use std::{
	collections::BTreeSet,
	ffi::{OsStr, OsString},
	fs::canonicalize,
	mem::take,
	path::{Path, PathBuf},
	str::FromStr,
	time::Duration,
};

use clap::{
	builder::TypedValueParser, error::ErrorKind, Arg, Command, CommandFactory, Parser, ValueEnum,
	ValueHint,
};
use miette::{IntoDiagnostic, Result};
use tokio::{fs::File, io::AsyncReadExt};
use tracing::{debug, info, trace, warn};
use tracing_appender::non_blocking::WorkerGuard;
use watchexec::{paths::PATH_SEPARATOR, sources::fs::WatchedPath};
use watchexec_signals::Signal;

use crate::filterer::parse::parse_filter_program;

mod logging;

const OPTSET_FILTERING: &str = "Filtering";
const OPTSET_COMMAND: &str = "Command";
const OPTSET_DEBUGGING: &str = "Debugging";
const OPTSET_OUTPUT: &str = "Output";

include!(env!("BOSION_PATH"));

/// Execute commands when watched files change.
///
/// Recursively monitors the current directory for changes, executing the command when a filesystem
/// change is detected (among other event sources). By default, watchexec uses efficient
/// kernel-level mechanisms to watch for changes.
///
/// At startup, the specified command is run once, and watchexec begins monitoring for changes.
///
/// Examples:
///
/// Rebuild a project when source files change:
///
///   $ watchexec make
///
/// Watch all HTML, CSS, and JavaScript files for changes:
///
///   $ watchexec -e html,css,js make
///
/// Run tests when source files change, clearing the screen each time:
///
///   $ watchexec -c make test
///
/// Launch and restart a node.js server:
///
///   $ watchexec -r node app.js
///
/// Watch lib and src directories for changes, rebuilding each time:
///
///   $ watchexec -w lib -w src make
#[derive(Debug, Clone, Parser)]
#[command(
	name = "watchexec",
	bin_name = "watchexec",
	author,
	version,
	long_version = Bosion::LONG_VERSION,
	after_help = "Want more detail? Try the long '--help' flag!",
	after_long_help = "Use @argfile as first argument to load arguments from the file 'argfile' (one argument per line) which will be inserted in place of the @argfile (further arguments on the CLI will override or add onto those in the file).\n\nDidn't expect this much output? Use the short '-h' flag to get short help.",
	hide_possible_values = true,
)]
#[cfg_attr(debug_assertions, command(before_help = "⚠ DEBUG BUILD ⚠"))]
#[cfg_attr(
	feature = "dev-console",
	command(before_help = "⚠ DEV CONSOLE ENABLED ⚠")
)]
#[allow(clippy::struct_excessive_bools)]
pub struct Args {
	/// Command to run on changes
	///
	/// It's run when events pass filters and the debounce period (and once at startup unless
	/// '--postpone' is given). If you pass flags to the command, you should separate it with --
	/// though that is not strictly required.
	///
	/// Examples:
	///
	///   $ watchexec -w src npm run build
	///
	///   $ watchexec -w src -- rsync -a src dest
	///
	/// Take care when using globs or other shell expansions in the command. Your shell may expand
	/// them before ever passing them to Watchexec, and the results may not be what you expect.
	/// Compare:
	///
	///   $ watchexec echo src/*.rs
	///
	///   $ watchexec echo 'src/*.rs'
	///
	///   $ watchexec --shell=none echo 'src/*.rs'
	///
	/// Behaviour depends on the value of '--shell': for all except 'none', every part of the
	/// command is joined together into one string with a single ascii space character, and given to
	/// the shell as described in the help for '--shell'. For 'none', each distinct element the
	/// command is passed as per the execvp(3) convention: first argument is the program, as a path
	/// or searched for in the 'PATH' environment variable, rest are arguments.
	#[arg(
		trailing_var_arg = true,
		num_args = 1..,
		value_hint = ValueHint::CommandString,
		value_name = "COMMAND",
		required_unless_present_any = ["completions", "manual", "only_emit_events"],
	)]
	pub command: Vec<String>,

