bezel-editor 0.1.8

//! Where a picture comes from.
//!
//! Four ways in, and they differ only in what they have to go on. A pasted URL
//! and the slash menu already name a place to fetch from. A dropped file names
//! one on disk. A pasted screenshot names nothing at all — it is bytes, and
//! bytes have to be put somewhere before a document can point at them, which is
//! the app's decision and not this library's. Hence [`set_image_store`],
//! installed once at boot like `markdown::set_link_preview`.

use std::path::Path;

use gpui::{
    AnyElement, App, Axis, Context, CursorStyle, Entity, ExternalPaths, Focusable as _, Global,
    MouseButton, Point, Window, div, img, prelude::*, px,
};
use markdown::{Block, BlockKind, Cursor, Part, Selection, Text};
use theme::Theme;
use ui::{
    input::TextField,
    popover,
    widgets::{Layout as _, SplitStyle},
};

use crate::{
    comment::Delta,
    editor::{
        Editor, MIN_IMAGE_WIDTH,
        keys::{CancelUrl, ConfirmUrl},
    },
    history::EditKind,
};

/// The key context the URL prompt claims, so `enter` fills the picture in
/// rather than splitting the document behind it.
pub const PROMPT_CONTEXT: &str = "BezelImagePrompt";

/// Wide enough for a URL to be read back before it is confirmed.
const PROMPT_WIDTH: f32 = 280.0;

/// A picture with no address of its own, and what the app is asked about.
pub enum Source<'a> {
    /// Bytes off the clipboard — a screenshot, which has no name anywhere.
    Bytes(&'a gpui::Image),
    /// A file dragged in from outside, which has one until it is moved.
    File(&'a Path),
}

/// The URL to write down for `source`, and `None` for one the app will not
/// keep — a dropped file then stays where it already is, and a screenshot is
/// let go.
pub type ImageStore = fn(Source) -> Option<String>;

struct Installed(ImageStore);

impl Global for Installed {}

/// `editor::set_image_store(cx, my_store)` — call once at boot. Without it a
/// screenshot cannot be pasted at all: there is nowhere to put the bytes, and
/// a document holds a URL.
pub fn set_image_store(cx: &mut App, store: ImageStore) {
    cx.set_global(Installed(store));
}

fn stored(cx: &App, source: Source) -> Option<String> {
    (cx.try_global::<Installed>()?.0)(source)
}

/// An open prompt: the image it will fill, the field being typed into, and
/// where the card hangs.
pub(crate) struct Prompt {
    block: usize,
    field: Entity<TextField>,
    at: Point<gpui::Pixels>,
}

impl Editor {
    /// Ask for the URL of the image at `ix`, and hand it the keys.
    pub(super) fn prompt_for_url(
        &mut self,
        ix: usize,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let Some(bounds) = self.layouts.block_bounds(ix) else {
            return;
        };
        // The context goes on the *field*: gpui resolves a chord to the binding
        // matching deepest in the focus path, and nothing is deeper than the
        // focused field — a container around it cannot win `enter`.
        let field = cx.new(|cx| {
            TextField::new(cx)
                .with_placeholder("Paste an image URL")
                .with_key_context(PROMPT_CONTEXT)
                .with_frame(false)
        });
        window.focus(&field.focus_handle(cx), cx);
        self.slash = None;
        self.url_prompt = Some(Prompt {
            block: ix,
            field,
            at: gpui::point(
                bounds.origin.x - self.origin.x,
                bounds.origin.y - self.origin.y + bounds.size.height,
            ),
        });
        cx.notify();
    }

    /// Take what was typed. An image already carries its caption, and
    /// [`markdown::Doc::set_kind`] carries it across the turn.
    pub(super) fn confirm_url(
        &mut self,
        _: &ConfirmUrl,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let Some(prompt) = self.url_prompt.take() else {
            return;
        };
        let url = prompt.field.read(cx).content().trim().to_string();
        self.focus_handle.clone().focus(window, cx);
        if url.is_empty() {
            return cx.notify();
        }
        self.edit(EditKind::Structure, cx, |this| {
            this.doc.set_kind(
                prompt.block,
                BlockKind::Image {
                    url,
                    alt: Text::default(),
                    width: None,
                },
            );
            this.selection =
                Selection::at(Cursor::new(prompt.block, Part::Caption, 0).clamp(&this.doc));
            vec![]
        });
    }

    pub(super) fn cancel_url(
        &mut self,
        _: &CancelUrl,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        if self.url_prompt.take().is_some() {
            self.focus_handle.clone().focus(window, cx);
            cx.notify();
        }
    }

