// SPDX-License-Identifier: Unlicense OR MIT

package pointer

import (
	"encoding/binary"
	"fmt"
	"image"
	"strings"
	"time"

	"gioui.org/f32"
	"gioui.org/internal/ops"
	"gioui.org/io/event"
	"gioui.org/io/key"
	"gioui.org/op"
)

// Event is a pointer event.
type Event struct {
	Type   Type
	Source Source
	// PointerID is the id for the pointer and can be used
	// to track a particular pointer from Press to
	// Release or Cancel.
	PointerID ID
	// Priority is the priority of the receiving handler
	// for this event.
	Priority Priority
	// Time is when the event was received. The
	// timestamp is relative to an undefined base.
	Time time.Duration
	// Buttons are the set of pressed mouse buttons for this event.
	Buttons Buttons
	// Position is the position of the event, relative to
	// the current transformation, as set by op.TransformOp.
	Position f32.Point
	// Scroll is the scroll amount, if any.
	Scroll f32.Point
	// Modifiers is the set of active modifiers when
	// the mouse button was pressed.
	Modifiers key.Modifiers
}

// PassOp sets the pass-through mode. InputOps added while the pass-through
// mode is set don't block events to siblings.
type PassOp struct {
}

// PassStack represents a PassOp on the pass stack.
type PassStack struct {
	ops     *ops.Ops
	id      ops.StackID
	macroID int
}

// InputOp declares an input handler ready for pointer
// events.
type InputOp struct {
	Tag event.Tag
	// Grab, if set, request that the handler get
	// Grabbed priority.
	Grab bool
	// Types is a bitwise-or of event types to receive.
	Types Type
	// ScrollBounds describe the maximum scrollable distances in both
	// axes. Specifically, any Event e delivered to Tag will satisfy
	//
	// ScrollBounds.Min.X <= e.Scroll.X <= ScrollBounds.Max.X (horizontal axis)
	// ScrollBounds.Min.Y <= e.Scroll.Y <= ScrollBounds.Max.Y (vertical axis)
	ScrollBounds image.Rectangle
}

type ID uint16

// Type of an Event.
type Type uint

// Priority of an Event.
type Priority uint8

// Source of an Event.
type Source uint8

// Buttons is a set of mouse buttons
type Buttons uint8

// Cursor denotes a pre-defined cursor shape. Its Add method adds an
// operation that sets the cursor shape for the current clip area.
type Cursor byte

// The cursors correspond to CSS pointer naming.
const (
	// CursorDefault is the default cursor.
	CursorDefault Cursor = iota
	// CursorNone hides the cursor. To show it again, use any other cursor.
	CursorNone
	// CursorText is for selecting and inserting text.
	CursorText
	// CursorVerticalText is for selecting and inserting vertical text.
	CursorVerticalText
	// CursorPointer is for a link.
	// Usually displayed as a pointing hand.
	CursorPointer
	// CursorCrosshair is for a precise location.
	CursorCrosshair
	// CursorAllScroll is for indicating scrolling in all directions.
	// Usually displayed as arrows to all four directions.
	CursorAllScroll
	// CursorColResize is for vertical resize.
	// Usually displayed as a vertical bar with arrows pointing east and west.
	CursorColResize
	// CursorRowResize is for horizontal resize.
	// Usually displayed as a horizontal bar with arrows pointing north and south.
	CursorRowResize
	// CursorGrab is for content that can be grabbed (dragged to be moved).
	// Usually displayed as an open hand.
	CursorGrab
	// CursorGrabbing is for content that is being grabbed (dragged to be moved).
	// Usually displayed as a closed hand.
	CursorGrabbing
	// CursorNotAllowed is shown when the request action cannot be carried out.
	// Usually displayed as a circle with a line through.
	CursorNotAllowed
	// CursorWait is shown when the program is busy and user cannot interact.
	// Usually displayed as a hourglass or the system equivalent.
	CursorWait
	// CursorProgress is shown when the program is busy, but the user can still interact.
	// Usually displayed as a default cursor with a hourglass.
	CursorProgress
	// CursorNorthWestResize is for top-left corner resizing.
	// Usually displayed as an arrow towards north-west.
	CursorNorthWestResize
	// CursorNorthEastResize is for top-right corner resizing.
	// Usually displayed as an arrow towards north-east.
	CursorNorthEastResize
	// CursorSouthWestResize is for bottom-left corner resizing.
	// Usually displayed as an arrow towards south-west.
	CursorSouthWestResize
	// CursorSouthEastResize is for bottom-right corner resizing.
	// Usually displayed as an arrow towards south-east.
	CursorSouthEastResize
	// CursorNorthSouth is for top-bottom resizing.
	// Usually displayed as a bi-directional arrow towards north-south.
	CursorNorthSouthResize
	// CursorEastWestResize is for left-right resizing.
	// Usually displayed as a bi-directional arrow towards east-west.
	CursorEastWestResize
	// CursorWestResize is for left resizing.
	// Usually displayed as an arrow towards west.
	CursorWestResize
	// CursorEastResize is for right resizing.
	// Usually displayed as an arrow towards east.
	CursorEastResize
	// CursorNorthResize is for top resizing.
	// Usually displayed as an arrow towards north.
	CursorNorthResize
	// CursorSouthResize is for bottom resizing.
	// Usually displayed as an arrow towards south.
	CursorSouthResize
	// CursorNorthEastSouthWestResize is for top-right to bottom-left diagonal resizing.
	// Usually displayed as a double ended arrow on the corresponding diagonal.
	CursorNorthEastSouthWestResize
	// CursorNorthWestSouthEastResize is for top-left to bottom-right diagonal resizing.
	// Usually displayed as a double ended arrow on the corresponding diagonal.
	CursorNorthWestSouthEastResize
)