	/// Watch a specific file or directory
	///
	/// By default, Watchexec watches the current directory.
	///
	/// When watching a single file, it's often better to watch the containing directory instead,
	/// and filter on the filename. Some editors may replace the file with a new one when saving,
	/// and some platforms may not detect that or further changes.
	///
	/// Upon starting, Watchexec resolves a "project origin" from the watched paths. See the help
	/// for '--project-origin' for more information.
	///
	/// This option can be specified multiple times to watch multiple files or directories.
	///
	/// The special value '/dev/null', provided as the only path watched, will cause Watchexec to
	/// not watch any paths. Other event sources (like signals or key events) may still be used.
	#[arg(
		short = 'w',
		long = "watch",
		help_heading = OPTSET_FILTERING,
		value_hint = ValueHint::AnyPath,
		value_name = "PATH",
	)]
	pub recursive_paths: Vec<PathBuf>,

	/// Watch a specific directory, non-recursively
	///
	/// Unlike '-w', folders watched with this option are not recursed into.
	///
	/// This option can be specified multiple times to watch multiple directories non-recursively.
	#[arg(
		short = 'W',
		long = "watch-non-recursive",
		help_heading = OPTSET_FILTERING,
		value_hint = ValueHint::AnyPath,
		value_name = "PATH",
	)]
	pub non_recursive_paths: Vec<PathBuf>,

	#[doc(hidden)]
	#[arg(skip)]
	pub paths: Vec<WatchedPath>,

	/// Clear screen before running command
	///
	/// If this doesn't completely clear the screen, try '--clear=reset'.
	#[arg(
		short = 'c',
		long = "clear",
		help_heading = OPTSET_OUTPUT,
		num_args = 0..=1,
		default_missing_value = "clear",
		value_name = "MODE",
	)]
	pub screen_clear: Option<ClearMode>,

	/// What to do when receiving events while the command is running
	///
	/// Default is to 'do-nothing', which ignores events while the command is running, so that
	/// changes that occur due to the command are ignored, like compilation outputs. You can also
	/// use 'queue' which will run the command once again when the current run has finished if any
	/// events occur while it's running, or 'restart', which terminates the running command and starts
	/// a new one. Finally, there's 'signal', which only sends a signal; this can be useful with
	/// programs that can reload their configuration without a full restart.
	///
	/// The signal can be specified with the '--signal' option.
	#[arg(
		short,
		long,
		default_value = "do-nothing",
		hide_default_value = true,
		value_name = "MODE"
	)]
	pub on_busy_update: OnBusyUpdate,

	/// Restart the process if it's still running
	///
	/// This is a shorthand for '--on-busy-update=restart'.
	#[arg(
		short,
		long,
		conflicts_with_all = ["on_busy_update"],
	)]
	pub restart: bool,

	/// Send a signal to the process when it's still running
	///
	/// Specify a signal to send to the process when it's still running. This implies
	/// '--on-busy-update=signal'; otherwise the signal used when that mode is 'restart' is
	/// controlled by '--stop-signal'.
	///
	/// See the long documentation for '--stop-signal' for syntax.
	///
	/// Signals are not supported on Windows at the moment, and will always be overridden to 'kill'.
	/// See '--stop-signal' for more on Windows "signals".
	#[arg(
		short,
		long,
		conflicts_with_all = ["restart"],
		value_name = "SIGNAL"
	)]
	pub signal: Option<Signal>,

