use egui::{text::LayoutJob, Color32};
use egui::widgets::text_edit::TextEditOutput;

use std::hash::{Hash, Hasher};

#[derive(Clone, Debug, PartialEq)]
/// CodeEditor struct which stores settings for highlighting.
pub struct CodeEditor {
    id: String,
    numlines: bool,
    numlines_shift: isize,
    numlines_only_natural: bool,
    fontsize: f32,
    stick_to_bottom: bool,
    desired_width: f32,
}

impl Hash for CodeEditor {
    fn hash<H: Hasher>(&self, state: &mut H) {
        #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
        (self.fontsize as u32).hash(state);
    }
}

impl Default for CodeEditor {
    fn default() -> CodeEditor {
        CodeEditor {
            id: String::from("Code Editor"),
            numlines: true,
            numlines_shift: 0,
            numlines_only_natural: false,
            fontsize: 10.0,
            stick_to_bottom: false,
            desired_width: f32::INFINITY,
        }
    }
}

impl CodeEditor {
    pub fn id_source(self, id_source: impl Into<String>) -> Self {
        CodeEditor {
            id: id_source.into(),
            ..self
        }
    }

    /// Use custom font size
    ///
    /// **Default: 10.0**
    pub fn with_fontsize(self, fontsize: f32) -> Self {
        CodeEditor { fontsize, ..self }
    }

    /// Use UI font size
    pub fn with_ui_fontsize(self, ui: &mut egui::Ui) -> Self {
        CodeEditor {
            fontsize: egui::TextStyle::Monospace.resolve(ui.style()).size,
            ..self
        }
    }

    /// Show or hide lines numbering
    ///
    /// **Default: true**
    pub fn with_numlines(self, numlines: bool) -> Self {
        CodeEditor { numlines, ..self }
    }

    /// Shift lines numbering by this value
    ///
    /// **Default: 0**
    pub fn with_numlines_shift(self, numlines_shift: isize) -> Self {
        CodeEditor {
            numlines_shift,
            ..self
        }
    }

    /// Show lines numbering only above zero, useful for enabling numbering since nth row
    ///
    /// **Default: false**
    pub fn with_numlines_only_natural(self, numlines_only_natural: bool) -> Self {
        CodeEditor {
            numlines_only_natural,
            ..self
        }
    }

    /// Should the containing area shrink if the content is small?
    ///
    /// **Default: false**
    pub fn auto_shrink(self, shrink: bool) -> Self {
        CodeEditor {
            desired_width: if shrink { 0.0 } else { self.desired_width },
            ..self
        }
    }

    /// Sets the desired width of the code editor
    ///
    /// **Default: `f32::INFINITY`**
    pub fn desired_width(self, width: f32) -> Self {
        CodeEditor {
            desired_width: width,
            ..self
        }
    }

    /// Stick to bottom
    /// The scroll handle will stick to the bottom position even while the content size
    /// changes dynamically. This can be useful to simulate terminal UIs or log/info scrollers.
    /// The scroll handle remains stuck until user manually changes position. Once "unstuck"
    /// it will remain focused on whatever content viewport the user left it on. If the scroll
    /// handle is dragged to the bottom it will again become stuck and remain there until manually
    /// pulled from the end position.
    ///
    /// **Default: false**
    pub fn stick_to_bottom(self, stick_to_bottom: bool) -> Self {
        CodeEditor {
            stick_to_bottom,
            ..self
        }
    }

    pub fn format(&self, string: &str) -> egui::text::TextFormat {
        let font_id = egui::FontId::monospace(self.fontsize);
        let color = Color32::WHITE;
        egui::text::TextFormat::simple(font_id, color)
    }

    fn numlines_show(&self, ui: &mut egui::Ui, text: &str) {
        let total = if text.ends_with('\n') || text.is_empty() {
            text.lines().count() + 1
        } else {
            text.lines().count()
        } as isize;

        let max_indent = total.to_string().len().max(
            !self.numlines_only_natural as usize * self.numlines_shift.to_string().len(),
        );
        let mut counter = (1..=total)
            .map(|i| {
                let num = i + self.numlines_shift;
                if num <= 0 && self.numlines_only_natural {
                    String::new()
                } else {
                    let label = num.to_string();
                    format!(
                        "{}{label}",
                        " ".repeat(max_indent.saturating_sub(label.len()))
                    )
                }
            })
            .collect::<Vec<String>>()
            .join("\n");

        #[allow(clippy::cast_precision_loss)]
        let width = max_indent as f32
            * self.fontsize
            * 0.5
            * !(total + self.numlines_shift <= 0 && self.numlines_only_natural) as u8
                as f32;

        let mut layouter = |ui: &egui::Ui, string: &str, _wrap_width: f32| {
            let layout_job = egui::text::LayoutJob::single_section(
                string.to_string(),
                egui::TextFormat::simple(
                    egui::FontId::monospace(self.fontsize),
                    Color32::WHITE,
                ),
            );
            ui.fonts(|f| f.layout_job(layout_job))
        };

        ui.add(
            egui::TextEdit::multiline(&mut counter)
                .id_source(format!("{}_numlines", self.id))
                .font(egui::TextStyle::Monospace)
                .interactive(false)
                .frame(false)
                .desired_width(width)
                .layouter(&mut layouter),
        );
    }

    /// Show Code Editor
    pub fn show(
        &mut self,
        ui: &mut egui::Ui,
        text: &mut dyn egui::TextBuffer,
    ) -> TextEditOutput {
        let mut text_edit_output: Option<TextEditOutput> = None;
        let code_editor = |ui: &mut egui::Ui| {
            ui.horizontal_top(|h| {
                if self.numlines {
                    self.numlines_show(h, text.as_str());
                }
                egui::ScrollArea::horizontal()
                    .hscroll(true)
                    .id_salt(format!("{}_inner_scroll", self.id))
                    .show(h, |ui| {
                        let output = egui::TextEdit::multiline(text)
                            .id_source(&self.id)
                            .lock_focus(true)
                            .frame(false)
                            .desired_width(self.desired_width)
                            .show(ui);
                        text_edit_output = Some(output);
                    });
            });
        };

        egui::ScrollArea::vertical()
            .id_salt(format!("{}_outer_scroll", self.id))
            .stick_to_bottom(self.stick_to_bottom)
            .show(ui, code_editor);

        text_edit_output.expect("TextEditOutput should exist at this point")
    }
}