use async_graphql::{Context, EmptySubscription, Object, Result, Schema};
use async_std::sync::RwLock;
use serde_json;

#[derive(Clone)]
struct Table {
    name: String,
}

impl Table {
    async fn new(name: String) -> Self {
        Self { name: name }
    }
}

#[Object]
impl Table {
    async fn name(&self) -> String {
        self.name.to_string()
    }
}

struct Query;

#[Object]
impl Query {
    async fn table(&self, ctx: &Context<'_>, name: String) -> Result<Option<Table>> {
        let tbls = ctx
            .data::<RwLock<Vec<Table>>>()
            .unwrap()
            .read()
            .await
            .to_vec();
        let idx = tbls.binary_search_by(|t| t.name.cmp(&name)).unwrap();
        Ok(Some(tbls[idx].clone()))
    }

    async fn tables(&self, ctx: &Context<'_>) -> Vec<Table> {
        ctx.data::<RwLock<Vec<Table>>>()
            .unwrap()
            .read()
            .await
            .to_vec()
    }
}

struct Mutation;

#[Object]
impl Mutation {
    async fn create_table(&self, ctx: &Context<'_>, name: String) -> Result<Option<Table>> {
        let mut tables = ctx.data::<RwLock<Vec<Table>>>().unwrap().write().await;
        let output = Table::new(name).await;
        tables.push(output.clone());
        tables.sort_by_key(|k| k.name.clone());
        Ok(Some(output))
    }
}

#[derive(Clone)]
pub struct Database {
    schema: Schema<Query, Mutation, EmptySubscription>,
}

impl Database {
    pub fn new() -> Self {
        let tables: Vec<Table> = Vec::new();
        Self {
            schema: Schema::build(Query, Mutation, EmptySubscription)
                .data(RwLock::new(tables))
                .finish(),
        }
    }

    pub async fn execute(&self, qry: &str) -> String {
        let res = self.schema.execute(qry).await;
        serde_json::to_string(&res).unwrap()
    }
}

#[cfg(test)]
mod support {
    use super::*;

    pub fn compare(db: &Database, output: &str, expected: &str) {
        assert!(
            output == expected,
            "\n\n{}\nGot:  {}\nWant: {}\n\n",
            db.schema.sdl(),
            output,
            expected
        );
    }
}

#[cfg(test)]
mod queries {
    use super::*;

    #[async_std::test]
    async fn list_table() {
        let db = Database::new();
        db.execute(r#"mutation {createTable(name: "wilma"){name}}"#)
            .await;
        db.execute(r#"mutation {createTable(name: "betty"){name}}"#)
            .await;
        let output = db.execute(r#"{table(name: "wilma"){name}}"#).await;
        let expected = r#"{"data":{"table":{"name":"wilma"}}}"#;
        support::compare(&db, &output, &expected);
    }

    #[async_std::test]
    async fn list_tables() {
        let db = Database::new();
        db.execute(r#"mutation {createTable(name: "fred"){name}}"#)
            .await;
        db.execute(r#"mutation {createTable(name: "barney"){name}}"#)
            .await;
        let output = db.execute(r#"{tables{name}}"#).await;
        let expected = r#"{"data":{"tables":[{"name":"barney"},{"name":"fred"}]}}"#;
        support::compare(&db, &output, &expected);
    }
}

#[cfg(test)]
mod mutations {
    use super::*;

    #[async_std::test]
    async fn add_table() {
        let db = Database::new();
        let output = db
            .execute(r#"mutation {createTable(name: "william"){name}}"#)
            .await;
        let expected = r#"{"data":{"createTable":{"name":"william"}}}"#;
        println!("{}", &db.schema.sdl());
        support::compare(&db, &output, &expected);
    }
}