morethantext-web/src/database/database.rs

use async_std::sync::{Arc, RwLock};
use std::{collections::HashMap, error::Error, fmt, str::FromStr};

#[derive(Debug)]
pub struct DBError {
    detail: String,
    source: Option<Box<DBError>>,
}

impl DBError {
    fn new(detail: String) -> Self {
        Self {
            detail: detail.to_string(),
            source: None,
        }
    }
}

impl fmt::Display for DBError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", &self.detail)
    }
}

impl Error for DBError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match &self.source {
            Some(err) => Some(err),
            None => None,
        }
    }
}

#[derive(Clone, PartialEq)]
pub enum FieldType {
    Table,
}

impl fmt::Display for FieldType {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            FieldType::Table => write!(f, "table"),
        }
    }
}

impl FromStr for FieldType {
    type Err = DBError;

    fn from_str(input: &str) -> Result<FieldType, Self::Err> {
        match input {
            "table" => Ok(FieldType::Table),
            _ => Err(DBError::new(format!("field type {} does not exist", input))),
        }
    }
}

pub struct Table {
    fields: Arc<RwLock<HashMap<String, FieldType>>>,
}

impl Table {
    pub async fn new() -> Self {
        Self {
            fields: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    pub async fn add_field(&self, name: &str, ftype: &str) -> Result<(), Box<dyn Error>> {
        let ftype = match FieldType::from_str(ftype) {
            Ok(field) => field,
            Err(err) => {
                let mut error = DBError::new(format!("failed to add field {}", name));
                error.source = Some(Box::new(err));
                return Err(Box::new(error));
            }
        };
        let mut fmap = self.fields.write().await;
        match fmap.get(name) {
            Some(_) => Err(Box::new(DBError::new(format!(
                "field {} already exists",
                name
            )))),
            None => {
                fmap.insert(name.to_string(), ftype);
                Ok(())
            }
        }
    }

    pub async fn fields(&self) -> HashMap<String, FieldType> {
        let fmap = self.fields.read().await;
        fmap.clone()
    }
}

pub struct Database;

impl Database {
    pub async fn new() -> Self {
        Self {}
    }

    pub async fn add_table(&self, _name: String) -> Table {
        Table::new().await
    }
}

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

    #[async_std::test]
    async fn new_table() {
        Table::new().await;
    }

    #[async_std::test]
    async fn add_field() {
        let table = Table::new().await;
        let mut expected: HashMap<String, FieldType> = HashMap::new();
        expected.insert("stan".to_string(), FieldType::Table);
        expected.insert("lee".to_string(), FieldType::Table);
        table.add_field("stan", "table").await.unwrap();
        table.add_field("lee", "table").await.unwrap();
        let output = table.fields().await;
        assert!(output == expected, "Table did not get the fields added.");
    }

    #[async_std::test]
    async fn add_bad_field() -> Result<(), String> {
        let table = Table::new().await;
        let name = "failure";
        let bad_type = "ljksdbtt";
        let expected = format!("failed to add field {}", name);
        let source = format!("field type {} does not exist", bad_type);
        match table.add_field(name, bad_type).await {
            Ok(_) => Err("A bad field type should not return successfully".to_string()),
            Err(err) => {
                if format!("{}", err) != expected {
                    Err(format!("Got: '{}' - Want: '{}'", err, expected))
                } else if format!("{}", err.source().unwrap()) != source {
                    Err(format!(
                        "Got: '{}' - Want: '{}'",
                        err.source().unwrap(),
                        source
                    ))
                } else {
                    Ok(())
                }
            }
        }
    }

    #[async_std::test]
    async fn add_duplicate_field() -> Result<(), String> {
        let table = Table::new().await;
        let name = "twice";
        let expected = format!("field {} already exists", name);
        table.add_field(name, "table").await.unwrap();
        match table.add_field(name, "table").await {
            Ok(_) => Err(format!("Cannot have two fields with named '{}'", name)),
            Err(err) => {
                if format!("{}", err) == expected {
                    Ok(())
                } else {
                    Err(format!("Got: '{}' - Want: '{}'", err, expected))
                }
            }
        }
    }
}

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

    #[async_std::test]
    async fn new_database() {
        Database::new().await;
    }

    #[async_std::test]
    async fn add_table() {
        let db = Database::new().await;
        db.add_table("fred".to_string()).await;
    }
}

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

    fn get_field_map() -> HashMap<String, FieldType> {
        let mut fields: HashMap<String, FieldType> = HashMap::new();
        fields.insert("table".to_string(), FieldType::Table);
        return fields;
    }

    #[test]
    fn convert_to_string() {
        for (key, value) in get_field_map().iter() {
            assert!(
                key == &value.to_string(),
                "\n\nGot:  {}\nWant: {}\n\n",
                value.to_string(),
                key
            );
        }
    }

    #[test]
    fn convert_from_string() {
        for (key, value) in get_field_map().iter() {
            assert!(
                &FieldType::from_str(key).unwrap() == value,
                "\n\nDid not return a FieldType::{}",
                key
            );
        }
    }

    #[test]
    fn convert_from_string_error() -> Result<(), String> {
        let ftype = "lkjsdfh";
        let expected = format!("field type {} does not exist", ftype);
        match FieldType::from_str(ftype) {
            Ok(_) => Err(format!("Found field type {}", ftype)),
            Err(err) => {
                if format!("{}", err) == expected {
                    Ok(())
                } else {
                    Err(format!("Got: '{}' - Want: '{}'", err, expected))
                }
            }
        }
    }
}