//! Support for loading user defined rendering options.
//!
//! User options are given in a toml file, for example
//!
//! ```toml
//! skill_size = 20
//! ```
//!
//! The file is automatically deserialized by serde, so all fields defined in
//! [`UserOptions`](struct.UserOptions.html) can be used.
use image::Rgba;
use rusttype::Font;
use serde::{Deserialize, Serialize};
use std::{error::Error, fmt, fs, io, path::Path};

use super::render::{Alignment, RenderOptions};

/// Error that can occur during loading or converting user options.
#[derive(Debug)]
pub enum ConfigError {
    Io(io::Error),
    Serialization(toml::de::Error),
    Font(rusttype::Error),
}

error_froms! {
    ConfigError,
    err: io::Error => ConfigError::Io(err),
    err: toml::de::Error => ConfigError::Serialization(err),
    err: rusttype::Error => ConfigError::Font(err),
}

impl fmt::Display for ConfigError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "ConfigError: ")?;
        match *self {
            ConfigError::Io(_) => write!(f, "input/output error"),
            ConfigError::Serialization(_) => write!(f, "serialization error"),
            ConfigError::Font(_) => write!(f, "could not load the font"),
        }
    }
}

impl Error for ConfigError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match *self {
            ConfigError::Io(ref err) => Some(err),
            ConfigError::Serialization(ref err) => Some(err),
            ConfigError::Font(ref err) => Some(err),
        }
    }
}

macro_rules! maybe_take_from {
    (from: $from:expr, to: $to:ident, $($field:ident,)*) => {
        $(
            if let Some(data) = $from.$field {
                $to.$field = data;
            }
        )*
    }
}

/// A struct for deserializing user defined options.
///
/// This is basically a struct containing the same fields, but optional. If a field is given, it
/// should override the corresponding field in
/// [`RenderOptions`](../render/struct.RenderOptions.html).
///
/// Some fields require some pre-processing, as the proper type cannot be serialized (e.g.
/// `image::Rgba` for `background_color`).
#[derive(Debug, Serialize, Deserialize)]
pub struct UserOptions {
    pub traitline_x_offset: Option<u32>,
    pub trait_size: Option<u32>,
    pub line_color: Option<[u8; 4]>,
    pub line_height: Option<u32>,
    pub text_size: Option<u32>,
    pub background_color: Option<[u8; 4]>,
    pub font_path: Option<String>,
    pub render_specialization_names: Option<bool>,
    pub skill_alignment: Option<Alignment>,
}

impl UserOptions {
    /// Converts this `UserOptions` to a proper
    /// [`RenderOptions`](../render/struct.RenderOptions.html).
    pub fn convert(self) -> Result<RenderOptions, ConfigError> {
        let mut result = RenderOptions::default();

        if let Some(data) = self.background_color {
            result.background_color = Rgba(data);
        }

        if let Some(data) = self.line_color {
            result.line_color = Rgba(data);
        }

        if let Some(path) = self.font_path {
            let data = fs::read(path)?;
            let font = Font::from_bytes(data)?;
            result.font = font;
        }

        maybe_take_from! {
            from: self, to: result,
            traitline_x_offset,
            trait_size,
            line_height,
            text_size,
            render_specialization_names,
            skill_alignment,
        }

        Ok(result)
    }
}

/// Load user given options from the given file path.
///
/// This is basically a convenience function around reading the data, deserializing it from toml
/// and returning [`UserOptions::convert`](struct.UserOptions.html#method.convert).
pub fn load_file<P: AsRef<Path>>(path: P) -> Result<RenderOptions, ConfigError> {
    let data = fs::read(path)?;
    let opts = toml::from_slice::<UserOptions>(&data)?;
    opts.convert()
}