// Copyright (c) 2021 Lars Pontoppidan. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
//
// vgret (V Graphics REgression Tool) aids in generating screenshots of various graphical `gg`
// based V applications, in a structured directory hierarchy, with the intent of either:
// * Generate a directory structure of screenshots/images to test against
//   (which, as an example, could later be pushed to a remote git repository)
// * Test for *visual* differences between two, structurally equal, directories
//
// vgret uses features and applications that is currently only available on Linux based distros:
// idiff - to programmatically find *visual* differences between two images:
//   - Ubuntu: `sudo apt install openimageio-tools`
//   - Arch:   `sudo pacman -S openimageio`
// Xvfb - to start a virtual X server framebuffer:
//   - Ubuntu: `sudo apt install xvfb`
//   - Arch:   `sudo pacman -S xorg-server-xvfb`
//
// For developers:
// For a quick overview of the generated images you can use `montage` from imagemagick to generate a "Contact Sheet":
// montage -verbose -label '%f' -font Helvetica -pointsize 10 -background '#000000' -fill 'gray' -define jpeg:size=200x200 -geometry 200x200+2+2 -auto-orient $(fd -t f . /path/to/vgret/out/dir) /tmp/montage.jpg
//   - Ubuntu: `sudo apt install imagemagick`
//   - Arch:   `sudo pacman -S imagemagick`
//
// To generate the reference images locally - or for uploading to a remote repo like `gg-regression-images`
// You can do the following:
// 1. `export DISPLAY=:99`                            # Start all graphical apps on DISPLAY 99
// 2. `Xvfb $DISPLAY -screen 0 1280x1024x24 &`        # Starts a virtual X11 screen buffer
// 3. `v gret -v /tmp/gg-regression-images`           # Generate reference images to /tmp/gg-regression-images
// 4. `v gret -v /tmp/test /tmp/gg-regression-images` # Test if the tests can pass locally by comparing to a fresh imageset
// 5. Visually check the images (you can get an overview by running the `montage` command above)
// 6. Upload to GitHub or keep locally for more testing/tweaking
//
// It's a known factor that the images generated on a local machine won't match the images generated on a remote machine by 100%.
// They will most likely differ by a small percentage - the comparison tool can be tweaked to accept these subtle changes,
// at the expense of slightly more inaccurate test results. For non-animated apps the percentage should be > 0.01.
// You can emulate or test these inaccuracies to some extend locally by simply running the test from a terminal using
// your physical X11 session display (Usually DISPLAY=:0).
//
// Read more about the options of `idiff` here: https://openimageio.readthedocs.io/en/latest/idiff.html
//
import os
import flag
import time
import toml

const (
	tool_name        = 'vgret'
	tool_version     = '0.0.2'
	tool_description = '\n  Dump and/or compare rendered frames of graphical apps
  both external and `gg` based apps is supported.

Examples:
  Generate screenshots to `/tmp/test`
    v gret /tmp/test
  Generate and compare screenshots in `/tmp/src` to existing screenshots in `/tmp/dst`
    v gret /tmp/src /tmp/dst
  Compare screenshots in `/tmp/src` to existing screenshots in `/tmp/dst`
    v gret --compare-only /tmp/src /tmp/dst
'
	tmp_dir    = os.join_path(os.vtmp_dir(), 'v', tool_name)
	runtime_os = os.user_os()
	v_root     = os.real_path(@VMODROOT)
)

const (
	supported_hosts           = ['linux']
	supported_capture_methods = ['gg_record', 'generic_screenshot']
	// External tool executables
	v_exe                     = os.getenv('VEXE')
	idiff_exe                 = os.find_abs_path_of_executable('idiff') or { '' }
)

const (
	embedded_toml    = $embed_file('vgret.defaults.toml', .zlib)
	default_toml     = embedded_toml.to_string()
	empty_toml_array = []toml.Any{}
	empty_toml_map   = map[string]toml.Any{}
)

struct Config {
	path string
mut:
	apps []AppConfig
}

struct CompareOptions {
mut:
	method string = 'idiff'
	flags  []string
}

struct CaptureRegion {
mut:
	x      int
	y      int
	width  int
	height int
}

fn (cr CaptureRegion) is_empty() bool {
	return cr.width == 0 && cr.height == 0
}

