//! Hosting the active tool: pointer/key events → actions → commands.

use serde_json::{Map, Value};
use vectorcraft_geom::Point;
use vectorcraft_tools::distort::perspective::widget::WidgetPlace;
use vectorcraft_tools::{Action, Cursor, Mods, Overlay, PointerEvent, PointerKind, Tool, ToolContext, ToolKey, settings};

use crate::{EngineError, Prefs, Result, Session};

/// View state the tools need from the frontend.
#[derive(Clone, Copy, Debug)]
pub struct ViewInfo {
    pub zoom: f64,
    pub outline: bool,
    pub smart_guides: bool,
    pub snap_to_grid: bool,
    pub show_bbox: bool,
    /// View → Snap to Pixel: drawing and moving land on whole pixels (points at 72 ppi).
    pub snap_to_pixel: bool,
    /// View → Snap to Point: picked points (a transform's reference point) land on anchors.
    pub snap_to_point: bool,
    /// View → Show Corner Widget.
    pub corner_widgets: bool,
    /// The document window (none headless): screen-fixed widgets sit in it.
    pub screen: Option<vectorcraft_tools::ScreenFrame>,
}

impl Default for ViewInfo {
    fn default() -> Self {
        Self {
            zoom: 1.0,
            outline: false,
            smart_guides: true,
            snap_to_grid: false,
            show_bbox: true,
            snap_to_pixel: false,
            snap_to_point: true,
            corner_widgets: true,
            screen: None,
        }
    }
}

/// Requests from tools that only the frontend can fulfil.
#[derive(Clone, Debug, PartialEq)]
pub enum UiRequest {
    Dialog(String, Value),
    SwitchTool(String),
    /// A message for the status bar: the `warning` of a command the tool ran (Liquify skipping
    /// type under the brush).
    Status(String),
}

impl Session {
    pub fn tool_id(&self) -> &'static str {
        self.tool.id()
    }

    /// Switch tools (finishing any pending tool work first).
    pub fn select_tool(&mut self, id: &str, view: ViewInfo) -> Result<()> {
        if self.tool.id() == id {
            return Ok(());
        }
        let acts = self.with_tool_cx(view, |t, cx| t.deactivate(cx));
        self.apply_actions(acts)?;
        self.keep_tool_settings();
        self.tool = self.make_tool(id);
        Ok(())
    }

    /// A fresh `id` tool with the options it keeps ([`settings`]): its last values, from this
    /// session or a saved one.
    pub(crate) fn make_tool(&self, id: &str) -> Box<dyn Tool> {
        let mut t = vectorcraft_tools::create(id);
        Self::restore_tool_settings(&self.prefs, t.as_mut());
        t
    }

    /// Give `t` the persistent options stored for it in `prefs`.
    fn restore_tool_settings(prefs: &Prefs, t: &mut dyn Tool) {
        for (store, keys) in settings::stores(t.id()) {
            let Some(saved) = prefs.tool_settings.get(store) else { continue };
            for k in keys {
                if let Some(v) = saved.get(*k) {
                    t.set_option(k, v);
                }
            }
        }
    }

    /// Store the persistent options of `t` in `prefs` (so they are saved with them too).
    fn store_tool_settings(prefs: &mut Prefs, t: &dyn Tool) {
        let opts = t.options();
        for (store, keys) in settings::stores(t.id()) {
            let saved = prefs.tool_settings.entry(store.to_string()).or_default();
            for k in keys {
                if let Some(v) = opts.get(*k) {
                    saved.insert(k.to_string(), v.clone());
                }
            }
        }
    }

    /// Keep the active tool's persistent options for the next time it, or a tool sharing them, is
    /// made.
    pub(crate) fn keep_tool_settings(&mut self) {
        Self::store_tool_settings(&mut self.prefs, self.tool.as_ref());
    }

    pub(crate) fn with_tool_cx<R>(&mut self, view: ViewInfo, f: impl FnOnce(&mut dyn vectorcraft_tools::Tool, &ToolContext) -> R) -> R
    where
        R: Default,
    {
        let Some(st) = self.active.and_then(|i| self.docs.get(i)) else { return R::default() };
        let (unit, stroke_unit) = (self.general_unit(), self.stroke_unit());
        let cx = ToolContext {
            doc: &st.doc,
            selection: &st.selection,
            zoom: view.zoom,
            isolation: st.isolation,
            paint: &self.paint,
            outline: view.outline,
            smart_guides: view.smart_guides,
            snap_to_grid: view.snap_to_grid,
            show_bbox: view.show_bbox,
            snap_to_pixel: view.snap_to_pixel,
            snap_to_point: view.snap_to_point,
            corner_widgets: view.corner_widgets,
            fill_active: self.fill_active,
            gradient_stop: self.selected_stop(),
            appearance_item: self.appearance_item(),
            constrain_angle: self.prefs.constrain_angle,
            freeform_point: self.selected_freeform_point(),
            raster_sample: self.prefs.eyedropper.sample_size,
            preview_bounds: self.prefs.use_preview_bounds,
            unit,
            stroke_unit,
            paste_plain_text: self.prefs.paste_text_formatting == "plain",
            slices_hidden: self.menu.slices_hidden,
            slices_locked: self.menu.slices_locked,
            screen: view.screen,
            plane_widget: self.prefs.perspective_widget.show.then_some(self.prefs.perspective_widget.position),
        };
        let tool = &mut self.tool;
        match crate::guard::catch_panic(|| f(tool.as_mut(), &cx)) {
            Ok(r) => r,
            Err(msg) => {
                // A bug in the tool: start it afresh and drop its half-done drag.
                let id = self.tool.id();
                self.tool = self.make_tool(id);
                let _ = self.cancel_interaction();
                self.tool_panic = Some(EngineError::Internal { cmd: format!("tool `{id}`"), msg });
                R::default()
            }
        }
    }

