//! # The font file formats
//!
//! Every font or more specifically **charset** in Signum used a group of font files that
//! described the font at different resolutions. There was the `*.E24` file format used
//! for text in the editor, the `*.P24` format for 24-needle printers, the `*.P09` format
//! for 9-needle printers and the `*.L30` format for laser printers.

use std::{io, str::FromStr};

use printer::PrinterKind;
use thiserror::*;

pub mod editor;
pub mod encoding;
pub mod printer;

#[derive(Copy, Clone)]
/// A table stores which characters of a charset are used
pub struct UseTable {
    /// The number of uses per char
    pub chars: [usize; 128],
}

impl UseTable {
    /// Get the first and last char that is used
    ///
    /// ```
    /// use sdo::font::UseTable;
    /// let mut chars = [0; 128];
    /// let use_table = UseTable { chars };
    /// assert_eq!(use_table.first_last(), None);
    /// chars[5] = 1;
    /// let use_table = UseTable { chars };
    /// assert_eq!(use_table.first_last(), Some((5, 5)));
    /// chars[120] = 3;
    /// let use_table = UseTable { chars };
    /// assert_eq!(use_table.first_last(), Some((5, 120)));
    /// ```
    pub fn first_last(&self) -> Option<(u8, u8)> {
        let mut iter = self.chars.iter();
        let first_char = iter.position(|x| *x > 0)? as u8;
        let last_char = iter.rposition(|x| *x > 0).map(|x| x + 1).unwrap_or(0) as u8 + first_char;

        Some((first_char, last_char))
    }
}

impl From<&str> for UseTable {
    fn from(text: &str) -> UseTable {
        let mut chars = [0; 128];
        for c in text.chars() {
            chars[c as usize] += 1;
        }
        Self { chars }
    }
}

impl UseTable {
    /// Create a new usage table
    pub const fn new() -> Self {
        Self { chars: [0; 128] }
    }
}

/// Matrix of character usage in a single document
pub struct UseMatrix {
    /// One entry for each charset
    pub csets: [UseTable; 8],
}

impl UseMatrix {
    /// Creates a new matrix
    pub const fn new() -> Self {
        Self {
            csets: [UseTable::new(); 8],
        }
    }
}

/// List of character usage tables, for use with font caches
pub struct UseTableVec {
    /// One entry for each charset
    pub csets: Vec<UseTable>,
}

impl Default for UseTableVec {
    fn default() -> Self {
        Self::new()
    }
}

impl UseTableVec {
    /// Creates a new list
    pub fn new() -> Self {
        UseTableVec {
            csets: Vec::with_capacity(8),
        }
    }

    /// Integrate a UseMatrix (from a document) to this vector
    pub fn append(&mut self, chsets: &[Option<usize>; 8], use_matrix: UseMatrix) {
        for (cset, use_table) in use_matrix.csets.iter().enumerate() {
            if let Some(index) = chsets.get(cset).and_then(|x| *x) {
                while self.csets.len() + 1 < index {
                    self.csets.push(UseTable::new());
                }
                if self.csets.len() == index {
                    self.csets.push(*use_table);
                } else {
                    for (left, right) in self.csets[index]
                        .chars
                        .iter_mut()
                        .zip(use_table.chars.iter())
                    {
                        *left += *right
                    }
                }
            }
        }
    }
}

#[derive(Debug, Copy, Clone)]
/// A kind of font
pub enum FontKind {
    /// Font used in the signum editor (`E24`)
    Editor,
    /// Font used for printing signum documents
    Printer(PrinterKind),
}

impl FontKind {
    /// Return the number of device points corresponding to the given vertical units.
    pub fn scale_y(&self, units: u16) -> u32 {
        match self {
            Self::Editor => u32::from(units) * 2,
            Self::Printer(pk) => pk.scale_y(units),
        }
    }

    /// Return the number of device points corresponding to the given horizontal units.
    pub fn scale_x(&self, units: u16) -> u32 {
        match self {
            Self::Editor => u32::from(units),
            Self::Printer(pk) => pk.scale_x(units),
        }
    }

    /// Returns the amount of pixels from the top of the box to
    /// the baseline of the font.
    pub fn baseline(&self) -> i16 {
        match self {
            Self::Editor => 18,
            Self::Printer(pk) => pk.baseline(),
        }
    }

    /// Return the resolution (in DPI per direction)
    pub fn resolution(&self) -> (isize, isize) {
        match self {
            Self::Editor => (104, 90),
            Self::Printer(PrinterKind::Needle9) => (216, 216),
            Self::Printer(PrinterKind::Needle24) => (360, 360),
            Self::Printer(PrinterKind::Laser30) => (300, 300),
        }
    }

    /// Get the scale that needs to be applied to the font to
    /// get the correct resoltion.
    ///
    /// FIXME: Make this part of the font matrix?
    pub fn scale(&self) -> f32 {
        match self {
            Self::Printer(pk) => pk.scale(),
            Self::Editor => todo!(),
        }
    }

    /// Get the file extension use for this format
    pub fn extension(&self) -> &'static str {
        match self {
            Self::Editor => "E24",
            Self::Printer(p) => p.extension(),
        }
    }
}

#[derive(Debug, Error)]
#[error("Unknown print driver!")]
/// Error for font kinds
pub struct UnknownFontKind {}

impl FromStr for FontKind {
    type Err = UnknownFontKind;

    fn from_str(input: &str) -> Result<Self, Self::Err> {
        match input {
            "P09" => Ok(Self::Printer(PrinterKind::Needle9)),
            "E24" => Ok(Self::Editor),
            "P24" => Ok(Self::Printer(PrinterKind::Needle24)),
            "L30" => Ok(Self::Printer(PrinterKind::Laser30)),
            _ => Err(UnknownFontKind {}),
        }
    }
}

#[derive(Debug, Error)]
/// Error when loading
pub enum LoadError {
    /// The IO failed
    #[error("Failed IO")]
    Io(#[from] io::Error),
    /// The parsing failed
    #[error("Parsing failed: {0}")]
    Parse(String),
}