struct CaptureOptions {
mut:
	method  string = 'gg_record'
	wait_ms int // used by "generic_screenshot" to wait X milliseconds *after* execution of the app
	flags   []string
	regions []CaptureRegion
	env     map[string]string
}

fn (co CaptureOptions) validate() ! {
	if co.method !in supported_capture_methods {
		return error('capture method "${co.method}" is not supported. Supported methods are: ${supported_capture_methods}')
	}
}

struct AppConfig {
	compare  CompareOptions
	capture  CaptureOptions
	path     string
	abs_path string
mut:
	screenshots_path string
	screenshots      []string
}

struct Options {
	verbose      bool
	compare_only bool
	root_path    string
mut:
	config Config
}

fn (opt Options) verbose_execute(cmd string) os.Result {
	opt.verbose_eprintln('Running `${cmd}`')
	return os.execute(cmd)
}

fn (opt Options) verbose_eprintln(msg string) {
	if opt.verbose {
		eprintln(msg)
	}
}

fn main() {
	if runtime_os !in supported_hosts {
		eprintln('${tool_name} is currently only supported on ${supported_hosts} hosts')
		exit(1)
	}
	if os.args.len == 1 {
		eprintln('Usage: ${tool_name} PATH \n${tool_description}\n${tool_name} -h for more help...')
		exit(1)
	}

	mut fp := flag.new_flag_parser(os.args[1..])
	fp.application(tool_name)
	fp.version(tool_version)
	fp.description(tool_description)
	fp.arguments_description('PATH [PATH]')
	fp.skip_executable()

	show_help := fp.bool('help', `h`, false, 'Show this help text.')

	// Collect tool options
	mut opt := Options{
		verbose: fp.bool('verbose', `v`, false, "Be verbose about the tool's progress.")
		compare_only: fp.bool('compare-only', `c`, false, "Don't generate screenshots - only compare input directories")
		root_path: fp.string('root-path', `r`, v_root, 'Root path of the comparison')
	}

	toml_conf := fp.string('toml-config', `t`, default_toml, 'Path or string with TOML configuration')
	arg_paths := fp.finalize()!
	if show_help {
		println(fp.usage())
		exit(0)
	}

	if arg_paths.len == 0 {
		println(fp.usage())
		println('\nError missing arguments')
		exit(1)
	}

	if !os.exists(tmp_dir) {
		os.mkdir_all(tmp_dir)!
	}

	opt.config = new_config(opt.root_path, toml_conf) or { panic(err) }

	gen_in_path := arg_paths[0]
	if arg_paths.len >= 1 {
		generate_screenshots(mut opt, gen_in_path) or { panic(err) }
	}
	if arg_paths.len > 1 {
		target_path := arg_paths[1]
		path := opt.config.path
		all_paths_in_use := [path, gen_in_path, target_path]
		for path_in_use in all_paths_in_use {
			if !os.is_dir(path_in_use) {
				eprintln('`${path_in_use}` is not a directory')
				exit(1)
			}
		}
		if path == target_path || gen_in_path == target_path || gen_in_path == path {
			eprintln('Compare paths can not be the same directory `${path}`/`${target_path}`/`${gen_in_path}`')
			exit(1)
		}
		compare_screenshots(opt, gen_in_path, target_path)!
	}
}

fn generate_screenshots(mut opt Options, output_path string) ! {
	path := opt.config.path

	dst_path := output_path.trim_right('/')

	if !os.is_dir(path) {
		return error('`${path}` is not a directory')
	}

	for mut app_config in opt.config.apps {
		file := app_config.path
		app_path := app_config.abs_path

		mut rel_out_path := ''
		if os.is_file(app_path) {
			rel_out_path = os.dir(file)
		} else {
			rel_out_path = file
		}

		if app_config.capture.method == 'gg_record' {
			opt.verbose_eprintln('Compiling shaders (if needed) for `${file}`')
			sh_result := opt.verbose_execute('${os.quoted_path(v_exe)} shader ${os.quoted_path(app_path)}')
			if sh_result.exit_code != 0 {
				opt.verbose_eprintln('Skipping shader compile for `${file}` v shader failed with:\n${sh_result.output}')
				continue
			}
		}