	/// Signal to send to stop the command
	///
	/// This is used by 'restart' and 'signal' modes of '--on-busy-update' (unless '--signal' is
	/// provided). The restart behaviour is to send the signal, wait for the command to exit, and if
	/// it hasn't exited after some time (see '--timeout-stop'), forcefully terminate it.
	///
	/// The default on unix is "SIGTERM".
	///
	/// Input is parsed as a full signal name (like "SIGTERM"), a short signal name (like "TERM"),
	/// or a signal number (like "15"). All input is case-insensitive.
	///
	/// On Windows this option is technically supported but only supports the "KILL" event, as
	/// Watchexec cannot yet deliver other events. Windows doesn't have signals as such; instead it
	/// has termination (here called "KILL" or "STOP") and "CTRL+C", "CTRL+BREAK", and "CTRL+CLOSE"
	/// events. For portability the unix signals "SIGKILL", "SIGINT", "SIGTERM", and "SIGHUP" are
	/// respectively mapped to these.
	#[arg(long, value_name = "SIGNAL")]
	pub stop_signal: Option<Signal>,

	/// Time to wait for the command to exit gracefully
	///
	/// This is used by the 'restart' mode of '--on-busy-update'. After the graceful stop signal
	/// is sent, Watchexec will wait for the command to exit. If it hasn't exited after this time,
	/// it is forcefully terminated.
	///
	/// Takes a unit-less value in seconds, or a time span value such as "5min 20s".
	/// Providing a unit-less value is deprecated and will warn; it will be an error in the future.
	///
	/// The default is 10 seconds. Set to 0 to immediately force-kill the command.
	///
	/// This has no practical effect on Windows as the command is always forcefully terminated; see
	/// '--stop-signal' for why.
	#[arg(
		long,
		default_value = "10s",
		hide_default_value = true,
		value_name = "TIMEOUT"
	)]
	pub stop_timeout: TimeSpan,

	/// Translate signals from the OS to signals to send to the command
	///
	/// Takes a pair of signal names, separated by a colon, such as "TERM:INT" to map SIGTERM to
	/// SIGINT. The first signal is the one received by watchexec, and the second is the one sent to
	/// the command. The second can be omitted to discard the first signal, such as "TERM:" to
	/// not do anything on SIGTERM.
	///
	/// If SIGINT or SIGTERM are mapped, then they no longer quit Watchexec. Besides making it hard
	/// to quit Watchexec itself, this is useful to send pass a Ctrl-C to the command without also
	/// terminating Watchexec and the underlying program with it, e.g. with "INT:INT".
	///
	/// This option can be specified multiple times to map multiple signals.
	///
	/// Signal syntax is case-insensitive for short names (like "TERM", "USR2") and long names (like
	/// "SIGKILL", "SIGHUP"). Signal numbers are also supported (like "15", "31"). On Windows, the
	/// forms "STOP", "CTRL+C", and "CTRL+BREAK" are also supported to receive, but Watchexec cannot
	/// yet deliver other "signals" than a STOP.
	#[arg(long = "map-signal", value_name = "SIGNAL:SIGNAL", value_parser = SignalMappingValueParser)]
	pub signal_map: Vec<SignalMapping>,

	/// Time to wait for new events before taking action
	///
	/// When an event is received, Watchexec will wait for up to this amount of time before handling
	/// it (such as running the command). This is essential as what you might perceive as a single
	/// change may actually emit many events, and without this behaviour, Watchexec would run much
	/// too often. Additionally, it's not infrequent that file writes are not atomic, and each write
	/// may emit an event, so this is a good way to avoid running a command while a file is
	/// partially written.
	///
	/// An alternative use is to set a high value (like "30min" or longer), to save power or
	/// bandwidth on intensive tasks, like an ad-hoc backup script. In those use cases, note that
	/// every accumulated event will build up in memory.
	///
	/// Takes a unit-less value in milliseconds, or a time span value such as "5sec 20ms".
	/// Providing a unit-less value is deprecated and will warn; it will be an error in the future.
	///
	/// The default is 50 milliseconds. Setting to 0 is highly discouraged.
	#[arg(
		long,
		short,
		default_value = "50ms",
		hide_default_value = true,
		value_name = "TIMEOUT"
	)]
	pub debounce: TimeSpan<1_000_000>,

