//! Form field widgets: a labelled row, a number field that keeps what is being typed until it
//! is a number, a drop-down, a text field. They know nothing of FieldCraft (colours and widths
//! come in a [`Style`]), so they can move to the shared Craft UI crate.
//!
//! The row layout (a label column, a long label wrapping inside it, then the field) is
//! adapted from SolidCraft's dialog rows (`crates/ui-egui/src/dialogs.rs`, MIT OR Apache-2.0).

use egui::{Color32, Id, RichText, Ui, vec2};

/// Widths and colours of a form.
#[derive(Clone, Copy, Debug)]
pub struct Style {
    /// The label column.
    pub label_width: f32,
    pub dim: Color32,
    pub error: Color32,
    /// The mark of a required field.
    pub required: Color32,
}

/// Row height.
pub const ROW_H: f32 = 22.0;

/// The room the marks after a label take: the required `*` and the help [`help_mark`].
pub fn marks_width(required: bool, help: bool) -> f32 {
    MARK_GAP + if required { STAR_W } else { 0.0 } + if help { HELP_W } else { 0.0 }
}

/// Between a label and its marks.
const MARK_GAP: f32 = 2.0;
/// The required mark.
const STAR_W: f32 = 9.0;
/// The help mark and the space before it.
const HELP_W: f32 = 13.0;
/// A label longer than its column wraps onto this many lines (labels are short phrases).
pub const LABEL_LINES: usize = 2;

/// The font of a row's label.
pub fn label_font(ui: &Ui) -> egui::FontId {
    egui::TextStyle::Body.resolve(ui.style())
}

/// The width of `label` on one line, with its marks: what a label column needs to show it whole.
pub fn label_width(ui: &Ui, label: &str, required: bool, help: bool) -> f32 {
    crate::elide::width(ui, label, &label_font(ui)).ceil() + marks_width(required, help)
}

/// `label` laid out in a column `wrap` wide, on at most [`LABEL_LINES`] lines (elided past them).
pub fn label_galley(ui: &Ui, label: &str, color: Color32, wrap: f32) -> std::sync::Arc<egui::Galley> {
    let mut job = egui::text::LayoutJob::simple(label.to_string(), label_font(ui), color, wrap.max(0.0));
    job.wrap.max_rows = LABEL_LINES;
    ui.painter().layout_job(job)
}

/// A row: `label` (with a mark when `required`, and [`help_mark`] when there is `help`) in the
/// label column, then `add`. A label wider than the column wraps onto [`LABEL_LINES`] lines; the
/// marks always follow it inside the column. Hovering the label or the mark shows the label and
/// `help`.
pub fn row<R>(ui: &mut Ui, s: &Style, label: &str, required: bool, help: &str, add: impl FnOnce(&mut Ui) -> R) -> R {
    ui.horizontal(|ui| {
        let galley = label_galley(ui, label, s.dim, s.label_width - marks_width(required, !help.is_empty()));
        let (rect, response) = ui.allocate_exact_size(vec2(s.label_width, galley.size().y.max(ROW_H)), egui::Sense::hover());
        let text_rect = egui::Align2::LEFT_CENTER.anchor_size(rect.left_center(), galley.size());
        let tip = if help.is_empty() { label.to_string() } else { format!("{label}\n{help}") };
        response.widget_info(|| egui::WidgetInfo::labeled(egui::WidgetType::Label, true, label));
        response.on_hover_text(&tip);
        // The marks sit after the label's last line.
        let last = galley.rows.last().map_or(egui::Rect::ZERO, |r| r.rect());
        let mark_y = text_rect.top() + last.center().y;
        let mut x = text_rect.left() + last.right() + MARK_GAP;
        ui.painter().galley(text_rect.min, galley, s.dim);
        if required {
            let star = egui::Rect::from_min_size(egui::pos2(x, mark_y - 7.0), vec2(STAR_W, 14.0));
            ui.painter().text(egui::pos2(x, mark_y), egui::Align2::LEFT_CENTER, "*", label_font(ui), s.required);
            ui.interact(star, ui.id().with("required"), egui::Sense::hover()).on_hover_text("Required");
            x += STAR_W;
        }
        if !help.is_empty() {
            let mark = egui::Rect::from_center_size(egui::pos2(x + HELP_W / 2.0, mark_y), vec2(11.0, 11.0));
            paint_help_mark(ui.painter(), mark, s.dim);
            ui.interact(mark, ui.id().with("help"), egui::Sense::hover()).on_hover_text(&tip);
        }
        add(ui)
    })
    .inner
}

/// A small circled "i" after a label that has help, drawn (the UI font has no such glyph).
pub fn paint_help_mark(painter: &egui::Painter, rect: egui::Rect, color: Color32) {
    painter.circle_stroke(rect.center(), 5.0, egui::Stroke::new(1.0, color));
    painter.text(rect.center(), egui::Align2::CENTER_CENTER, "i", egui::FontId::proportional(8.5), color);
}

