use std::io;
use termcolor::{Color, ColorSpec};

use crate::diagnostic::{LabelStyle, Severity};

/// Configures how a diagnostic is rendered.
#[derive(Clone, Debug)]
pub struct Config {
    /// The display style to use when rendering diagnostics.
    /// Defaults to: [`DisplayStyle::Rich`].
    ///
    /// [`DisplayStyle::Rich`]: DisplayStyle::Rich
    pub display_style: DisplayStyle,
    /// Column width of tabs.
    /// Defaults to: `4`.
    pub tab_width: usize,
    /// Styles to use when rendering the diagnostic.
    pub styles: Styles,
    /// Characters to use when rendering the diagnostic.
    pub chars: Chars,
}

impl Default for Config {
    fn default() -> Config {
        Config {
            display_style: DisplayStyle::Rich,
            tab_width: 4,
            styles: Styles::default(),
            chars: Chars::default(),
        }
    }
}

impl Config {
    /// Measure the unicode width of a character, taking into account the tab width.
    pub fn width(&self, ch: char) -> usize {
        use unicode_width::UnicodeWidthChar;

        match ch {
            '\t' => self.tab_width,
            _ => ch.width().unwrap_or(0),
        }
    }

    /// Construct a source writer using the current config.
    pub fn source<'a, W: ?Sized>(&self, writer: &'a mut W) -> SourceWriter<&'a mut W> {
        SourceWriter {
            upstream: writer,
            tab_width: self.tab_width,
        }
    }
}

/// Writer that replaces tab characters with the configured number of spaces.
pub struct SourceWriter<W> {
    upstream: W,
    tab_width: usize,
}

impl<W: io::Write> io::Write for SourceWriter<W> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        let mut last_term = 0usize;
        for (i, ch) in buf.iter().enumerate() {
            if *ch == b'\t' {
                self.upstream.write_all(&buf[last_term..i])?;
                last_term = i + 1;
                write!(
                    self.upstream,
                    "{space: >width$}",
                    space = "",
                    width = self.tab_width,
                )?;
            }
        }
        self.upstream.write_all(&buf[last_term..])?;
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        self.upstream.flush()
    }
}

/// The display style to use when rendering diagnostics.
#[derive(Clone, Debug)]
pub enum DisplayStyle {
    /// Output a richly formatted diagnostic, with source code previews.
    ///
    /// ```text
    /// error[E0001]: unexpected type in `+` application
    ///   ┌─ test:2:9
    ///   │
    /// 2 │ (+ test "")
    ///   │         ^^ expected `Int` but found `String`
    ///   │
    ///   = expected type `Int`
    ///        found type `String`
    ///
    /// error[E0002]: Bad config found
    ///
    /// ```
    Rich,
    /// Output a short diagnostic, with a line number, severity, and message.
    ///
    /// ```text
    /// test:2:9: error[E0001]: unexpected type in `+` application
    /// error[E0002]: Bad config found
    /// ```
    Short,
}

/// Styles to use when rendering the diagnostic.
#[derive(Clone, Debug)]
pub struct Styles {
    /// The style to use when rendering bug headers.
    /// Defaults to `fg:red bold intense`.
    pub header_bug: ColorSpec,
    /// The style to use when rendering error headers.
    /// Defaults to `fg:red bold intense`.
    pub header_error: ColorSpec,
    /// The style to use when rendering warning headers.
    /// Defaults to `fg:yellow bold intense`.
    pub header_warning: ColorSpec,
    /// The style to use when rendering note headers.
    /// Defaults to `fg:green bold intense`.
    pub header_note: ColorSpec,
    /// The style to use when rendering help headers.
    /// Defaults to `fg:cyan bold intense`.
    pub header_help: ColorSpec,
    /// The style to use when the main diagnostic message.
    /// Defaults to `bold intense`.
    pub header_message: ColorSpec,

    /// The style to use when rendering bug labels.
    /// Defaults to `fg:red`.
    pub primary_label_bug: ColorSpec,
    /// The style to use when rendering error labels.
    /// Defaults to `fg:red`.
    pub primary_label_error: ColorSpec,
    /// The style to use when rendering warning labels.
    /// Defaults to `fg:yellow`.
    pub primary_label_warning: ColorSpec,
    /// The style to use when rendering note labels.
    /// Defaults to `fg:green`.
    pub primary_label_note: ColorSpec,
    /// The style to use when rendering help labels.
    /// Defaults to `fg:cyan`.
    pub primary_label_help: ColorSpec,
    /// The style to use when rendering secondary labels.
    /// Defaults `fg:blue` (or `fg:cyan` on windows).
    pub secondary_label: ColorSpec,

    /// The style to use when rendering the line numbers.
    /// Defaults `fg:blue` (or `fg:cyan` on windows).
    pub line_number: ColorSpec,
    /// The style to use when rendering the source code borders.
    /// Defaults `fg:blue` (or `fg:cyan` on windows).
    pub source_border: ColorSpec,
    /// The style to use when rendering the note bullets.
    /// Defaults `fg:blue` (or `fg:cyan` on windows).
    pub note_bullet: ColorSpec,
}

impl Styles {
    /// The style used to mark a header at a given severity.
    pub fn header(&self, severity: Severity) -> &ColorSpec {
        match severity {
            Severity::Bug => &self.header_bug,
            Severity::Error => &self.header_error,
            Severity::Warning => &self.header_warning,
            Severity::Note => &self.header_note,
            Severity::Help => &self.header_help,
        }
    }