	/// Exit when stdin closes
	///
	/// This watches the stdin file descriptor for EOF, and exits Watchexec gracefully when it is
	/// closed. This is used by some process managers to avoid leaving zombie processes around.
	#[arg(long)]
	pub stdin_quit: bool,

	/// Don't load gitignores
	///
	/// Among other VCS exclude files, like for Mercurial, Subversion, Bazaar, DARCS, Fossil. Note
	/// that Watchexec will detect which of these is in use, if any, and only load the relevant
	/// files. Both global (like '~/.gitignore') and local (like '.gitignore') files are considered.
	///
	/// This option is useful if you want to watch files that are ignored by Git.
	#[arg(
		long,
		help_heading = OPTSET_FILTERING,
	)]
	pub no_vcs_ignore: bool,

	/// Don't load project-local ignores
	///
	/// This disables loading of project-local ignore files, like '.gitignore' or '.ignore' in the
	/// watched project. This is contrasted with '--no-vcs-ignore', which disables loading of Git
	/// and other VCS ignore files, and with '--no-global-ignore', which disables loading of global
	/// or user ignore files, like '~/.gitignore' or '~/.config/watchexec/ignore'.
	///
	/// Supported project ignore files:
	///
	///   - Git: .gitignore at project root and child directories, .git/info/exclude, and the file pointed to by `core.excludesFile` in .git/config.
	///   - Mercurial: .hgignore at project root and child directories.
	///   - Bazaar: .bzrignore at project root.
	///   - Darcs: _darcs/prefs/boring
	///   - Fossil: .fossil-settings/ignore-glob
	///   - Ripgrep/Watchexec/generic: .ignore at project root and child directories.
	///
	/// VCS ignore files (Git, Mercurial, Bazaar, Darcs, Fossil) are only used if the corresponding
	/// VCS is discovered to be in use for the project/origin. For example, a .bzrignore in a Git
	/// repository will be discarded.
	#[arg(
		long,
		help_heading = OPTSET_FILTERING,
		verbatim_doc_comment,
	)]
	pub no_project_ignore: bool,

	/// Don't load global ignores
	///
	/// This disables loading of global or user ignore files, like '~/.gitignore',
	/// '~/.config/watchexec/ignore', or '%APPDATA%\Bazzar\2.0\ignore'. Contrast with
	/// '--no-vcs-ignore' and '--no-project-ignore'.
	///
	/// Supported global ignore files
	///
	///   - Git (if core.excludesFile is set): the file at that path
	///   - Git (otherwise): the first found of $XDG_CONFIG_HOME/git/ignore, %APPDATA%/.gitignore, %USERPROFILE%/.gitignore, $HOME/.config/git/ignore, $HOME/.gitignore.
	///   - Bazaar: the first found of %APPDATA%/Bazzar/2.0/ignore, $HOME/.bazaar/ignore.
	///   - Watchexec: the first found of $XDG_CONFIG_HOME/watchexec/ignore, %APPDATA%/watchexec/ignore, %USERPROFILE%/.watchexec/ignore, $HOME/.watchexec/ignore.
	///
	/// Like for project files, Git and Bazaar global files will only be used for the corresponding
	/// VCS as used in the project.
	#[arg(
		long,
		help_heading = OPTSET_FILTERING,
		verbatim_doc_comment,
	)]
	pub no_global_ignore: bool,

	/// Don't use internal default ignores
	///
	/// Watchexec has a set of default ignore patterns, such as editor swap files, `*.pyc`, `*.pyo`,
	/// `.DS_Store`, `.bzr`, `_darcs`, `.fossil-settings`, `.git`, `.hg`, `.pijul`, `.svn`, and
	/// Watchexec log files.
	#[arg(
		long,
		help_heading = OPTSET_FILTERING,
	)]
	pub no_default_ignore: bool,

	/// Don't discover ignore files at all
	///
	/// This is a shorthand for '--no-global-ignore', '--no-vcs-ignore', '--no-project-ignore', but
	/// even more efficient as it will skip all the ignore discovery mechanisms from the get go.
	///
	/// Note that default ignores are still loaded, see '--no-default-ignore'.
	#[arg(
		long,
		help_heading = OPTSET_FILTERING,
	)]
	pub no_discover_ignore: bool,