    /// The error of a tool that panicked in the last [`Self::with_tool_cx`] call, if any.
    fn take_tool_panic(&mut self) -> Result<()> {
        self.tool_panic.take().map_or(Ok(()), Err)
    }

    /// Feed a pointer event to the active tool. Returns requests for the UI.
    pub fn pointer(&mut self, ev: &PointerEvent, view: ViewInfo) -> Result<Vec<UiRequest>> {
        self.last_view = view;
        // The Plane Switching Widget takes its clicks whatever the tool.
        if let Some(r) = self.plane_widget_pointer(ev, view) {
            return r;
        }
        let acts = self.with_tool_cx(view, |t, cx| t.pointer(cx, ev));
        self.take_tool_panic()?;
        // A gesture may change options (Alt-drag sizes a Liquify brush): keep them.
        if ev.kind == PointerKind::Up {
            self.keep_tool_settings();
        }
        self.apply_actions(acts)
    }

    /// Time passed while the pointer button is held (`dt` seconds; see [`Tool::tick`]): the
    /// desktop app ticks every frame of a press, agents with `holdMs` on a pointer event.
    pub fn tool_tick(&mut self, dt: f64, view: ViewInfo) -> Result<Vec<UiRequest>> {
        if !self.tool.wants_ticks() {
            return Ok(vec![]);
        }
        let acts = self.with_tool_cx(view, |t, cx| t.tick(cx, dt));
        self.take_tool_panic()?;
        self.apply_actions(acts)
    }

    /// Does the active tool want [`Session::tool_tick`]s now?
    pub fn tool_wants_ticks(&self) -> bool {
        self.tool.wants_ticks()
    }

    pub fn tool_key(&mut self, key: ToolKey, mods: Mods, view: ViewInfo) -> Result<Vec<UiRequest>> {
        // 1–4 pick the active perspective plane while the grid is shown.
        if let Some(plane) = self.plane_key(key) {
            self.execute("perspective.plane.set", &serde_json::json!({ "plane": plane.id() }))?;
            return Ok(vec![]);
        }
        let acts = self.with_tool_cx(view, |t, cx| t.key(cx, key, mods));
        self.take_tool_panic()?;
        self.apply_actions(acts)
    }

    /// Typed text for the active tool (Type tool).
    pub fn tool_text(&mut self, text: &str, view: ViewInfo) -> Result<Vec<UiRequest>> {
        let acts = self.with_tool_cx(view, |t, cx| t.text_input(cx, text));
        self.take_tool_panic()?;
        self.apply_actions(acts)
    }

    pub fn tool_wants_text(&self) -> bool {
        self.tool.wants_text()
    }

    /// IME marked text for the active tool (see `Tool::ime_preedit`; `active_chars` counts
    /// characters).
    pub fn tool_preedit(&mut self, text: &str, active_chars: Option<std::ops::Range<usize>>, view: ViewInfo) -> Result<Vec<UiRequest>> {
        let acts = self.with_tool_cx(view, |t, cx| t.ime_preedit(cx, text, active_chars));
        self.take_tool_panic()?;
        self.apply_actions(acts)
    }

    /// Is the active tool showing uncommitted IME text?
    pub fn tool_composing(&self) -> bool {
        self.tool.composing()
    }

    /// The caret line (document space) the IME candidate window follows.
    pub fn tool_ime_caret(&mut self, view: ViewInfo) -> Option<(Point, Point)> {
        self.with_tool_cx(view, |t, cx| t.ime_caret(cx))
    }

    pub fn tool_busy(&self) -> bool {
        self.tool.busy()
    }

    /// Does the active tool take `key` ahead of the shortcuts bound to it (see `Tool::claims_key`)?
    pub fn tool_claims_key(&mut self, key: ToolKey, view: ViewInfo) -> bool {
        self.plane_key(key).is_some() || self.with_tool_cx(view, |t, cx| t.claims_key(cx, key))
    }

    pub fn overlays(&mut self, view: ViewInfo) -> Vec<Overlay> {
        let mut v = self.with_tool_cx(view, |t, cx| t.overlays(cx));
        if let Some(d) = self.active() {
            let w = self.prefs.perspective_widget;
            let place = w.show.then_some(WidgetPlace { screen: view.screen.as_ref(), corner: w.position });
            v.splice(0..0, vectorcraft_tools::distort::perspective::grid_overlays_in(&d.doc, 1.0 / view.zoom.max(1e-9), self.tool.id(), place));
        }
        v
    }

    pub fn cursor(&mut self, p: Point, mods: Mods, view: ViewInfo) -> Cursor {
        self.with_tool_cx(view, |t, cx| t.cursor(cx, p, mods))
    }

    pub fn tool_options(&self) -> Value {
        self.tool.options()
    }
    pub fn set_tool_option(&mut self, key: &str, v: &Value) {
        self.tool.set_option(key, v);
        self.keep_tool_settings();
    }