		if !os.exists(dst_path) {
			opt.verbose_eprintln('Creating output path `${dst_path}`')
			os.mkdir_all(dst_path) or { return error('Failed making directory `${dst_path}`') }
		}

		screenshot_path := os.join_path(dst_path, rel_out_path)
		if !os.exists(screenshot_path) {
			os.mkdir_all(screenshot_path) or {
				return error('Failed making screenshot path `${screenshot_path}`')
			}
		}

		app_config.screenshots_path = screenshot_path
		app_config.screenshots = take_screenshots(opt, app_config) or {
			return error('Failed taking screenshots of `${app_path}`:\n${err.msg()}')
		}
	}
}

fn compare_screenshots(opt Options, output_path string, target_path string) ! {
	mut fails := map[string]string{}
	mut warns := map[string]string{}
	for app_config in opt.config.apps {
		screenshots := app_config.screenshots
		opt.verbose_eprintln('Comparing ${screenshots.len} screenshots in `${output_path}` with `${target_path}`')
		for screenshot in screenshots {
			relative_screenshot := screenshot.all_after(output_path + os.path_separator)

			src := screenshot
			target := os.join_path(target_path, relative_screenshot)
			opt.verbose_eprintln('Comparing `${src}` with `${target}` with ${app_config.compare.method}')

			if app_config.compare.method == 'idiff' {
				if idiff_exe == '' {
					return error('${tool_name} need the `idiff` tool installed. It can be installed on Ubuntu with `sudo apt install openimageio-tools`')
				}
				diff_file := os.join_path(os.vtmp_dir(), os.file_name(src).all_before_last('.') +
					'.diff.tif')
				flags := app_config.compare.flags.join(' ')
				diff_cmd := '${os.quoted_path(idiff_exe)} ${flags} -abs -od -o ${os.quoted_path(diff_file)} -abs ${os.quoted_path(src)} ${os.quoted_path(target)}'
				result := opt.verbose_execute(diff_cmd)
				if result.exit_code == 0 {
					opt.verbose_eprintln('OUTPUT: \n${result.output}')
				}
				if result.exit_code != 0 {
					eprintln('OUTPUT: \n${result.output}')
					if result.exit_code == 1 {
						warns[src] = target
					} else {
						fails[src] = target
					}
				}
			}
		}
	}

	if warns.len > 0 {
		eprintln('--- WARNINGS ---')
		eprintln('The following files had warnings when compared to their targets')
		for warn_src, warn_target in warns {
			eprintln('${warn_src} ~= ${warn_target}')
		}
	}
	if fails.len > 0 {
		eprintln('--- ERRORS ---')
		eprintln('The following files did not match their targets')
		for fail_src, fail_target in fails {
			eprintln('${fail_src} != ${fail_target}')
		}
		first := fails.keys()[0]
		fail_copy := os.join_path(os.vtmp_dir(), 'fail.' + first.all_after_last('.'))
		os.cp(first, fail_copy)!
		eprintln('First failed file `${first}` is copied to `${fail_copy}`')

		diff_file := os.join_path(os.vtmp_dir(), os.file_name(first).all_before_last('.') +
			'.diff.tif')
		diff_copy := os.join_path(os.vtmp_dir(), 'diff.tif')
		if os.is_file(diff_file) {
			os.cp(diff_file, diff_copy)!
			eprintln('First failed diff file `${diff_file}` is copied to `${diff_copy}`')
			eprintln('Removing alpha channel from ${diff_copy} ...')
			final_fail_result_file := os.join_path(os.vtmp_dir(), 'diff.png')
			opt.verbose_execute('convert ${os.quoted_path(diff_copy)} -alpha off ${os.quoted_path(final_fail_result_file)}')
			eprintln('Final diff file: `${final_fail_result_file}`')
		}
		exit(1)
	}
}

fn take_screenshots(opt Options, app AppConfig) ![]string {
	out_path := app.screenshots_path
	if !opt.compare_only {
		opt.verbose_eprintln('Taking screenshot(s) of `${app.path}` to `${out_path}`')
		match app.capture.method {
			'gg_record' {
				for k, v in app.capture.env {
					rv := v.replace('\$OUT_PATH', out_path)
					opt.verbose_eprintln('Setting ENV `${k}` = ${rv} ...')
					os.setenv('${k}', rv, true)
				}

