//! Copied from
//! https://github.com/rust-lang/rust/blob/6b3ae3f6e45a33c2d95fa0362c9b2593e567fd34/library/core/src/fmt/builders.rs#L102

// Copyright (c) The Rust Project Contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

use std::fmt;

pub struct PadAdapter<'buf, 'state> {
    buf: &'buf mut (dyn fmt::Write + 'buf),
    state: &'state mut PadAdapterState,
}

pub struct PadAdapterState {
    on_newline: bool,
}

impl Default for PadAdapterState {
    fn default() -> Self {
        PadAdapterState { on_newline: true }
    }
}

impl<'buf, 'state> PadAdapter<'buf, 'state> {
    pub fn wrap<'slot, 'fmt: 'buf + 'slot>(
        fmt: &'fmt mut fmt::Formatter<'_>,
        state: &'state mut PadAdapterState,
    ) -> Self {
        PadAdapter { buf: fmt, state }
    }
}

impl fmt::Write for PadAdapter<'_, '_> {
    fn write_str(&mut self, s: &str) -> fmt::Result {
        for s in s.split_inclusive('\n') {
            if self.state.on_newline {
                self.buf.write_str("    ")?;
            }
            self.state.on_newline = s.ends_with('\n');
            self.buf.write_str(s)?;
        }
        Ok(())
    }

    fn write_char(&mut self, c: char) -> fmt::Result {
        if self.state.on_newline {
            self.buf.write_str("    ")?;
        }
        self.state.on_newline = c == '\n';
        self.buf.write_char(c)
    }
}