const (
	// A Cancel event is generated when the current gesture is
	// interrupted by other handlers or the system.
	Cancel Type = (1 << iota) >> 1
	// Press of a pointer.
	Press
	// Release of a pointer.
	Release
	// Move of a pointer.
	Move
	// Drag of a pointer.
	Drag
	// Pointer enters an area watching for pointer input
	Enter
	// Pointer leaves an area watching for pointer input
	Leave
	// Scroll of a pointer.
	Scroll
)

const (
	// Mouse generated event.
	Mouse Source = iota
	// Touch generated event.
	Touch
)

const (
	// Shared priority is for handlers that
	// are part of a matching set larger than 1.
	Shared Priority = iota
	// Foremost priority is like Shared, but the
	// handler is the foremost of the matching set.
	Foremost
	// Grabbed is used for matching sets of size 1.
	Grabbed
)

const (
	// ButtonPrimary is the primary button, usually the left button for a
	// right-handed user.
	ButtonPrimary Buttons = 1 << iota
	// ButtonSecondary is the secondary button, usually the right button for a
	// right-handed user.
	ButtonSecondary
	// ButtonTertiary is the tertiary button, usually the middle button.
	ButtonTertiary
)

// Push the current pass mode to the pass stack and set the pass mode.
func (p PassOp) Push(o *op.Ops) PassStack {
	id, mid := ops.PushOp(&o.Internal, ops.PassStack)
	data := ops.Write(&o.Internal, ops.TypePassLen)
	data[0] = byte(ops.TypePass)
	return PassStack{ops: &o.Internal, id: id, macroID: mid}
}

func (p PassStack) Pop() {
	ops.PopOp(p.ops, ops.PassStack, p.id, p.macroID)
	data := ops.Write(p.ops, ops.TypePopPassLen)
	data[0] = byte(ops.TypePopPass)
}

func (op Cursor) Add(o *op.Ops) {
	data := ops.Write(&o.Internal, ops.TypeCursorLen)
	data[0] = byte(ops.TypeCursor)
	data[1] = byte(op)
}

