notmongo 0.1.5

In-process, bad database with an API similar to MongoDB
Documentation 
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use crate::{helpers, parsing};
use bson;
use bson::Bson;
use std::fmt;

enum UpdateOperator {
    Set(bson::Document),
    Unset(Vec<String>),
}

impl UpdateOperator {
    pub(crate) fn apply_inplace(&self, value: &mut bson::Document) {
        match self {
            UpdateOperator::Set(updates) => {
                // TODO: Handle names with a dot inside
                for (key, new_value) in updates.iter() {
                    value.insert(key, new_value.clone());
                }
            }
            UpdateOperator::Unset(keys) => {
                for key in keys {
                    value.remove(key);
                }
            }
        }
    }

    fn to_bson(&self) -> bson::Document {
        match self {
            UpdateOperator::Set(updates) => bson::doc! {
                "$set": updates.clone()
            },
            UpdateOperator::Unset(names_str) => {
                let names_bson = Bson::Array(
                    names_str
                        .iter()
                        .map(|name| Bson::String(name.clone()))
                        .collect(),
                );

                bson::doc! {
                    "$unset": names_bson
                }
            }
        }
    }
}

fn parse_update_operator(name: &str, argument: &Bson) -> Result<UpdateOperator, String> {
    match name {
        "$set" => {
            let updates = parsing::ensure_is_object(argument, "argument to $set")?;
            Ok(UpdateOperator::Set(updates.clone()))
        }
        "$unset" => {
            // The argument can either be a String, or an array of strings.
            let names: Vec<String> = match argument {
                Bson::Array(names_bson) => {
                    let mut names_str: Vec<String> = Vec::with_capacity(names_bson.len());

                    for name in names_bson {
                        let name = parsing::ensure_is_str(name, "argument to $unset")?.to_string();
                        names_str.push(name);
                    }

                    names_str
                }
                Bson::String(name) => vec![name.clone()],
                _ => {
                    return Err(format!(
                        "argument to $unset must be a string or array of strings, not {}",
                        argument
                    ));
                }
            };

            Ok(UpdateOperator::Unset(names))
        }
        name => Err(format!("Unsupported update operator `{}`", name)),
    }
}

pub struct UpdateQuery {
    operators: Vec<UpdateOperator>,
}

impl UpdateQuery {
    pub fn new_nop() -> UpdateQuery {
        UpdateQuery {
            operators: Vec::new(),
        }
    }

    pub fn parse_bson<B: Into<Bson>>(query: B) -> Result<UpdateQuery, String> {
        let query: Bson = query.into();
        let query = parsing::ensure_is_object(&query, "update query")?;
        let mut result = UpdateQuery::new_nop();

        for (op_name, op_arg) in query.iter() {
            result
                .operators
                .push(parse_update_operator(op_name, op_arg)?);
        }

        Ok(result)
    }

    pub fn to_bson(&self) -> bson::Document {
        let mut result = bson::Document::new();

        for operator in self.operators.iter() {
            for (op_name, op_arg) in operator.to_bson().iter() {
                result.insert(op_name, op_arg);
            }
        }

        result
    }

    pub(crate) fn apply_inplace(&self, value: &mut bson::Document) {
        for op in &self.operators {
            op.apply_inplace(value);
        }
    }

    pub(crate) fn apply_to_empty(&self) -> bson::Document {
        let mut result = bson::Document::new();
        self.apply_inplace(&mut result);
        result
    }
}

impl fmt::Display for UpdateQuery {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
        let as_bson = self.to_bson();
        write!(
            f,
            "{}",
            helpers::dump_to_json_string(as_bson.into(), true, true).unwrap()
        )
    }
}