use crate::color::ColorConfig;

use crate::color::Effect;

use format_bytes::format_bytes;

use format_bytes::write_bytes;

use hg::config::Config;

use hg::errors::HgError;

use hg::utils::files::get_bytes_from_os_string;

use std::borrow::Cow;

use std::env;

use std::io;

use std::io::{ErrorKind, Write};

pub struct Ui {

    stdout: std::io::Stdout,

    stderr: std::io::Stderr,

    colors: Option<ColorConfig>,

}

/// The kind of user interface error

pub enum UiError {

    /// The standard output stream cannot be written to

    StdoutError(io::Error),

    /// The standard error stream cannot be written to

    StderrError(io::Error),

}

/// The commandline user interface

impl Ui {

    pub fn new(config: &Config) -> Result<Self, HgError> {

        Ok(Ui {

            // If using something else, also adapt `isatty()` below.

            stdout: std::io::stdout(),

            stderr: std::io::stderr(),

            colors: ColorConfig::new(config)?,

        })

    }

    /// Default to no color if color configuration errors.

    ///

    /// Useful when we’re already handling another error.

    pub fn new_infallible(config: &Config) -> Self {

        Ui {

            // If using something else, also adapt `isatty()` below.

            stdout: std::io::stdout(),

            stderr: std::io::stderr(),

            colors: ColorConfig::new(config).unwrap_or(None),

        }

    }

    /// Returns a buffered handle on stdout for faster batch printing

    /// operations.

    pub fn stdout_buffer(&self) -> StdoutBuffer<std::io::StdoutLock> {

        StdoutBuffer::new(self.stdout.lock())

    }

    /// Write bytes to stdout

    pub fn write_stdout(&self, bytes: &[u8]) -> Result<(), UiError> {

        let mut stdout = self.stdout.lock();

        stdout.write_all(bytes).or_else(handle_stdout_error)?;

        stdout.flush().or_else(handle_stdout_error)

    }

    /// Write bytes to stderr

    pub fn write_stderr(&self, bytes: &[u8]) -> Result<(), UiError> {

        let mut stderr = self.stderr.lock();

        stderr.write_all(bytes).or_else(handle_stderr_error)?;

        stderr.flush().or_else(handle_stderr_error)

    }

    /// Write bytes to stdout with the given label

    ///

    /// Like the optional `label` parameter in `mercurial/ui.py`,

    /// this label influences the color used for this output.

    pub fn write_stdout_labelled(

        &self,

        bytes: &[u8],

        label: &str,

    ) -> Result<(), UiError> {

        if let Some(colors) = &self.colors {

            if let Some(effects) = colors.styles.get(label.as_bytes()) {

                if !effects.is_empty() {

                    return self

                        .write_stdout_with_effects(bytes, effects)

                        .or_else(handle_stdout_error);

                }

            }

        }

        self.write_stdout(bytes)

    }

    fn write_stdout_with_effects(

        &self,

        bytes: &[u8],

        effects: &[Effect],

    ) -> io::Result<()> {

        let stdout = &mut self.stdout.lock();

        let mut write_line = |line: &[u8], first: bool| {

            // `line` does not include the newline delimiter

            if !first {

                stdout.write_all(b"\n")?;

            }

            if line.is_empty() {

                return Ok(());

            }

            /// 0x1B == 27 == 0o33

            const ASCII_ESCAPE: &[u8] = b"\x1b";

            write_bytes!(stdout, b"{}[0", ASCII_ESCAPE)?;

            for effect in effects {

                write_bytes!(stdout, b";{}", effect)?;

            }

            write_bytes!(stdout, b"m")?;

            stdout.write_all(line)?;

            write_bytes!(stdout, b"{}[0m", ASCII_ESCAPE)

        };

        let mut lines = bytes.split(|&byte| byte == b'\n');

        if let Some(first) = lines.next() {

            write_line(first, true)?;

            for line in lines {

                write_line(line, false)?

            }

        }

        stdout.flush()

    }

    /// Return whether plain mode is active.

    ///

    /// Plain mode means that all configuration variables which affect

    /// the behavior and output of Mercurial should be

    /// ignored. Additionally, the output should be stable,

    /// reproducible and suitable for use in scripts or applications.

    ///

    /// The only way to trigger plain mode is by setting either the

    /// `HGPLAIN' or `HGPLAINEXCEPT' environment variables.

    ///

    /// The return value can either be

    /// - False if HGPLAIN is not set, or feature is in HGPLAINEXCEPT

    /// - False if feature is disabled by default and not included in HGPLAIN

    /// - True otherwise

    pub fn plain(&self, feature: Option<&str>) -> bool {

        plain(feature)

    }

}

pub fn plain(opt_feature: Option<&str>) -> bool {

    if let Some(except) = env::var_os("HGPLAINEXCEPT") {

        opt_feature.map_or(true, |feature| {

            get_bytes_from_os_string(except)

                .split(|&byte| byte == b',')

                .all(|exception| exception != feature.as_bytes())

        })

    } else {

        env::var_os("HGPLAIN").is_some()

    }

}

/// A buffered stdout writer for faster batch printing operations.

pub struct StdoutBuffer<W: Write> {

    buf: io::BufWriter<W>,

}

impl<W: Write> StdoutBuffer<W> {

    pub fn new(writer: W) -> Self {

        let buf = io::BufWriter::new(writer);

        Self { buf }

    }

    /// Write bytes to stdout buffer

    pub fn write_all(&mut self, bytes: &[u8]) -> Result<(), UiError> {

        self.buf.write_all(bytes).or_else(handle_stdout_error)

    }

    /// Flush bytes to stdout

    pub fn flush(&mut self) -> Result<(), UiError> {

        self.buf.flush().or_else(handle_stdout_error)

    }

}

/// Sometimes writing to stdout is not possible, try writing to stderr to

/// signal that failure, otherwise just bail.

fn handle_stdout_error(error: io::Error) -> Result<(), UiError> {

    if let ErrorKind::BrokenPipe = error.kind() {

        // This makes `| head` work for example

        return Ok(());

    }

    let mut stderr = io::stderr();

    stderr

        .write_all(&format_bytes!(

            b"abort: {}\n",

            error.to_string().as_bytes()

        ))

        .map_err(UiError::StderrError)?;

    stderr.flush().map_err(UiError::StderrError)?;

    Err(UiError::StdoutError(error))

}

/// Sometimes writing to stderr is not possible.

fn handle_stderr_error(error: io::Error) -> Result<(), UiError> {

    // A broken pipe should not result in a error

    // like with `| head` for example

    if let ErrorKind::BrokenPipe = error.kind() {

        return Ok(());

    }

    Err(UiError::StdoutError(error))

}

/// Encode rust strings according to the user system.

pub fn utf8_to_local(s: &str) -> Cow<[u8]> {

    // TODO encode for the user's system //

    let bytes = s.as_bytes();

    Cow::Borrowed(bytes)

}

/// Should formatted output be used?

///

/// Note: rhg does not have the formatter mechanism yet,

/// but this is also used when deciding whether to use color.

pub fn formatted(config: &Config) -> Result<bool, HgError> {

    if let Some(formatted) = config.get_option(b"ui", b"formatted")? {

        Ok(formatted)

    } else {

        isatty(config)

    }

}

fn isatty(config: &Config) -> Result<bool, HgError> {

    Ok(if config.get_bool(b"ui", b"nontty")? {

        false

    } else {

        atty::is(atty::Stream::Stdout)

    })

}