/";
const GRAPHQL_URL: &str = "https://leetcode.cn/graphql";
const QUESTION_QUERY_STRING: &str = r#"
query questionData($titleSlug: String!) {
    question(titleSlug: $titleSlug) {
        content
        stats
        codeDefinition
        sampleTestCase
        metaData
    }
}"#;
const QUESTION_QUERY_OPERATION: &str = "questionData";

pub async fn get_problem(frontend_question_id: u32) -> Option<Problem> {
    let problems = get_problems().await.unwrap();
    for problem in problems.stat_status_pairs.iter() {
        match problem.stat.frontend_question_id.parse::<u32>() {
            Ok(id) => {
                if id == frontend_question_id {
                    if problem.paid_only {
                        return None;
                    }

                    let client = reqwest::Client::new();
                    let resp: RawProblem =  client
                        .post(GRAPHQL_URL)
                        .json(&Query::question_query(
                            problem.stat.question_title_slug.as_ref().unwrap(),
                        ))
                        .send()
                        .await
                        .unwrap()
                        .json()
                        .await
                        .unwrap();
                    return Some(Problem {
                        title: problem.stat.question_title.clone().unwrap(),
                        title_slug: problem.stat.question_title_slug.clone().unwrap(),
                        code_definition: serde_json::from_str(&resp.data.question.code_definition).unwrap(),
                        content: resp.data.question.content,
                        sample_test_case: resp.data.question.sample_test_case,
                        difficulty: problem.difficulty.to_string(),
                        question_id: id,
                        return_type: {
                            let v: Value = serde_json::from_str(&resp.data.question.meta_data).unwrap();
                            v["return"]["type"].to_string().replace("\"", "")
                        },
                    });
                }
            }
            _ => {}
        }
    }
    None
}

pub async fn get_problem_async(problem_stat: StatWithStatus) -> Option<Problem> {
    if problem_stat.paid_only {
        println!(
            "Problem {} is paid-only",
            &problem_stat.stat.frontend_question_id
        );
        return None;
    }
    let resp = surf::post(GRAPHQL_URL).body_json(&Query::question_query(
        problem_stat.stat.question_title_slug.as_ref().unwrap(),
    ));
    if resp.is_err() {
        println!(
            "Problem {} not initialized due to some error",
            &problem_stat.stat.frontend_question_id
        );
        return None;
    }
    let resp = resp.unwrap().recv_json().await;
    if resp.is_err() {
        println!(
            "Problem {} not initialized due to some error",
            &problem_stat.stat.frontend_question_id
        );
        return None;
    }
    let resp: RawProblem = resp.unwrap();
    match problem_stat.stat.frontend_question_id.parse::<u32>() {
        Ok(id) => {
            return Some(Problem {
                title: problem_stat.stat.question_title.clone().unwrap(),
                title_slug: problem_stat.stat.question_title_slug.clone().unwrap(),
                code_definition: serde_json::from_str(&resp.data.question.code_definition).unwrap(),
                content: resp.data.question.content,
                sample_test_case: resp.data.question.sample_test_case,
                difficulty: problem_stat.difficulty.to_string(),
                question_id: id,
                return_type: {
                    let v: Value = serde_json::from_str(&resp.data.question.meta_data).unwrap();
                    v["return"]["type"].to_string().replace("\"", "")
                },
            });
        }
        _ => {
            None
        }
    }
}

pub async fn get_problems() -> Option<Problems> {
    reqwest::get(PROBLEMS_URL).await.unwrap().json().await.unwrap()
}

#[derive(Serialize, Deserialize)]
pub struct Problem {
    pub title: String,
    pub title_slug: String,
    pub content: String,
    #[serde(rename = "codeDefinition")]
    pub code_definition: Vec<CodeDefinition>,
    #[serde(rename = "sampleTestCase")]
    pub sample_test_case: String,
    pub difficulty: String,
    pub question_id: u32,
    pub return_type: String,
}

#[derive(Serialize, Deserialize)]
pub struct CodeDefinition {
    pub value: String,
    pub text: String,
    #[serde(rename = "defaultCode")]
    pub default_code: String,
}

#[derive(Debug, Serialize, Deserialize)]
struct Query {
    #[serde(rename = "operationName")]
    operation_name: String,
    variables: serde_json::Value,
    query: String,
}

impl Query {
    fn question_query(title_slug: &str) -> Query {
        Query {
            operation_name: QUESTION_QUERY_OPERATION.to_owned(),
            variables: json!({ "titleSlug": title_slug }),
            query: QUESTION_QUERY_STRING.to_owned(),
        }
    }
}

#[derive(Debug, Serialize, Deserialize)]
struct RawProblem {
    data: Data,
}

#[derive(Debug, Serialize, Deserialize)]
struct Data {
    question: Question,
}

#[derive(Debug, Serialize, Deserialize)]
struct Question {
    content: String,
    stats: String,
    #[serde(rename = "codeDefinition")]
    code_definition: String,
    #[serde(rename = "sampleTestCase")]
    sample_test_case: String,
    #[serde(rename = "metaData")]
    meta_data: String,
}

#[derive(Debug, Serialize, Deserialize)]
pub struct Problems {
    user_name: String,
    num_solved: u32,
    num_total: u32,
    ac_easy: u32,
    ac_medium: u32,
    ac_hard: u32,
    pub stat_status_pairs: Vec<StatWithStatus>,
}

#[derive(Debug, Serialize, Deserialize)]
pub struct StatWithStatus {
    pub stat: Stat,
    difficulty: Difficulty,
    paid_only: bool,
    is_favor: bool,
    frequency: u32,
    progress: u32,
}

#[derive(Debug, Serialize, Deserialize)]
pub struct Stat {
    question_id: u32,
    #[serde(rename = "question__article__slug")]
    question_article_slug: Option<String>,
    #[serde(rename = "question__title")]
    question_title: Option<String>,
    #[serde(rename = "question__title_slug")]
    question_title_slug: Option<String>,
    #[serde(rename = "question__hide")]
    question_hide: bool,
    total_acs: u32,
    total_submitted: u32,
    pub frontend_question_id: String,
    is_new_question: bool,
}

#[derive(Debug, Serialize, Deserialize)]
struct Difficulty {
    level: u32,
}

impl Display for Difficulty {
    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
        match self.level {
            1 => f.write_str("Easy"),
            2 => f.write_str("Medium"),
            3 => f.write_str("Hard"),
            _ => f.write_str("Unknown"),
        }
    }
}