// Add panics if the scroll range does not contain zero.
func (op InputOp) Add(o *op.Ops) {
	if op.Tag == nil {
		panic("Tag must be non-nil")
	}
	if b := op.ScrollBounds; b.Min.X > 0 || b.Max.X < 0 || b.Min.Y > 0 || b.Max.Y < 0 {
		panic(fmt.Errorf("invalid scroll range value %v", b))
	}
	if op.Types>>16 > 0 {
		panic(fmt.Errorf("value in Types overflows uint16"))
	}
	data := ops.Write1(&o.Internal, ops.TypePointerInputLen, op.Tag)
	data[0] = byte(ops.TypePointerInput)
	if op.Grab {
		data[1] = 1
	}
	bo := binary.LittleEndian
	bo.PutUint16(data[2:], uint16(op.Types))
	bo.PutUint32(data[4:], uint32(op.ScrollBounds.Min.X))
	bo.PutUint32(data[8:], uint32(op.ScrollBounds.Min.Y))
	bo.PutUint32(data[12:], uint32(op.ScrollBounds.Max.X))
	bo.PutUint32(data[16:], uint32(op.ScrollBounds.Max.Y))
}

func (t Type) String() string {
	if t == Cancel {
		return "Cancel"
	}
	var buf strings.Builder
	for tt := Type(1); tt > 0; tt <<= 1 {
		if t&tt > 0 {
			if buf.Len() > 0 {
				buf.WriteByte('|')
			}
			buf.WriteString((t & tt).string())
		}
	}
	return buf.String()
}

func (t Type) string() string {
	switch t {
	case Press:
		return "Press"
	case Release:
		return "Release"
	case Cancel:
		return "Cancel"
	case Move:
		return "Move"
	case Drag:
		return "Drag"
	case Enter:
		return "Enter"
	case Leave:
		return "Leave"
	case Scroll:
		return "Scroll"
	default:
		panic("unknown Type")
	}
}

func (p Priority) String() string {
	switch p {
	case Shared:
		return "Shared"
	case Foremost:
		return "Foremost"
	case Grabbed:
		return "Grabbed"
	default:
		panic("unknown priority")
	}
}

func (s Source) String() string {
	switch s {
	case Mouse:
		return "Mouse"
	case Touch:
		return "Touch"
	default:
		panic("unknown source")
	}
}

// Contain reports whether the set b contains
// all of the buttons.
func (b Buttons) Contain(buttons Buttons) bool {
	return b&buttons == buttons
}

func (b Buttons) String() string {
	var strs []string
	if b.Contain(ButtonPrimary) {
		strs = append(strs, "ButtonPrimary")
	}
	if b.Contain(ButtonSecondary) {
		strs = append(strs, "ButtonSecondary")
	}
	if b.Contain(ButtonTertiary) {
		strs = append(strs, "ButtonTertiary")
	}
	return strings.Join(strs, "|")
}

func (c Cursor) String() string {
	switch c {
	case CursorDefault:
		return "Default"
	case CursorNone:
		return "None"
	case CursorText:
		return "Text"
	case CursorVerticalText:
		return "VerticalText"
	case CursorPointer:
		return "Pointer"
	case CursorCrosshair:
		return "Crosshair"
	case CursorAllScroll:
		return "AllScroll"
	case CursorColResize:
		return "ColResize"
	case CursorRowResize:
		return "RowResize"
	case CursorGrab:
		return "Grab"
	case CursorGrabbing:
		return "Grabbing"
	case CursorNotAllowed:
		return "NotAllowed"
	case CursorWait:
		return "Wait"
	case CursorProgress:
		return "Progress"
	case CursorNorthWestResize:
		return "NorthWestResize"
	case CursorNorthEastResize:
		return "NorthEastResize"
	case CursorSouthWestResize:
		return "SouthWestResize"
	case CursorSouthEastResize:
		return "SouthEastResize"
	case CursorNorthSouthResize:
		return "NorthSouthResize"
	case CursorEastWestResize:
		return "EastWestResize"
	case CursorWestResize:
		return "WestResize"
	case CursorEastResize:
		return "EastResize"
	case CursorNorthResize:
		return "NorthResize"
	case CursorSouthResize:
		return "SouthResize"
	case CursorNorthEastSouthWestResize:
		return "NorthEastSouthWestResize"
	case CursorNorthWestSouthEastResize:
		return "NorthWestSouthEastResize"
	default:
		panic("unknown Type")
	}
}

func (Event) ImplementsEvent() {}