	/// Don't ignore anything at all
	///
	/// This is a shorthand for '--no-discover-ignore', '--no-default-ignore'.
	///
	/// Note that ignores explicitly loaded via other command line options, such as '--ignore' or
	/// '--ignore-file', will still be used.
	#[arg(
		long,
		help_heading = OPTSET_FILTERING,
	)]
	pub ignore_nothing: bool,

	/// Wait until first change before running command
	///
	/// By default, Watchexec will run the command once immediately. With this option, it will
	/// instead wait until an event is detected before running the command as normal.
	#[arg(long, short)]
	pub postpone: bool,

	/// Sleep before running the command
	///
	/// This option will cause Watchexec to sleep for the specified amount of time before running
	/// the command, after an event is detected. This is like using "sleep 5 && command" in a shell,
	/// but portable and slightly more efficient.
	///
	/// Takes a unit-less value in seconds, or a time span value such as "2min 5s".
	/// Providing a unit-less value is deprecated and will warn; it will be an error in the future.
	#[arg(long, value_name = "DURATION")]
	pub delay_run: Option<TimeSpan>,

	/// Poll for filesystem changes
	///
	/// By default, and where available, Watchexec uses the operating system's native file system
	/// watching capabilities. This option disables that and instead uses a polling mechanism, which
	/// is less efficient but can work around issues with some file systems (like network shares) or
	/// edge cases.
	///
	/// Optionally takes a unit-less value in milliseconds, or a time span value such as "2s 500ms",
	/// to use as the polling interval. If not specified, the default is 30 seconds.
	/// Providing a unit-less value is deprecated and will warn; it will be an error in the future.
	///
	/// Aliased as '--force-poll'.
	#[arg(
		long,
		alias = "force-poll",
		num_args = 0..=1,
		default_missing_value = "30s",
		value_name = "INTERVAL",
	)]
	pub poll: Option<TimeSpan<1_000_000>>,

	/// Use a different shell
	///
	/// By default, Watchexec will use '$SHELL' if it's defined or a default of 'sh' on Unix-likes,
	/// and either 'pwsh', 'powershell', or 'cmd' (CMD.EXE) on Windows, depending on what Watchexec
	/// detects is the running shell.
	///
	/// With this option, you can override that and use a different shell, for example one with more
	/// features or one which has your custom aliases and functions.
	///
	/// If the value has spaces, it is parsed as a command line, and the first word used as the
	/// shell program, with the rest as arguments to the shell.
	///
	/// The command is run with the '-c' flag (except for 'cmd' on Windows, where it's '/C').
	///
	/// The special value 'none' can be used to disable shell use entirely. In that case, the
	/// command provided to Watchexec will be parsed, with the first word being the executable and
	/// the rest being the arguments, and executed directly. Note that this parsing is rudimentary,
	/// and may not work as expected in all cases.
	///
	/// Using 'none' is a little more efficient and can enable a stricter interpretation of the
	/// input, but it also means that you can't use shell features like globbing, redirection,
	/// control flow, logic, or pipes.
	///
	/// Examples:
	///
	/// Use without shell:
	///
	///   $ watchexec -n -- zsh -x -o shwordsplit scr
	///
	/// Use with powershell core:
	///
	///   $ watchexec --shell=pwsh -- Test-Connection localhost
	///
	/// Use with CMD.exe:
	///
	///   $ watchexec --shell=cmd -- dir
	///
	/// Use with a different unix shell:
	///
	///   $ watchexec --shell=bash -- 'echo $BASH_VERSION'
	///
	/// Use with a unix shell and options:
	///
	///   $ watchexec --shell='zsh -x -o shwordsplit' -- scr
	#[arg(
		long,
		help_heading = OPTSET_COMMAND,
		value_name = "SHELL",
	)]
	pub shell: Option<String>,