    /// Files dragged in from outside. The store says where each one belongs,
    /// and a picture it does not want paints from where it already is.
    pub(super) fn drop_paths(&mut self, paths: &ExternalPaths, cx: &mut Context<Self>) {
        let urls: Vec<String> = paths
            .paths()
            .iter()
            .filter(|path| markdown::is_image(&path.to_string_lossy()))
            .map(|path| {
                stored(cx, Source::File(path))
                    .unwrap_or_else(|| path.to_string_lossy().into_owned())
            })
            .collect();
        let ix = self.dropping.take().unwrap_or(self.cursor().block);
        self.place_images(ix, urls, cx);
        cx.notify();
    }

    /// Bytes off the clipboard. `false` when no store is installed, which
    /// leaves the paste to whatever else the clipboard was carrying.
    pub(super) fn paste_image(&mut self, image: &gpui::Image, cx: &mut Context<Self>) -> bool {
        let Some(url) = stored(cx, Source::Bytes(image)) else {
            return false;
        };
        self.place_images(self.cursor().block, vec![url], cx);
        true
    }

    /// Put pictures into the document after block `ix` — or in its place, when
    /// that block is the empty paragraph a caret was left sitting in.
    fn place_images(&mut self, ix: usize, urls: Vec<String>, cx: &mut Context<Self>) {
        if urls.is_empty() {
            return;
        }
        self.edit(EditKind::Structure, cx, |this| {
            let here = this.doc.blocks.get(ix);
            let indent = here.map_or(0, |block| block.indent);
            let empty = here.is_some_and(
                |block| matches!(&block.kind, BlockKind::Paragraph(text) if text.is_empty()),
            );
            let mut deltas = Vec::new();
            let first = if empty {
                this.doc.blocks.remove(ix);
                deltas.push(Delta::Moved {
                    at: ix..ix + 1,
                    to: None,
                });
                ix
            } else {
                (ix + 1).min(this.doc.blocks.len())
            };
            let last = first + urls.len() - 1;
            for (offset, url) in urls.into_iter().enumerate() {
                this.doc.blocks.insert(
                    first + offset,
                    Block::at(
                        BlockKind::Image {
                            url,
                            alt: Text::default(),
                            width: None,
                        },
                        indent,
                    ),
                );
            }
            this.doc.repair();
            this.selection = Selection::at(Cursor::new(last, Part::Caption, 0).clamp(&this.doc));
            deltas.push(Delta::Opened {
                at: first,
                count: last + 1 - first,
            });
            deltas
        });
    }

    /// The click target over an image with no URL yet — the row that says so
    /// is painted by the renderer, and this is what answers a press on it.
    ///
    /// The one under the pointer, else the one the caret is in, which is
    /// [`Editor::language_chip`]'s rule and for the same reason: one element
    /// placed from the recorded frames, rather than one per block.
    pub(super) fn image_target(&self, cx: &mut Context<Self>) -> Option<AnyElement> {
        let blank = |ix: &usize| {
            matches!(
                self.doc.blocks.get(*ix).map(|block| &block.kind),
                Some(BlockKind::Image { url, .. }) if url.is_empty()
            )
        };
        let ix = [self.hovered, Some(self.cursor().block)]
            .into_iter()
            .flatten()
            .find(blank)?;
        let bounds = self.layouts.block_bounds(ix)?;
        Some(
            div()
                .id("image-target")
                .absolute()
                .left(bounds.origin.x - self.origin.x)
                .top(bounds.origin.y - self.origin.y)
                .w(bounds.size.width)
                .h(bounds.size.height)
                .cursor(CursorStyle::PointingHand)
                .on_mouse_down(
                    MouseButton::Left,
                    cx.listener(move |this, _: &gpui::MouseDownEvent, window, cx| {
                        // The editor's own press listener runs after this one
                        // and would take the focus straight back.
                        this.press_claimed = true;
                        this.prompt_for_url(ix, window, cx);
                    }),
                )
                .into_any_element(),
        )
    }