				flags := app.capture.flags.join(' ')
				result := opt.verbose_execute('${os.quoted_path(v_exe)} ${flags} -d gg_record run ${os.quoted_path(app.abs_path)}')
				if result.exit_code != 0 {
					return error('Failed taking screenshot of `${app.abs_path}`:\n${result.output}')
				}
			}
			'generic_screenshot' {
				for k, v in app.capture.env {
					rv := v.replace('\$OUT_PATH', out_path)
					opt.verbose_eprintln('Setting ENV `${k}` = ${rv} ...')
					os.setenv('${k}', rv, true)
				}

				existing_screenshots := get_app_screenshots(out_path, app)!

				flags := app.capture.flags

				if !os.exists(app.abs_path) {
					return error('Failed starting app `${app.abs_path}`, the path does not exist')
				}
				opt.verbose_eprintln('Running ${app.abs_path} ${flags}')
				mut p_app := os.new_process(app.abs_path)
				p_app.set_args(flags)
				p_app.set_redirect_stdio()
				p_app.run()

				if !p_app.is_alive() {
					output := p_app.stdout_read() + '\n' + p_app.stderr_read()
					return error('Failed starting app `${app.abs_path}` (before screenshot):\n${output}')
				}
				if app.capture.wait_ms > 0 {
					opt.verbose_eprintln('Waiting ${app.capture.wait_ms} before capturing')
					time.sleep(app.capture.wait_ms * time.millisecond)
				}
				if !p_app.is_alive() {
					output := p_app.stdout_slurp() + '\n' + p_app.stderr_slurp()
					return error('App `${app.abs_path}` exited (${p_app.code}) before a screenshot could be captured:\n${output}')
				}
				// Use ImageMagick's `import` tool to take the screenshot
				out_file := os.join_path(out_path, os.file_name(app.path) +
					'_screenshot_${existing_screenshots.len:02}.png')
				result := opt.verbose_execute('import -window root "${out_file}"')
				if result.exit_code != 0 {
					p_app.signal_kill()
					return error('Failed taking screenshot of `${app.abs_path}` to "${out_file}":\n${result.output}')
				}

				// When using regions the capture is split up into regions.len
				// And name the output based on each region's properties
				if app.capture.regions.len > 0 {
					for region in app.capture.regions {
						region_id := 'x${region.x}y${region.y}w${region.width}h${region.height}'
						region_out_file := os.join_path(out_path, os.file_name(app.path) +
							'_screenshot_${existing_screenshots.len:02}_region_${region_id}.png')
						// If the region is empty (w, h == 0, 0) infer a full screenshot,
						// This allows for capturing both regions *and* the complete screen
						if region.is_empty() {
							os.cp(out_file, region_out_file) or {
								return error('Failed copying original screenshot "${out_file}" to region file "${region_out_file}"')
							}
							continue
						}
						extract_result := opt.verbose_execute('convert -extract ${region.width}x${region.height}+${region.x}+${region.y} "${out_file}" "${region_out_file}"')
						if extract_result.exit_code != 0 {
							p_app.signal_kill()
							return error('Failed extracting region ${region_id} from screenshot of `${app.abs_path}` to "${region_out_file}":\n${result.output}')
						}
					}
					// When done, remove the original file that was split into regions.
					opt.verbose_eprintln('Removing "${out_file}" (region mode)')
					os.rm(out_file) or {
						return error('Failed removing original screenshot "${out_file}"')
					}
				}
				p_app.signal_kill()
			}
			else {
				return error('Unsupported capture method "${app.capture.method}"')
			}
		}
	}
	return get_app_screenshots(out_path, app)!
}

fn get_app_screenshots(path string, app AppConfig) ![]string {
	mut screenshots := []string{}
	shots := os.ls(path) or { return error('Failed listing dir `${path}`') }
	for shot in shots {
		if shot.starts_with(os.file_name(app.path).all_before_last('.')) {
			screenshots << os.join_path(path, shot)
		}
	}
	return screenshots
}