	/// Shorthand for '--shell=none'
	#[arg(
		short = 'n',
		help_heading = OPTSET_COMMAND,
	)]
	pub no_shell: bool,

	/// Deprecated shorthand for '--emit-events=none'
	///
	/// This is the old way to disable event emission into the environment. See '--emit-events' for
	/// more. Will be removed at next major release.
	#[arg(
		long,
		help_heading = OPTSET_COMMAND,
		hide = true, // deprecated
	)]
	pub no_environment: bool,

	/// Configure event emission
	///
	/// Watchexec can emit event information when running a command, which can be used by the child
	/// process to target specific changed files.
	///
	/// One thing to take care with is assuming inherent behaviour where there is only chance.
	/// Notably, it could appear as if the `RENAMED` variable contains both the original and the new
	/// path being renamed. In previous versions, it would even appear on some platforms as if the
	/// original always came before the new. However, none of this was true. It's impossible to
	/// reliably and portably know which changed path is the old or new, "half" renames may appear
	/// (only the original, only the new), "unknown" renames may appear (change was a rename, but
	/// whether it was the old or new isn't known), rename events might split across two debouncing
	/// boundaries, and so on.
	///
	/// This option controls where that information is emitted. It defaults to 'none', which doesn't
	/// emit event information at all. The other options are 'environment' (deprecated), 'stdio',
	/// 'file', 'json-stdio', and 'json-file'.
	///
	/// The 'stdio' and 'file' modes are text-based: 'stdio' writes absolute paths to the stdin of
	/// the command, one per line, each prefixed with `create:`, `remove:`, `rename:`, `modify:`,
	/// or `other:`, then closes the handle; 'file' writes the same thing to a temporary file, and
	/// its path is given with the $WATCHEXEC_EVENTS_FILE environment variable.
	///
	/// There are also two JSON modes, which are based on JSON objects and can represent the full
	/// set of events Watchexec handles. Here's an example of a folder being created on Linux:
	///
	/// ```json
	///   {
	///     "tags": [
	///       {
	///         "kind": "path",
	///         "absolute": "/home/user/your/new-folder",
	///         "filetype": "dir"
	///       },
	///       {
	///         "kind": "fs",
	///         "simple": "create",
	///         "full": "Create(Folder)"
	///       },
	///       {
	///         "kind": "source",
	///         "source": "filesystem",
	///       }
	///     ],
	///     "metadata": {
	///       "notify-backend": "inotify"
	///     }
	///   }
	/// ```
	///
	/// The fields are as follows:
	///
	///   - `tags`, structured event data.
	///   - `tags[].kind`, which can be:
	///     * 'path', along with:
	///       + `absolute`, an absolute path.
	///       + `filetype`, a file type if known ('dir', 'file', 'symlink', 'other').
	///     * 'fs':
	///       + `simple`, the "simple" event type ('access', 'create', 'modify', 'remove', or 'other').
	///       + `full`, the "full" event type, which is too complex to fully describe here, but looks like 'General(Precise(Specific))'.
	///     * 'source', along with:
	///       + `source`, the source of the event ('filesystem', 'keyboard', 'mouse', 'os', 'time', 'internal').
	///     * 'keyboard', along with:
	///       + `keycode`. Currently only the value 'eof' is supported.
	///     * 'process', for events caused by processes:
	///       + `pid`, the process ID.
	///     * 'signal', for signals sent to Watchexec:
	///       + `signal`, the normalised signal name ('hangup', 'interrupt', 'quit', 'terminate', 'user1', 'user2').
	///     * 'completion', for when a command ends:
	///       + `disposition`, the exit disposition ('success', 'error', 'signal', 'stop', 'exception', 'continued').
	///       + `code`, the exit, signal, stop, or exception code.
	///   - `metadata`, additional information about the event.
	///
	/// The 'json-stdio' mode will emit JSON events to the standard input of the command, one per
	/// line, then close stdin. The 'json-file' mode will create a temporary file, write the
	/// events to it, and provide the path to the file with the $WATCHEXEC_EVENTS_FILE
	/// environment variable.
	///
	/// Finally, the 'environment' mode was the default until 2.0. It sets environment variables
	/// with the paths of the affected files, for filesystem events:
	///
	/// $WATCHEXEC_COMMON_PATH is set to the longest common path of all of the below variables,
	/// and so should be prepended to each path to obtain the full/real path. Then:
	///
	///   - $WATCHEXEC_CREATED_PATH is set when files/folders were created
	///   - $WATCHEXEC_REMOVED_PATH is set when files/folders were removed
	///   - $WATCHEXEC_RENAMED_PATH is set when files/folders were renamed
	///   - $WATCHEXEC_WRITTEN_PATH is set when files/folders were modified
	///   - $WATCHEXEC_META_CHANGED_PATH is set when files/folders' metadata were modified
	///   - $WATCHEXEC_OTHERWISE_CHANGED_PATH is set for every other kind of pathed event
	///
	/// Multiple paths are separated by the system path separator, ';' on Windows and ':' on unix.
	/// Within each variable, paths are deduplicated and sorted in binary order (i.e. neither
	/// Unicode nor locale aware).
	///
	/// This is the legacy mode, is deprecated, and will be removed in the future. The environment
	/// is a very restricted space, while also limited in what it can usefully represent. Large
	/// numbers of files will either cause the environment to be truncated, or may error or crash
	/// the process entirely. The $WATCHEXEC_COMMON_PATH is also unintuitive, as demonstrated by the
	/// multiple confused queries that have landed in my inbox over the years.
	#[arg(
		long,
		help_heading = OPTSET_COMMAND,
		verbatim_doc_comment,
		default_value = "none",
		hide_default_value = true,
		value_name = "MODE",
		required_if_eq("only_emit_events", "true"),
	)]
	pub emit_events_to: EmitEvents,

