// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license that can be found in the LICENSE file.
module gg

import sokol.sfons
import sokol.sgl
import gx
import os

enum FontVariant {
	normal = 0
	bold
	mono
	italic
}

struct FT {
pub:
	fons        &C.FONScontext
	font_normal int
	font_bold   int
	font_mono   int
	font_italic int
	scale       f32 = 1.0
}

struct FTConfig {
	font_path             string
	custom_bold_font_path string
	scale                 f32 = 1.0
	font_size             int
	bytes_normal          []byte
	bytes_bold            []byte
	bytes_mono            []byte
	bytes_italic          []byte
}

struct StringToRender {
	x    int
	y    int
	text string
	cfg  gx.TextCfg
}

fn new_ft(c FTConfig) ?&FT {
	if c.font_path == '' {
		if c.bytes_normal.len > 0 {
			fons := sfons.create(512, 512, 1)
			bytes_normal := c.bytes_normal
			bytes_bold := if c.bytes_bold.len > 0 {
				c.bytes_bold
			} else {
				debug_font_println('setting bold variant to normal')
				bytes_normal
			}
			bytes_mono := if c.bytes_mono.len > 0 {
				c.bytes_mono
			} else {
				debug_font_println('setting mono variant to normal')
				bytes_normal
			}
			bytes_italic := if c.bytes_italic.len > 0 {
				c.bytes_italic
			} else {
				debug_font_println('setting italic variant to normal')
				bytes_normal
			}

			return &FT{
				fons: fons
				font_normal: C.fonsAddFontMem(fons, 'sans', bytes_normal.data, bytes_normal.len,
					false)
				font_bold: C.fonsAddFontMem(fons, 'sans', bytes_bold.data, bytes_bold.len,
					false)
				font_mono: C.fonsAddFontMem(fons, 'sans', bytes_mono.data, bytes_mono.len,
					false)
				font_italic: C.fonsAddFontMem(fons, 'sans', bytes_italic.data, bytes_italic.len,
					false)
				scale: c.scale
			}
		} else {
			// Load default font
		}
	}

	if c.font_path == '' || !os.exists(c.font_path) {
		$if !android {
			println('failed to load font "$c.font_path"')
			return none
		}
	}

	mut bytes := []byte{}
	$if android {
		// First try any filesystem paths
		bytes = os.read_bytes(c.font_path) or { []byte{} }
		if bytes.len == 0 {
			// ... then try the APK asset path
			bytes = os.read_apk_asset(c.font_path) or {
				println('failed to load font "$c.font_path"')
				return none
			}
		}
	} $else {
		bytes = os.read_bytes(c.font_path) or {
			println('failed to load font "$c.font_path"')
			return none
		}
	}
	bold_path := if c.custom_bold_font_path != '' {
		c.custom_bold_font_path
	} else {
		get_font_path_variant(c.font_path, .bold)
	}
	bytes_bold := os.read_bytes(bold_path) or {
		debug_font_println('failed to load font "$bold_path"')
		bytes
	}
	mono_path := get_font_path_variant(c.font_path, .mono)
	bytes_mono := os.read_bytes(mono_path) or {
		debug_font_println('failed to load font "$mono_path"')
		bytes
	}
	italic_path := get_font_path_variant(c.font_path, .italic)
	bytes_italic := os.read_bytes(italic_path) or {
		debug_font_println('failed to load font "$italic_path"')
		bytes
	}
	fons := sfons.create(512, 512, 1)
	return &FT{
		fons: fons
		font_normal: C.fonsAddFontMem(fons, 'sans', bytes.data, bytes.len, false)
		font_bold: C.fonsAddFontMem(fons, 'sans', bytes_bold.data, bytes_bold.len, false)
		font_mono: C.fonsAddFontMem(fons, 'sans', bytes_mono.data, bytes_mono.len, false)
		font_italic: C.fonsAddFontMem(fons, 'sans', bytes_italic.data, bytes_italic.len,
			false)
		scale: c.scale
	}
}

