// Copyright (C) 2022  Tassilo Horn <tsdh@gnu.org>
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program.  If not, see <https://www.gnu.org/licenses/>.

//! Provides runtime formatting of strings since our format strings are read
//! from the swayr config, not specified as literals, e.g., `{name:{:.30}}` in
//! `format.window_format`.

use rt_format::{
    Format, FormatArgument, NoNamedArguments, ParsedFormat, Specifier,
};
use std::fmt;

pub enum FmtArg {
    I64(i64),
    F64(f64),
    F32(f32),
    String(String),
}

impl From<i64> for FmtArg {
    fn from(x: i64) -> FmtArg {
        FmtArg::I64(x)
    }
}

impl From<f64> for FmtArg {
    fn from(x: f64) -> FmtArg {
        FmtArg::F64(x)
    }
}

impl From<f32> for FmtArg {
    fn from(x: f32) -> FmtArg {
        FmtArg::F32(x)
    }
}

impl From<&str> for FmtArg {
    fn from(x: &str) -> FmtArg {
        FmtArg::String(x.to_string())
    }
}

impl From<String> for FmtArg {
    fn from(x: String) -> FmtArg {
        FmtArg::String(x)
    }
}

impl ToString for FmtArg {
    fn to_string(&self) -> String {
        match self {
            FmtArg::String(x) => x.clone(),
            FmtArg::I64(x) => x.to_string(),
            FmtArg::F64(x) => x.to_string(),
            FmtArg::F32(x) => x.to_string(),
        }
    }
}

impl FormatArgument for FmtArg {
    fn supports_format(&self, spec: &Specifier) -> bool {
        spec.format == Format::Display
    }

    fn fmt_display(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            Self::String(val) => fmt::Display::fmt(&val, f),
            Self::I64(val) => fmt::Display::fmt(&val, f),
            Self::F64(val) => fmt::Display::fmt(&val, f),
            Self::F32(val) => fmt::Display::fmt(&val, f),
        }
    }

    fn fmt_debug(&self, _f: &mut fmt::Formatter) -> fmt::Result {
        Err(fmt::Error)
    }

    fn fmt_octal(&self, _f: &mut fmt::Formatter) -> fmt::Result {
        Err(fmt::Error)
    }

    fn fmt_lower_hex(&self, _f: &mut fmt::Formatter) -> fmt::Result {
        Err(fmt::Error)
    }

    fn fmt_upper_hex(&self, _f: &mut fmt::Formatter) -> fmt::Result {
        Err(fmt::Error)
    }

    fn fmt_binary(&self, _f: &mut fmt::Formatter) -> fmt::Result {
        Err(fmt::Error)
    }

    fn fmt_lower_exp(&self, _f: &mut fmt::Formatter) -> fmt::Result {
        Err(fmt::Error)
    }

    fn fmt_upper_exp(&self, _f: &mut fmt::Formatter) -> fmt::Result {
        Err(fmt::Error)
    }
}

pub fn format(fmt: &str, arg: FmtArg, clipped_str: &str) -> String {
    let arg_string = arg.to_string();

    if let Ok(pf) = ParsedFormat::parse(fmt, &[arg], &NoNamedArguments) {
        let mut s = format!("{}", pf);

        if !clipped_str.is_empty() && !s.contains(arg_string.as_str()) {
            remove_last_n_chars(&mut s, clipped_str.chars().count());
            s.push_str(clipped_str);
        }
        s
    } else {
        format!("Invalid format string: {}", fmt)
    }
}

fn remove_last_n_chars(s: &mut String, n: usize) {
    match s.char_indices().nth_back(n) {
        Some((pos, ch)) => s.truncate(pos + ch.len_utf8()),
        None => s.clear(),
    }
}

#[test]
fn test_format() {
    assert_eq!(format("{:.10}", "sway", ""), "sway");
    assert_eq!(format("{:.10}", "sway", "…"), "sway");
    assert_eq!(format("{:.4}", "𝔰𝔴𝔞𝔶", "……"), "𝔰𝔴𝔞𝔶");

    assert_eq!(format("{:.3}", "sway", ""), "swa");
    assert_eq!(format("{:.3}", "sway", "…"), "sw…");
    assert_eq!(format("{:.5}", "𝔰𝔴𝔞𝔶 𝔴𝔦𝔫𝔡𝔬𝔴", "…?"), "𝔰𝔴𝔞…?");
    assert_eq!(format("{:.5}", "sway window", "..."), "sw...");
    assert_eq!(format("{:.2}", "sway", "..."), "...");
}