	/// Only emit events to stdout, run no commands.
	///
	/// This is a convenience option for using Watchexec as a file watcher, without running any
	/// commands. It is almost equivalent to using `cat` as the command, except that it will not
	/// spawn a new process for each event.
	///
	/// This option requires `--emit-events-to` to be set, and restricts the available modes to
	/// `stdio` and `json-stdio`, modifying their behaviour to write to stdout instead of the stdin
	/// of the command.
	#[arg(
		long,
		help_heading = OPTSET_OUTPUT,
		conflicts_with_all = ["command", "completions", "manual"],
	)]
	pub only_emit_events: bool,

	/// Add env vars to the command
	///
	/// This is a convenience option for setting environment variables for the command, without
	/// setting them for the Watchexec process itself.
	///
	/// Use key=value syntax. Multiple variables can be set by repeating the option.
	#[arg(
		long,
		short = 'E',
		help_heading = OPTSET_COMMAND,
		value_name = "KEY=VALUE",
	)]
	pub env: Vec<String>,

	/// Don't use a process group
	///
	/// By default, Watchexec will run the command in a process group, so that signals and
	/// terminations are sent to all processes in the group. Sometimes that's not what you want, and
	/// you can disable the behaviour with this option.
	///
	/// Deprecated, use '--wrap-process=none' instead.
	#[arg(
		long,
		help_heading = OPTSET_COMMAND,
	)]
	pub no_process_group: bool,

	/// Configure how the process is wrapped
	///
	/// By default, Watchexec will run the command in a process group in Unix, and in a Job Object
	/// in Windows.
	///
	/// Some Unix programs prefer running in a session, while others do not work in a process group.
	///
	/// Use 'group' to use a process group, 'session' to use a process session, and 'none' to run
	/// the command directly. On Windows, either of 'group' or 'session' will use a Job Object.
	#[arg(
		long,
		help_heading = OPTSET_COMMAND,
		value_name = "MODE",
		default_value = "group",
	)]
	pub wrap_process: WrapMode,

	/// Testing only: exit Watchexec after the first run
	#[arg(short = '1', hide = true)]
	pub once: bool,

