//go:build windows

package main

import (
	"unsafe"

	"github.com/jchv/go-webview2"
	"golang.org/x/sys/windows"
)

// DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 = (DPI_AWARENESS_CONTEXT)-4
const dpiAwarenessContextPerMonitorAwareV2 = ^uintptr(3)

const (
	spiGetWorkArea          = 0x0030
	monitorDefaultToNearest = 2
)

type monitorInfo struct {
	CbSize    uint32
	RcMonitor windows.Rect
	RcWork    windows.Rect
	DwFlags   uint32
}

// enableProcessDPIAware opts into per-monitor DPI before any HWND is created.
// The embedded app.manifest already declares PerMonitorV2; this is a belt-and-
// suspenders call for builds that lose the manifest resource.
func enableProcessDPIAware() {
	user32 := windows.NewLazySystemDLL("user32.dll")
	if p := user32.NewProc("SetProcessDpiAwarenessContext"); p.Find() == nil {
		_, _, _ = p.Call(dpiAwarenessContextPerMonitorAwareV2)
		return
	}
	if p := user32.NewProc("SetProcessDPIAware"); p.Find() == nil {
		_, _, _ = p.Call()
	}
}

func systemDPI() int {
	user32 := windows.NewLazySystemDLL("user32.dll")
	if p := user32.NewProc("GetDpiForSystem"); p.Find() == nil {
		if r, _, _ := p.Call(); r >= 72 && r <= 480 {
			return int(r)
		}
	}
	return 96
}

func windowDPI(hwnd uintptr) int {
	if hwnd != 0 {
		user32 := windows.NewLazySystemDLL("user32.dll")
		if p := user32.NewProc("GetDpiForWindow"); p.Find() == nil {
			if r, _, _ := p.Call(hwnd); r >= 72 && r <= 480 {
				return int(r)
			}
		}
	}
	return systemDPI()
}

func dipsToPhysical(dips, dpi int) int {
	if dpi <= 0 {
		dpi = 96
	}
	return (dips*dpi + 48) / 96
}

func physicalToDIPs(px, dpi int) int {
	if dpi <= 0 {
		dpi = 96
	}
	return (px*96 + dpi/2) / dpi
}

func primaryWorkAreaPhysical() (w, h int, ok bool) {
	var r windows.Rect
	user32 := windows.NewLazySystemDLL("user32.dll")
	p := user32.NewProc("SystemParametersInfoW")
	ret, _, _ := p.Call(spiGetWorkArea, 0, uintptr(unsafe.Pointer(&r)), 0)
	if ret == 0 {
		return 0, 0, false
	}
	return int(r.Right - r.Left), int(r.Bottom - r.Top), true
}

func monitorWorkAreaPhysical(hwnd uintptr) (w, h int, ok bool) {
	if hwnd == 0 {
		return primaryWorkAreaPhysical()
	}
	user32 := windows.NewLazySystemDLL("user32.dll")
	fromWin := user32.NewProc("MonitorFromWindow")
	getInfo := user32.NewProc("GetMonitorInfoW")
	if fromWin.Find() != nil || getInfo.Find() != nil {
		return primaryWorkAreaPhysical()
	}
	hmon, _, _ := fromWin.Call(hwnd, monitorDefaultToNearest)
	if hmon == 0 {
		return primaryWorkAreaPhysical()
	}
	var mi monitorInfo
	mi.CbSize = uint32(unsafe.Sizeof(mi))
	ret, _, _ := getInfo.Call(hmon, uintptr(unsafe.Pointer(&mi)))
	if ret == 0 {
		return primaryWorkAreaPhysical()
	}
	return int(mi.RcWork.Right - mi.RcWork.Left), int(mi.RcWork.Bottom - mi.RcWork.Top), true
}

// computeClientSizeDIPs picks a comfortable client size in DIPs from the
// monitor work area (also expressed as physical px + dpi).
// Target: ~min(1100, workW*0.72) x min(780, workH*0.78), floored near
// 960x680 when the screen allows, always capped with margins.
func computeClientSizeDIPs(workWPhys, workHPhys, dpi int) (w, h int) {
	if dpi <= 0 {
		dpi = 96
	}
	workW := physicalToDIPs(workWPhys, dpi)
	workH := physicalToDIPs(workHPhys, dpi)
	if workW < 320 {
		workW = 320
	}
	if workH < 240 {
		workH = 240
	}

	const marginX, marginY = 64, 64
	maxW := workW - marginX
	maxH := workH - marginY
	if maxW < 480 {
		maxW = workW
	}
	if maxH < 360 {
		maxH = workH
	}
	if maxW < 480 {
		maxW = 480
	}
	if maxH < 360 {
		maxH = 360
	}

	prefW := int(float64(workW) * 0.72)
	if prefW > 1100 {
		prefW = 1100
	}
	prefH := int(float64(workH) * 0.78)
	if prefH > 780 {
		prefH = 780
	}

	if prefW < 960 && maxW >= 960 {
		prefW = 960
	}
	if prefH < 680 && maxH >= 680 {
		prefH = 680
	}

	if prefW > maxW {
		prefW = maxW
	}
	if prefH > maxH {
		prefH = maxH
	}
	if prefW < 640 && maxW >= 640 {
		prefW = 640
	}
	if prefH < 480 && maxH >= 480 {
		prefH = 480
	}
	return prefW, prefH
}

// initialWindowPhysicalSize estimates CreateWindow size before an HWND exists
// (primary work area + system DPI). go-webview2 treats Width/Height as physical
// pixels when the process is DPI-aware.
func initialWindowPhysicalSize() (w, h int) {
	dpi := systemDPI()
	ww, wh, ok := primaryWorkAreaPhysical()
	if !ok || ww <= 0 || wh <= 0 {
		return dipsToPhysical(960, dpi), dipsToPhysical(680, dpi)
	}
	dipW, dipH := computeClientSizeDIPs(ww, wh, dpi)
	return dipsToPhysical(dipW, dpi), dipsToPhysical(dipH, dpi)
}

// applyAdaptiveWindowSize sets HintMin (~720x520 DIPs) then the preferred
// client size from the window's monitor work area, both in physical pixels.
func applyAdaptiveWindowSize(w webview2.WebView) {
	if w == nil {
		return
	}
	hwnd := uintptr(w.Window())
	dpi := windowDPI(hwnd)
	ww, wh, ok := monitorWorkAreaPhysical(hwnd)
	if !ok || ww <= 0 || wh <= 0 {
		ww, wh, _ = primaryWorkAreaPhysical()
	}
	dipW, dipH := computeClientSizeDIPs(ww, wh, dpi)
	physW := dipsToPhysical(dipW, dpi)
	physH := dipsToPhysical(dipH, dpi)

	minW := dipsToPhysical(720, dpi)
	minH := dipsToPhysical(520, dpi)
	if minW > physW {
		minW = physW
	}
	if minH > physH {
		minH = physH
	}

	w.SetSize(minW, minH, webview2.HintMin)
	w.SetSize(physW, physH, webview2.HintNone)
}