    /// How wide the picture at `ix` is allowed to be: from its own left edge
    /// to the editor's right one, so an indented image gets the narrower
    /// column it actually sits in.
    ///
    /// Never below [`MIN_IMAGE_WIDTH`]: a window narrower than the floor would
    /// otherwise put the ceiling under it, which clamps the wrong way round
    /// and panics rather than giving back a small picture.
    pub(super) fn column_width(&self, ix: usize) -> Option<u32> {
        let bounds = self.layouts.picture_bounds(ix)?;
        let column = self.origin.x + self.width - bounds.origin.x;
        Some(column.max(px(MIN_IMAGE_WIDTH)).as_f32().round() as u32)
    }

    /// The width a drag reaching `x` asks for, bounded by the column.
    pub(super) fn dragged_width(&self, ix: usize, x: gpui::Pixels) -> Option<u32> {
        let bounds = self.layouts.picture_bounds(ix)?;
        let asked = (x - bounds.origin.x)
            .max(px(MIN_IMAGE_WIDTH))
            .as_f32()
            .round() as u32;
        Some(asked.min(self.column_width(ix)?))
    }

    /// Where the picture at `ix` sits at `width`, in this editor's own
    /// coordinates.
    ///
    /// The width is taken from `width` rather than from the box that painted,
    /// which is a frame behind: a handle placed from that box would sit at the
    /// picture's previous edge until something unrelated asked for another
    /// frame. The origin and the height are read back, because neither is
    /// something this can work out and both are right for the picture as it
    /// stands.
    pub(super) fn picture_box(
        &self,
        ix: usize,
        width: Option<u32>,
    ) -> Option<gpui::Bounds<gpui::Pixels>> {
        let painted = self.layouts.picture_bounds(ix)?;
        // Zero until the picture has decoded — nothing to grab yet.
        if painted.size.width <= px(0.0) {
            return None;
        }
        let column = self.column_width(ix)?;
        let width = width.map_or(painted.size.width, |width| px(width.min(column) as f32));
        Some(gpui::Bounds::new(
            gpui::point(
                painted.origin.x - self.origin.x,
                painted.origin.y - self.origin.y,
            ),
            gpui::size(width, painted.size.height),
        ))
    }

    /// End a resize, writing the width down. `false` when none was running,
    /// which is what leaves the release to whatever else claims it.
    pub(super) fn drop_resize(&mut self, window: &mut Window, cx: &mut Context<Self>) -> bool {
        let Some((ix, live)) = self.resizing.take() else {
            return false;
        };
        // Dragged back out to the column: forget the width rather than pin it
        // a pixel short, so letting go all the way round-trips as plain
        // `![alt](url)` again.
        let width = match (live, self.column_width(ix)) {
            (Some(live), Some(full)) if live + 2 >= full => None,
            _ => live,
        };
        let current = self.doc.blocks.get(ix).and_then(|block| match &block.kind {
            BlockKind::Image { width, .. } => Some(*width),
            _ => None,
        });
        if current != Some(width) {
            self.edit(EditKind::Structure, cx, |this| {
                if let Some(BlockKind::Image { width: at, .. }) =
                    this.doc.blocks.get_mut(ix).map(|block| &mut block.kind)
                {
                    *at = width;
                }
                vec![]
            });
            // Handed back its natural width, which only the paint that
            // measures it knows: the next frame still places the handle from
            // the width being left behind, and this asks for the one after,
            // which can see the picture it belongs to.
            if width.is_none() {
                window.refresh();
            }
        } else {
            // The stand-in picture is painted from `resizing` and this frame
            // no longer has one, which an edit would have said for us.
            cx.notify();
        }
        true
    }