pub fn (ctx &Context) set_cfg(cfg gx.TextCfg) {
	if !ctx.font_inited {
		return
	}
	if cfg.bold {
		ctx.ft.fons.set_font(ctx.ft.font_bold)
	} else if cfg.mono {
		ctx.ft.fons.set_font(ctx.ft.font_mono)
	} else if cfg.italic {
		ctx.ft.fons.set_font(ctx.ft.font_italic)
	} else {
		ctx.ft.fons.set_font(ctx.ft.font_normal)
	}
	scale := if ctx.ft.scale == 0 { f32(1) } else { ctx.ft.scale }
	size := if cfg.mono { cfg.size - 2 } else { cfg.size }
	ctx.ft.fons.set_size(scale * f32(size))
	C.fonsSetAlign(ctx.ft.fons, int(cfg.align) | int(cfg.vertical_align))
	color := C.sfons_rgba(cfg.color.r, cfg.color.g, cfg.color.b, cfg.color.a)
	if cfg.color.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	C.fonsSetColor(ctx.ft.fons, color)
	ascender := f32(0.0)
	descender := f32(0.0)
	lh := f32(0.0)
	ctx.ft.fons.vert_metrics(&ascender, &descender, &lh)
}

pub fn (ctx &Context) draw_text(x int, y int, text_ string, cfg gx.TextCfg) {
	$if macos {
		if ctx.native_rendering {
			if cfg.align == gx.align_right {
				width := ctx.text_width(text_)
				C.darwin_draw_string(x - width, ctx.height - y, text_, cfg)
			} else {
				C.darwin_draw_string(x, ctx.height - y, text_, cfg)
			}
			return
		}
	}
	if !ctx.font_inited {
		eprintln('gg: draw_text(): font not initialized')
		return
	}
	// text := text_.trim_space() // TODO remove/optimize
	// mut text := text_
	// if text.contains('\t') {
	// text = text.replace('\t', '    ')
	// }
	ctx.set_cfg(cfg)
	scale := if ctx.ft.scale == 0 { f32(1) } else { ctx.ft.scale }
	C.fonsDrawText(ctx.ft.fons, x * scale, y * scale, text_.str, 0) // TODO: check offsets/alignment
}

pub fn (ctx &Context) draw_text_def(x int, y int, text string) {
	ctx.draw_text(x, y, text, {})
}

/*
pub fn (mut gg FT) init_font() {
}
*/
pub fn (ft &FT) flush() {
	sfons.flush(ft.fons)
}

pub fn (ctx &Context) text_width(s string) int {
	$if macos {
		if ctx.native_rendering {
			return C.darwin_text_width(s)
		}
	}
	// ctx.set_cfg(cfg) TODO
	if !ctx.font_inited {
		return 0
	}
	mut buf := [4]f32{}
	C.fonsTextBounds(ctx.ft.fons, 0, 0, s.str, 0, &buf[0])
	if s.ends_with(' ') {
		return int((buf[2] - buf[0]) / ctx.scale) +
			ctx.text_width('i') // TODO fix this in fontstash?
	}
	res := int((buf[2] - buf[0]) / ctx.scale)
	// println('TW "$s" = $res')
	$if macos {
		if ctx.native_rendering {
			return res * 2
		}
	}
	return int((buf[2] - buf[0]) / ctx.scale)
}

pub fn (ctx &Context) text_height(s string) int {
	// ctx.set_cfg(cfg) TODO
	if !ctx.font_inited {
		return 0
	}
	mut buf := [4]f32{}
	C.fonsTextBounds(ctx.ft.fons, 0, 0, s.str, 0, &buf[0])
	return int((buf[3] - buf[1]) / ctx.scale)
}