    /// The style used to mark a primary or secondary label at a given severity.
    pub fn label(&self, severity: Severity, label_style: LabelStyle) -> &ColorSpec {
        match (label_style, severity) {
            (LabelStyle::Primary, Severity::Bug) => &self.primary_label_bug,
            (LabelStyle::Primary, Severity::Error) => &self.primary_label_error,
            (LabelStyle::Primary, Severity::Warning) => &self.primary_label_warning,
            (LabelStyle::Primary, Severity::Note) => &self.primary_label_note,
            (LabelStyle::Primary, Severity::Help) => &self.primary_label_help,
            (LabelStyle::Secondary, _) => &self.secondary_label,
        }
    }

    #[doc(hidden)]
    pub fn with_blue(blue: Color) -> Styles {
        let header = ColorSpec::new().set_bold(true).set_intense(true).clone();

        Styles {
            header_bug: header.clone().set_fg(Some(Color::Red)).clone(),
            header_error: header.clone().set_fg(Some(Color::Red)).clone(),
            header_warning: header.clone().set_fg(Some(Color::Yellow)).clone(),
            header_note: header.clone().set_fg(Some(Color::Green)).clone(),
            header_help: header.clone().set_fg(Some(Color::Cyan)).clone(),
            header_message: header,

            primary_label_bug: ColorSpec::new().set_fg(Some(Color::Red)).clone(),
            primary_label_error: ColorSpec::new().set_fg(Some(Color::Red)).clone(),
            primary_label_warning: ColorSpec::new().set_fg(Some(Color::Yellow)).clone(),
            primary_label_note: ColorSpec::new().set_fg(Some(Color::Green)).clone(),
            primary_label_help: ColorSpec::new().set_fg(Some(Color::Cyan)).clone(),
            secondary_label: ColorSpec::new().set_fg(Some(blue)).clone(),

            line_number: ColorSpec::new().set_fg(Some(blue)).clone(),
            source_border: ColorSpec::new().set_fg(Some(blue)).clone(),
            note_bullet: ColorSpec::new().set_fg(Some(blue)).clone(),
        }
    }
}

impl Default for Styles {
    fn default() -> Styles {
        // Blue is really difficult to see on the standard windows command line
        #[cfg(windows)]
        const BLUE: Color = Color::Cyan;
        #[cfg(not(windows))]
        const BLUE: Color = Color::Blue;

        Self::with_blue(BLUE)
    }
}

/// Characters to use when rendering the diagnostic.
#[derive(Clone, Debug)]
pub struct Chars {
    /// The character to use for the top-left border of the source.
    /// Defaults to: `'┌'`.
    pub source_border_top_left: char,
    /// The character to use for the top border of the source.
    /// Defaults to: `'─'`.
    pub source_border_top: char,
    /// The character to use for the left border of the source.
    /// Defaults to: `'│'`.
    pub source_border_left: char,
    /// The character to use for the left border break of the source.
    /// Defaults to: `'·'`.
    pub source_border_left_break: char,

    /// The character to use for the note bullet.
    /// Defaults to: `'='`.
    pub note_bullet: char,

    /// The character to use for marking a single-line primary label.
    /// Defaults to: `'^'`.
    pub single_primary_caret: char,
    /// The character to use for marking a single-line secondary label.
    /// Defaults to: `'-'`.
    pub single_secondary_caret: char,

    /// The character to use for marking the start of a multi-line primary label.
    /// Defaults to: `'^'`.
    pub multi_primary_caret_start: char,
    /// The character to use for marking the end of a multi-line primary label.
    /// Defaults to: `'^'`.
    pub multi_primary_caret_end: char,
    /// The character to use for marking the start of a multi-line secondary label.
    /// Defaults to: `'\''`.
    pub multi_secondary_caret_start: char,
    /// The character to use for marking the end of a multi-line secondary label.
    /// Defaults to: `'\''`.
    pub multi_secondary_caret_end: char,
    /// The character to use for the top-left corner of a multi-line label.
    /// Defaults to: `'╭'`.
    pub multi_top_left: char,
    /// The character to use for the top of a multi-line label.
    /// Defaults to: `'─'`.
    pub multi_top: char,
    /// The character to use for the bottom-left corner of a multi-line label.
    /// Defaults to: `'╰'`.
    pub multi_bottom_left: char,
    /// The character to use when marking the bottom of a multi-line label.
    /// Defaults to: `'─'`.
    pub multi_bottom: char,
    /// The character to use for the left of a multi-line label.
    /// Defaults to: `'│'`.
    pub multi_left: char,

    /// The character to use for the left of a pointer underneath a caret.
    /// Defaults to: `'│'`.
    pub pointer_left: char,
}

impl Default for Chars {
    fn default() -> Chars {
        Chars {
            source_border_top_left: '┌',
            source_border_top: '─',
            source_border_left: '│',
            source_border_left_break: '·',

            note_bullet: '=',

            single_primary_caret: '^',
            single_secondary_caret: '-',

            multi_primary_caret_start: '^',
            multi_primary_caret_end: '^',
            multi_secondary_caret_start: '\'',
            multi_secondary_caret_end: '\'',
            multi_top_left: '╭',
            multi_top: '─',
            multi_bottom_left: '╰',
            multi_bottom: '─',
            multi_left: '│',

            pointer_left: '│',
        }
    }
}