fn new_config(root_path string, toml_config string) !Config {
	doc := if os.is_file(toml_config) {
		toml.parse_file(toml_config) or { return error(err.msg()) }
	} else {
		toml.parse_text(toml_config) or { return error(err.msg()) }
	}

	path := os.real_path(root_path).trim_right('/')

	compare_method := doc.value('compare.method').default_to('idiff').string()
	compare_flags := doc.value('compare.flags').default_to(empty_toml_array).array().as_strings()
	default_compare := CompareOptions{
		method: compare_method
		flags: compare_flags
	}
	capture_method := doc.value('capture.method').default_to('gg_record').string()
	capture_flags := doc.value('capture.flags').default_to(empty_toml_array).array().as_strings()
	capture_regions_any := doc.value('capture.regions').default_to(empty_toml_array).array()
	mut capture_regions := []CaptureRegion{}
	for capture_region_any in capture_regions_any {
		region := CaptureRegion{
			x: capture_region_any.value('x').default_to(0).int()
			y: capture_region_any.value('y').default_to(0).int()
			width: capture_region_any.value('width').default_to(0).int()
			height: capture_region_any.value('height').default_to(0).int()
		}
		capture_regions << region
	}
	capture_wait_ms := doc.value('capture.wait_ms').default_to(0).int()
	capture_env := doc.value('capture.env').default_to(empty_toml_map).as_map()
	mut env_map := map[string]string{}
	for k, v in capture_env {
		env_map[k] = v.string()
	}
	default_capture := CaptureOptions{
		method: capture_method
		wait_ms: capture_wait_ms
		flags: capture_flags
		regions: capture_regions
		env: env_map
	}

	apps_any := doc.value('apps').default_to(empty_toml_array).array()
	mut apps := []AppConfig{cap: apps_any.len}
	for app_any in apps_any {
		rel_path := app_any.value('path').string().trim_right('/')

		// Merge, per app, overwrites
		mut merged_compare := CompareOptions{}
		merged_compare.method = app_any.value('compare.method').default_to(default_compare.method).string()
		merged_compare_flags := app_any.value('compare.flags').default_to(empty_toml_array).array().as_strings()
		if merged_compare_flags.len > 0 {
			merged_compare.flags = merged_compare_flags
		} else {
			merged_compare.flags = default_compare.flags
		}

		mut merged_capture := CaptureOptions{}
		merged_capture.method = app_any.value('capture.method').default_to(default_capture.method).string()
		merged_capture_flags := app_any.value('capture.flags').default_to(empty_toml_array).array().as_strings()
		if merged_capture_flags.len > 0 {
			merged_capture.flags = merged_capture_flags
		} else {
			merged_capture.flags = default_capture.flags
		}

		app_capture_regions_any := app_any.value('capture.regions').default_to(empty_toml_array).array()
		mut app_capture_regions := []CaptureRegion{}
		for capture_region_any in app_capture_regions_any {
			region := CaptureRegion{
				x: capture_region_any.value('x').default_to(0).int()
				y: capture_region_any.value('y').default_to(0).int()
				width: capture_region_any.value('width').default_to(0).int()
				height: capture_region_any.value('height').default_to(0).int()
			}
			app_capture_regions << region
		}
		mut merged_capture_regions := []CaptureRegion{}
		for default_capture_region in default_capture.regions {
			if default_capture_region !in app_capture_regions {
				merged_capture_regions << default_capture_region
			}
		}
		for app_capture_region in app_capture_regions {
			if app_capture_region !in default_capture.regions {
				merged_capture_regions << app_capture_region
			}
		}
		merged_capture.regions = merged_capture_regions

		merged_capture.wait_ms = app_any.value('capture.wait_ms').default_to(default_capture.wait_ms).int()
		merge_capture_env := app_any.value('capture.env').default_to(empty_toml_map).as_map()
		mut merge_env_map := default_capture.env.clone()
		for k, v in merge_capture_env {
			merge_env_map[k] = v.string()
		}
		for k, v in merge_env_map {
			merged_capture.env[k] = v
		}

		merged_capture.validate()!

		app_config := AppConfig{
			compare: merged_compare
			capture: merged_capture
			path: rel_path
			abs_path: os.join_path(path, rel_path).trim_right('/')
		}
		apps << app_config
	}

	return Config{
		apps: apps
		path: path
	}
}