pub fn (ctx &Context) text_size(s string) (int, int) {
	// ctx.set_cfg(cfg) TODO
	if !ctx.font_inited {
		return 0, 0
	}
	mut buf := [4]f32{}
	C.fonsTextBounds(ctx.ft.fons, 0, 0, s.str, 0, &buf[0])
	return int((buf[2] - buf[0]) / ctx.scale), int((buf[3] - buf[1]) / ctx.scale)
}

pub fn system_font_path() string {
	env_font := os.getenv('VUI_FONT')
	if env_font != '' && os.exists(env_font) {
		return env_font
	}
	$if windows {
		return 'C:\\Windows\\Fonts\\arial.ttf'
	}
	mut fonts := ['Ubuntu-R.ttf', 'Arial.ttf', 'LiberationSans-Regular.ttf', 'NotoSans-Regular.ttf',
		'FreeSans.ttf', 'DejaVuSans.ttf']
	$if macos {
		fonts = ['/System/Library/Fonts/SFNS.ttf', '/System/Library/Fonts/SFNSText.ttf',
			'/Library/Fonts/Arial.ttf',
		]
		for font in fonts {
			if os.is_file(font) {
				return font
			}
		}
	}
	$if android {
		xml_files := ['/system/etc/system_fonts.xml', '/system/etc/fonts.xml',
			'/etc/system_fonts.xml', '/etc/fonts.xml', '/data/fonts/fonts.xml',
			'/etc/fallback_fonts.xml',
		]
		font_locations := ['/system/fonts', '/data/fonts']
		for xml_file in xml_files {
			if os.is_file(xml_file) && os.is_readable(xml_file) {
				xml := os.read_file(xml_file) or { continue }
				lines := xml.split('\n')
				mut candidate_font := ''
				for line in lines {
					if line.contains('<font') {
						candidate_font = line.all_after('>').all_before('<').trim(' \n\t\r')
						if candidate_font.contains('.ttf') {
							for location in font_locations {
								candidate_path := os.join_path(location, candidate_font)
								if os.is_file(candidate_path) && os.is_readable(candidate_path) {
									return candidate_path
								}
							}
						}
					}
				}
			}
		}
	}
	s := os.execute('fc-list')
	if s.exit_code != 0 {
		panic('failed to fetch system fonts')
	}
	system_fonts := s.output.split('\n')
	for line in system_fonts {
		for font in fonts {
			if line.contains(font) && line.contains(':') {
				res := line.all_before(':')
				println('Using font $res')
				return res
			}
		}
	}
	panic('failed to init the font')
}

fn get_font_path_variant(font_path string, variant FontVariant) string {
	// TODO: find some way to make this shorter and more eye-pleasant
	// NotoSans, LiberationSans, DejaVuSans, Arial and SFNS should work
	mut fpath := font_path.replace('.ttf', '')
	match variant {
		.normal {}
		.bold {
			if fpath.ends_with('-Regular') {
				fpath = fpath.replace('-Regular', '-Bold')
			} else if fpath.starts_with('DejaVuSans') {
				fpath += '-Bold'
			} else if fpath.to_lower().starts_with('arial') {
				fpath += 'bd'
			} else {
				fpath += '-bold'
			}
			$if macos {
				if os.exists('SFNS-bold') {
					fpath = 'SFNS-bold'
				}
			}
		}
		.italic {
			if fpath.ends_with('-Regular') {
				fpath = fpath.replace('-Regular', '-Italic')
			} else if fpath.starts_with('DejaVuSans') {
				fpath += '-Oblique'
			} else if fpath.to_lower().starts_with('arial') {
				fpath += 'i'
			} else {
				fpath += 'Italic'
			}
		}
		.mono {
			if !fpath.ends_with('Mono-Regular') && fpath.ends_with('-Regular') {
				fpath = fpath.replace('-Regular', 'Mono-Regular')
			} else if fpath.to_lower().starts_with('arial') {
				// Arial has no mono variant
			} else {
				fpath += 'Mono'
			}
		}
	}
	return fpath + '.ttf'
}

fn debug_font_println(s string) {
	$if debug_font ? {
		println(s)
	}
}