// Package ui internal helpers — theme palette + system-theme detection.

package ui

import (
	"image/color"

	"gioui.org/font/gofont"
	"gioui.org/text"
	"gioui.org/widget/material"
)

// themeMode is one of the user-selectable theme settings.
type themeMode string

const (
	themeSystem themeMode = "system"
	themeLight  themeMode = "light"
	themeDark   themeMode = "dark"
)

// themePalette holds the small set of colors the app itself draws
// (toast, dividers, ring background, etc). The material.Theme handles
// button + body text colors via its own palette.
type themePalette struct {
	Background   color.NRGBA
	OnBackground color.NRGBA
	Divider      color.NRGBA
	RingBg       color.NRGBA
	RingFg       color.NRGBA
	RingFgWarn   color.NRGBA
	ToastBg      color.NRGBA
	ToastFg      color.NRGBA
	ErrorFg      color.NRGBA
	DialogBg     color.NRGBA
	DialogBorder color.NRGBA
	ScrimBg      color.NRGBA // backdrop behind modal dialogs
	MutedFg      color.NRGBA // for placeholder / hint text
}

func lightPalette() themePalette {
	return themePalette{
		Background:   color.NRGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		OnBackground: color.NRGBA{R: 0x10, G: 0x10, B: 0x10, A: 0xff},
		Divider:      color.NRGBA{R: 0xe0, G: 0xe0, B: 0xe0, A: 0xff},
		RingBg:       color.NRGBA{R: 0xd8, G: 0xd8, B: 0xd8, A: 0xff},
		RingFg:       color.NRGBA{R: 0x10, G: 0x70, B: 0xff, A: 0xff},
		RingFgWarn:   color.NRGBA{R: 0xd0, G: 0x30, B: 0x30, A: 0xff},
		ToastBg:      color.NRGBA{R: 0x20, G: 0x20, B: 0x20, A: 0xe0},
		ToastFg:      color.NRGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		ErrorFg:      color.NRGBA{R: 0xc0, G: 0x00, B: 0x00, A: 0xff},
		DialogBg:     color.NRGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff},
		DialogBorder: color.NRGBA{R: 0x55, G: 0x55, B: 0x55, A: 0xff},
		ScrimBg:      color.NRGBA{R: 0x00, G: 0x00, B: 0x00, A: 0x60},
		MutedFg:      color.NRGBA{R: 0x80, G: 0x80, B: 0x80, A: 0xff},
	}
}

func darkPalette() themePalette {
	return themePalette{
		Background:   color.NRGBA{R: 0x1e, G: 0x1e, B: 0x1e, A: 0xff},
		OnBackground: color.NRGBA{R: 0xf0, G: 0xf0, B: 0xf0, A: 0xff},
		Divider:      color.NRGBA{R: 0x38, G: 0x38, B: 0x38, A: 0xff},
		RingBg:       color.NRGBA{R: 0x3a, G: 0x3a, B: 0x3a, A: 0xff},
		RingFg:       color.NRGBA{R: 0x4d, G: 0xa3, B: 0xff, A: 0xff},
		RingFgWarn:   color.NRGBA{R: 0xff, G: 0x6b, B: 0x6b, A: 0xff},
		ToastBg:      color.NRGBA{R: 0xf0, G: 0xf0, B: 0xf0, A: 0xee},
		ToastFg:      color.NRGBA{R: 0x10, G: 0x10, B: 0x10, A: 0xff},
		ErrorFg:      color.NRGBA{R: 0xff, G: 0x6b, B: 0x6b, A: 0xff},
		DialogBg:     color.NRGBA{R: 0x2a, G: 0x2a, B: 0x2a, A: 0xff},
		DialogBorder: color.NRGBA{R: 0x60, G: 0x60, B: 0x60, A: 0xff},
		ScrimBg:      color.NRGBA{R: 0x00, G: 0x00, B: 0x00, A: 0x90},
		MutedFg:      color.NRGBA{R: 0x90, G: 0x90, B: 0x90, A: 0xff},
	}
}

// buildTheme returns a fresh material.Theme + companion palette for the
// requested mode. "system" resolves via systemPrefersDark (Windows
// registry on win, false elsewhere).
func buildTheme(mode themeMode) (*material.Theme, themePalette) {
	resolved := mode
	if resolved == "" || resolved == themeSystem {
		if systemPrefersDark() {
			resolved = themeDark
		} else {
			resolved = themeLight
		}
	}
	var pal themePalette
	if resolved == themeDark {
		pal = darkPalette()
	} else {
		pal = lightPalette()
	}

	th := material.NewTheme()
	th.Shaper = text.NewShaper(text.WithCollection(gofont.Collection()))
	th.Palette.Bg = pal.Background
	th.Palette.Fg = pal.OnBackground
	if resolved == themeDark {
		th.Palette.ContrastBg = color.NRGBA{R: 0x4d, G: 0xa3, B: 0xff, A: 0xff}
		th.Palette.ContrastFg = color.NRGBA{R: 0x10, G: 0x10, B: 0x10, A: 0xff}
	}
	return th, pal
}

// normalizeThemeMode coerces an arbitrary config string into one of the
// known modes. Unknown values fall back to "system".
func normalizeThemeMode(s string) themeMode {
	switch themeMode(s) {
	case themeLight, themeDark, themeSystem:
		return themeMode(s)
	}
	return themeSystem
}

// activePalette holds the palette of the currently-rendered theme. Set
// once per frame at the top of drawFrame so shared helpers (toast,
// dividers, dialog backdrops) can colour themselves without dragging a
// palette argument through every signature. Gio invokes drawFrame on
// the single UI goroutine so plain assignment is safe.
var activePalette = lightPalette()