/// The width of `unit` after a field ([`unit`]), with the space before it; 0 without one.
pub fn unit_width(ui: &Ui, unit: Option<&str>) -> f32 {
    unit.map_or(0.0, |u| crate::elide::width(ui, u, &egui::TextStyle::Small.resolve(ui.style())).ceil() + ui.spacing().item_spacing.x)
}

/// A message under a field, aligned with the fields.
pub fn note(ui: &mut Ui, s: &Style, text: &str, color: Color32) {
    ui.horizontal(|ui| {
        ui.add_space(s.label_width + ui.spacing().item_spacing.x);
        ui.add(egui::Label::new(RichText::new(text).small().color(color)).wrap());
    });
}

/// What a number field did this frame.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum NumberEdit {
    Unchanged,
    /// A new value; `None` when the field was emptied.
    Set(Option<f64>),
    /// What is typed is not a number (yet); the value is unchanged.
    Invalid,
}

/// The typed text of a field and the value it was typed over: kept while the value stays the
/// same, so a half-typed `1e-` survives frames and an outside change (undo, the JSON view)
/// replaces it.
#[derive(Clone, Debug, Default)]
struct Draft {
    text: String,
    over: Option<f64>,
}

/// A number field: shows `value` (or the typed text), greys `hint` when empty, and reports a new
/// value only when the text is a finite number (or empty). `integer` refuses fractions. `id` is the
/// field's own (unique in the form, and differing between forms): it keys both the typed text and
/// the widget, so focus and typing never move to another form's field at the same place.
pub fn number(ui: &mut Ui, s: &Style, id: Id, value: Option<f64>, hint: &str, integer: bool, width: f32) -> NumberEdit {
    let shown = |v: Option<f64>| v.map(format_number).unwrap_or_default();
    let mut draft = ui.data(|d| d.get_temp::<Draft>(id)).filter(|d| d.over == value).unwrap_or_else(|| Draft { text: shown(value), over: value });
    let parse = |t: &str| -> Option<Option<f64>> {
        let t = t.trim();
        if t.is_empty() {
            return Some(None);
        }
        let x = t.parse::<f64>().ok().filter(|x| x.is_finite())?;
        (!integer || x.fract() == 0.0).then_some(Some(x))
    };
    let bad = parse(&draft.text).is_none();
    let mut edit = egui::TextEdit::singleline(&mut draft.text).id(id).desired_width(width).hint_text(RichText::new(hint).italics().color(s.dim));
    if bad {
        edit = edit.text_color(s.error);
    }
    let r = ui.add(edit);
    let out = if r.changed() {
        match parse(&draft.text) {
            Some(v) => {
                draft.over = v;
                NumberEdit::Set(v)
            }
            None => NumberEdit::Invalid,
        }
    } else if bad {
        NumberEdit::Invalid
    } else {
        NumberEdit::Unchanged
    };
    ui.data_mut(|d| d.insert_temp(id, draft));
    out
}

/// A number as typed: integers without a fraction, others in their shortest round-trip form.
pub fn format_number(x: f64) -> String {
    if x.fract() == 0.0 && x.abs() < 1e15 {
        format!("{}", x as i64)
    } else {
        serde_json::Number::from_f64(x).map_or_else(|| x.to_string(), |n| n.to_string())
    }
}

/// A drop-down of `options` (labels); returns the index picked this frame.
pub fn combo(ui: &mut Ui, id: Id, selected: &str, options: &[&str], width: f32) -> Option<usize> {
    let mut picked = None;
    egui::ComboBox::from_id_salt(id).selected_text(selected).width(width).truncate().show_ui(ui, |ui| {
        for (i, o) in options.iter().enumerate() {
            if ui.selectable_label(*o == selected, *o).clicked() {
                picked = Some(i);
            }
        }
    });
    picked
}

/// A one-line text field with a greyed hint, keyed by `id` (see [`number`]); true when it changed.
pub fn text(ui: &mut Ui, s: &Style, id: Id, value: &mut String, hint: &str, width: f32) -> bool {
    ui.add(egui::TextEdit::singleline(value).id(id).desired_width(width).hint_text(RichText::new(hint).italics().color(s.dim))).changed()
}

/// A short label before a field ("X"), dim.
pub fn caption(ui: &mut Ui, s: &Style, text: &str) {
    ui.label(RichText::new(text).small().color(s.dim));
}

/// A unit after a field.
pub fn unit(ui: &mut Ui, s: &Style, unit: Option<&str>) {
    if let Some(u) = unit {
        ui.label(RichText::new(u).small().color(s.dim));
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn numbers_print_as_typed() {
        assert_eq!(format_number(210000.0), "210000");
        assert_eq!(format_number(0.3), "0.3");
        assert_eq!(format_number(7.85e-9), "7.85e-9");
        assert_eq!(format_number(-2.0), "-2");
    }
}