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//! enable feature `adapt` to use this module
//!
//! adapt mod will help to transform the format of a Markdown's front matters

mod json;
mod toml;
mod yaml;

use crate::Markdown;
use serde::{Deserialize, Serialize};

pub use self::json::JsonAdapter;
pub use self::toml::TomlAdapter;
pub use self::yaml::YamlAdapter;

/// MDAdapter trait
/// can transform the format of a Markdown into the given kind
pub trait Adapter {
    fn adapt<T>(&self, md: Markdown) -> crate::MarkdownResult
    where
        T: AdapterObject;
}

pub trait AdapterObject: serde::ser::Serialize + serde::de::DeserializeOwned {}
/// the most common format of front matters
///
/// must have `date` and `title` field
///
/// unless will have an error
#[derive(Serialize, Deserialize, Debug)]
pub struct CommonObject {
    /// required field
    date: ::toml::value::Datetime,
    /// required field
    title: String,
    /// optional field
    tags: Option<Vec<String>>,
    /// optional field
    categories: Option<Vec<String>>,
}

impl AdapterObject for CommonObject {}

/// the all optional format of front matters
///
/// even if unexpected data is given
///
/// it will safely return an none struct
#[derive(Serialize, Deserialize, Debug)]
pub struct SafeObject {
    date: Option<String>,
    /// required field
    title: Option<String>,
    /// optional field
    tags: Option<Vec<String>>,
    /// optional field
    categories: Option<Vec<String>>,
}

impl AdapterObject for SafeObject {}

#[derive(Serialize, Deserialize, Debug)]
/// empty object
///
/// using it for test reason
pub struct EmptyObject {}

impl AdapterObject for EmptyObject {}