    /// The grab strip along a picture's right edge — the one under the
    /// pointer, else the one being resized (which can end up outside the
    /// image once a drag overshoots its bounds).
    ///
    /// Painted with [`ui::widgets::Layout::split_handle`] rather than a
    /// bespoke bar: a pane divider and an image's edge are the same shape,
    /// a hairline in a wider grab strip, so the resized picture matches the
    /// rest of the app's resize affordances instead of inventing a second one.
    pub(super) fn resize_handle(
        &self,
        theme: &Theme,
        cx: &mut Context<Self>,
    ) -> Option<AnyElement> {
        let has_url = |ix: &usize| {
            matches!(
                self.doc.blocks.get(*ix).map(|block| &block.kind),
                Some(BlockKind::Image { url, .. }) if !url.is_empty()
            )
        };
        let ix = [self.resizing.map(|(ix, _)| ix), self.hovered]
            .into_iter()
            .flatten()
            .find(has_url)?;
        let dragging = self.resizing.is_some_and(|(resizing, _)| resizing == ix);
        // The document's own value, so a press that never moves releases into
        // the width it started from and writes nothing.
        let current = match self.doc.blocks.get(ix).map(|block| &block.kind) {
            Some(BlockKind::Image { width, .. }) => *width,
            _ => None,
        };
        let picture = self.picture_box(ix, current)?;
        Some(
            theme
                .split_handle(Axis::Horizontal, SplitStyle::Line { dragging })
                .id("image-resize-handle")
                .absolute()
                .left(picture.origin.x + picture.size.width - px(4.5))
                .top(picture.origin.y)
                .h(picture.size.height)
                .on_mouse_down(
                    MouseButton::Left,
                    cx.listener(move |this, _: &gpui::MouseDownEvent, _, cx| {
                        this.press_claimed = true;
                        this.resizing = Some((ix, current));
                        cx.notify();
                    }),
                )
                .into_any_element(),
        )
    }

    /// The picture at its live width while a resize is in flight — painted a
    /// second time, directly over the real one, because that one is
    /// [`markdown::Doc`] data and the document holds nothing until the handle
    /// is released.
    pub(super) fn resize_preview(&self) -> Option<AnyElement> {
        // Nothing dragged yet, so nothing to stand in for: the picture already
        // painted is the picture this width means.
        let (ix, live) = match self.resizing? {
            (ix, Some(live)) => (ix, live),
            _ => return None,
        };
        let Some(BlockKind::Image { url, .. }) = self.doc.blocks.get(ix).map(|block| &block.kind)
        else {
            return None;
        };
        let box_ = self.picture_box(ix, Some(live))?;
        let picture = match url.contains("://") {
            true => img(gpui::SharedString::from(url.to_string())),
            false => img(std::path::PathBuf::from(url)),
        };
        Some(
            div()
                .absolute()
                .left(box_.origin.x)
                .top(box_.origin.y)
                // No height: the picture derives its own from the width it is
                // given, which is right whatever it is a picture of. Computing
                // one here would need an aspect ratio, and the only box to
                // read one off spans the column rather than the picture until
                // a width has been written down.
                .w(box_.size.width)
                .overflow_hidden()
                .child(picture.w(box_.size.width))
                .into_any_element(),
        )
    }

    /// The prompt itself, under the picture it belongs to.
    pub(super) fn url_prompt(&self, theme: &Theme, cx: &mut Context<Self>) -> Option<AnyElement> {
        let prompt = self.url_prompt.as_ref()?;
        Some(popover::menu_at(
            "image-url",
            prompt.at,
            popover::popover_card(theme)
                .w(px(PROMPT_WIDTH))
                // Without this the editor's own press listener runs next and
                // takes the focus back off the field being clicked into.
                .on_mouse_down(
                    MouseButton::Left,
                    cx.listener(|this, _: &gpui::MouseDownEvent, _, _| this.press_claimed = true),
                )
                .on_mouse_down_out(
                    cx.listener(|this, _, window, cx| this.cancel_url(&CancelUrl, window, cx)),
                )
                // The card is this field's frame; a box on the field would be a
                // second one. Padded like a menu row so the text lands where a
                // row's would.
                .child(
                    div()
                        .px(px(8.0))
                        .py(px(6.0))
                        .child(prompt.field.clone().into_any_element()),
                )
                .into_any_element(),
            None,
        ))
    }
}