zero/internal/tui/hover.go

package tui

import tea "charm.land/bubbletea/v2"

// hoverKind discriminates which clickable surface a hoverTarget refers to.
type hoverKind int

const (
	hoverNone hoverKind = iota
	// hoverTranscript: a specialist card or collapse/expand toggle header in the
	// main transcript body (or the subchat child view), identified by bodyY.
	hoverTranscript
	// hoverSidebarAgent: a clickable AGENTS sidebar row, identified by sessionID.
	hoverSidebarAgent
	// hoverPlanStep: a plan step row in the sidebar's PLAN section, identified by
	// step index.
	hoverPlanStep
)

// hoverTarget identifies the single clickable row (if any) currently under the
// mouse cursor with no button pressed. Exactly one of bodyY/sessionID/stepIndex is
// meaningful, discriminated by kind.
//
// The sidebar fields deliberately store a STABLE IDENTITY (sessionID, stepIndex),
// not a raw line offset: the AGENTS/PLAN section sizes can change between when a
// hover is detected and when the sidebar next renders (a swarm member's linger
// window elapsing, a plan step completing) with no mouse motion in between to
// re-resolve it. A cached raw offset would then silently point at whatever
// unrelated row now occupies that slot. hoveredSidebarLineOffset (sidebar.go)
// re-resolves the CURRENT line offset for this identity fresh on every render, so
// a row that's gone simply doesn't highlight rather than a wrong one lighting up.
type hoverTarget struct {
	kind      hoverKind
	bodyY     int    // hoverTranscript
	sessionID string // hoverSidebarAgent
	stepIndex int    // hoverPlanStep
}

// mouseHover reports whether msg is a plain cursor-movement event with NO button
// pressed — a hover, not a drag. Requires AllMotion mouse reporting (see View's
// wantsMouseCapture branch); CellMotion only reports motion while a button is held,
// so this predicate would never match under the old mouse mode.
func mouseHover(msg tea.MouseMsg) bool {
	if _, ok := msg.(tea.MouseMotionMsg); !ok {
		return false
	}
	return mouseEvent(msg).Button == tea.MouseNone
}

// updateHoverTarget resolves what's under the cursor for a hover motion, using
// the SAME hit-testers and priority order as the click handlers in
// handleTranscriptSelectionMouse's press case: a sidebar row (agent, then plan
// step) takes priority since it's outside the chat column, then a clickable
// transcript line. Clears the hover when nothing clickable is under the cursor.
func (m model) updateHoverTarget(msg tea.MouseMsg) model {
	if hit, ok := m.sidebarLineAtMouse(msg); ok {
		return m.withHover(hoverTarget{kind: hoverSidebarAgent, sessionID: hit.sessionID})
	}
	if stepIndex, ok := m.planStepAtMouse(msg); ok {
		return m.withHover(hoverTarget{kind: hoverPlanStep, stepIndex: stepIndex})
	}
	if line, ok := m.transcriptLineAtMouse(msg); ok {
		// A permission option reuses its OWN existing keyboard-cursor highlight
		// (see hoverPermissionOption) rather than the m.hover mechanism, so there's
		// nothing further to set here.
		if line.permOption {
			return m.hoverPermissionOption(line.permChoice).withHover(hoverTarget{})
		}
		// Only a card or a collapse/expand toggle header is "clickable" here; plain
		// selectable text (e.g. a user/assistant message) isn't, so hovering over
		// it must not light up as if it were.
		if line.specialistCard || line.toggle {
			return m.withHover(hoverTarget{kind: hoverTranscript, bodyY: line.bodyY})
		}
	}
	return m.withHover(hoverTarget{})
}

// hoverPermissionOption moves the pending permission prompt's cursor to the
// hovered option, reusing its EXISTING keyboard-navigation highlight (the same
// one Tab/Shift+Tab/arrow keys move) instead of new styling — the popup already
// renders whichever option .cursor points at differently. A no-op when no
// permission prompt is pending or the choice isn't found (defensive; every
// permOption line's choice always comes from permissionOptions(request) in the
// first place).
func (m model) hoverPermissionOption(choice permissionDecision) model {
	if m.pendingPermission == nil {
		return m
	}
	for index, option := range permissionOptions(m.pendingPermission.request) {
		if option.choice == choice {
			m.pendingPermission.cursor = index
			return m
		}
	}
	return m
}

func (m model) withHover(t hoverTarget) model {
	m.hover = t
	return m
}

// clearHover drops any hover highlight. Called wherever the underlying content a
// hover target refers to may no longer mean the same thing on the next render — a
// wheel-scroll (the cursor's mapping to a bodyY is only recomputed on the NEXT
// motion event; without clearing, a stale bodyY could coincidentally match a
// DIFFERENT row after the viewport shifts, highlighting the wrong thing) or a
// subchat toggle (bodyY numbering is entirely different between the parent
// transcript and a child session).
func (m model) clearHover() model {
	if m.hover.kind == hoverNone {
		return m
	}
	m.hover = hoverTarget{}
	return m
}