    /// The options of tool `id`: the active tool's, or those it would have if chosen now.
    pub fn tool_options_of(&self, id: &str) -> Value {
        if id == self.tool.id() { self.tool.options() } else { self.make_tool(id).options() }
    }

    /// Set options of tool `id` (default: the active tool). Another tool's persistent options are
    /// stored for when it is chosen, and the active tool takes those it shares with it (the
    /// Liquify tools' Global Brush Dimensions). Returns the tool's options.
    pub fn set_tool_options(&mut self, id: Option<&str>, values: &Map<String, Value>) -> Value {
        let active = id.is_none_or(|id| id == self.tool.id());
        let mut other = (!active).then(|| self.make_tool(id.unwrap_or_default()));
        let t = other.as_deref_mut().unwrap_or(self.tool.as_mut());
        for (k, v) in values {
            t.set_option(k, v);
        }
        Self::store_tool_settings(&mut self.prefs, t);
        let out = t.options();
        if other.is_some() {
            Self::restore_tool_settings(&self.prefs, self.tool.as_mut());
        }
        out
    }

    /// `tool.setOption {tool?, key?, value?, values?}` (a command of the desktop app and of the
    /// headless host): set one option (`key`, `value`) or several (`values`) of `tool` (default:
    /// the active tool) → its options.
    pub fn set_tool_option_cmd(&mut self, p: &Value) -> std::result::Result<Value, String> {
        let tool = p.get("tool").and_then(Value::as_str);
        if let Some(t) = tool
            && vectorcraft_tools::tool_info(t).is_none()
        {
            return Err(format!("unknown tool `{t}`"));
        }
        let mut values = p.get("values").and_then(Value::as_object).cloned().unwrap_or_default();
        if let Some(k) = p.get("key").and_then(Value::as_str) {
            values.insert(k.to_string(), p.get("value").cloned().unwrap_or(Value::Null));
        }
        Ok(self.set_tool_options(tool, &values))
    }

    /// Let the active tool finish work a command from outside it ended ([`vectorcraft_tools::Tool::after_command`]):
    /// the Type tool stops editing text that is no longer selected. Only while it edits text.
    pub(crate) fn after_command(&mut self) {
        if self.in_tool_actions || !self.tool.wants_text() {
            return;
        }
        let acts = self.with_tool_cx(self.last_view, |t, cx| t.after_command(cx));
        // The command itself succeeded: a failure here only leaves the edit as it was.
        if let Err(e) = self.apply_actions(acts) {
            log::warn!("ending the text edit: {e}");
        }
    }

    /// Apply tool actions. Errors from previews are reported but keep the interaction alive.
    pub fn apply_actions(&mut self, acts: Vec<Action>) -> Result<Vec<UiRequest>> {
        let outer = std::mem::replace(&mut self.in_tool_actions, true);
        let r = self.apply_tool_actions(acts);
        self.in_tool_actions = outer;
        r
    }

    fn apply_tool_actions(&mut self, acts: Vec<Action>) -> Result<Vec<UiRequest>> {
        let mut ui = vec![];
        for a in acts {
            match a {
                Action::Begin(label) => self.begin_interaction(&label)?,
                Action::Preview(cmd, p) => match self.preview(&cmd, &p) {
                    Ok(v) => {
                        if let Some(w) = v.get("warning").and_then(Value::as_str)
                            && !ui.iter().any(|r| matches!(r, UiRequest::Status(s) if s == w))
                        {
                            ui.push(UiRequest::Status(w.to_string()));
                        }
                    }
                    Err(e) => log::warn!("preview {cmd}: {e}"),
                },
                // The drag is over: the dabs of a Liquify stroke have no further use.
                Action::Commit => {
                    self.liquify_stroke = None;
                    self.commit_interaction()?
                }
                Action::Cancel => {
                    self.liquify_stroke = None;
                    self.cancel_interaction()?
                }
                Action::Exec(cmd, p) => {
                    self.execute(&cmd, &p)?;
                }
                Action::Dialog(k, p) => ui.push(UiRequest::Dialog(k, p)),
                Action::SwitchTool(t) => ui.push(UiRequest::SwitchTool(t)),
                Action::Notify(what) => {
                    let view = self.last_view;
                    self.with_tool_cx(view, |t, cx| t.notify(cx, &what));
                }
            }
        }
        Ok(ui)
    }
}