	/// Alert when commands start and end
	///
	/// With this, Watchexec will emit a desktop notification when a command starts and ends, on
	/// supported platforms. On unsupported platforms, it may silently do nothing, or log a warning.
	#[arg(
		short = 'N',
		long,
		help_heading = OPTSET_OUTPUT,
	)]
	pub notify: bool,

	/// When to use terminal colours
	///
	/// Setting the environment variable `NO_COLOR` to any value is equivalent to `--color=never`.
	#[arg(
		long,
		help_heading = OPTSET_OUTPUT,
		default_value = "auto",
		value_name = "MODE",
		alias = "colour",
	)]
	pub color: ColourMode,

	/// Print how long the command took to run
	///
	/// This may not be exactly accurate, as it includes some overhead from Watchexec itself. Use
	/// the `time` utility, high-precision timers, or benchmarking tools for more accurate results.
	#[arg(
		long,
		help_heading = OPTSET_OUTPUT,
	)]
	pub timings: bool,

	/// Don't print starting and stopping messages
	///
	/// By default Watchexec will print a message when the command starts and stops. This option
	/// disables this behaviour, so only the command's output, warnings, and errors will be printed.
	#[arg(
		short,
		long,
		help_heading = OPTSET_OUTPUT,
	)]
	pub quiet: bool,

	/// Ring the terminal bell on command completion
	#[arg(
		long,
		help_heading = OPTSET_OUTPUT,
	)]
	pub bell: bool,

	/// Set the project origin
	///
	/// Watchexec will attempt to discover the project's "origin" (or "root") by searching for a
	/// variety of markers, like files or directory patterns. It does its best but sometimes gets it
	/// it wrong, and you can override that with this option.
	///
	/// The project origin is used to determine the path of certain ignore files, which VCS is being
	/// used, the meaning of a leading '/' in filtering patterns, and maybe more in the future.
	///
	/// When set, Watchexec will also not bother searching, which can be significantly faster.
	#[arg(
		long,
		value_hint = ValueHint::DirPath,
		value_name = "DIRECTORY",
	)]
	pub project_origin: Option<PathBuf>,

	/// Set the working directory
	///
	/// By default, the working directory of the command is the working directory of Watchexec. You
	/// can change that with this option. Note that paths may be less intuitive to use with this.
	#[arg(
		long,
		value_hint = ValueHint::DirPath,
		value_name = "DIRECTORY",
	)]
	pub workdir: Option<PathBuf>,

	/// Filename extensions to filter to
	///
	/// This is a quick filter to only emit events for files with the given extensions. Extensions
	/// can be given with or without the leading dot (e.g. 'js' or '.js'). Multiple extensions can
	/// be given by repeating the option or by separating them with commas.
	#[arg(
		long = "exts",
		short = 'e',
		help_heading = OPTSET_FILTERING,
		value_delimiter = ',',
		value_name = "EXTENSIONS",
	)]
	pub filter_extensions: Vec<String>,

	/// Filename patterns to filter to
	///
	/// Provide a glob-like filter pattern, and only events for files matching the pattern will be
	/// emitted. Multiple patterns can be given by repeating the option. Events that are not from
	/// files (e.g. signals, keyboard events) will pass through untouched.
	#[arg(
		long = "filter",
		short = 'f',
		help_heading = OPTSET_FILTERING,
		value_name = "PATTERN",
	)]
	pub filter_patterns: Vec<String>,

	/// Files to load filters from
	///
	/// Provide a path to a file containing filters, one per line. Empty lines and lines starting
	/// with '#' are ignored. Uses the same pattern format as the '--filter' option.
	///
	/// This can also be used via the $WATCHEXEC_FILTER_FILES environment variable.
	#[arg(
		long = "filter-file",
		help_heading = OPTSET_FILTERING,
		value_delimiter = PATH_SEPARATOR.chars().next().unwrap(),
		value_hint = ValueHint::FilePath,
		value_name = "PATH",
		env = "WATCHEXEC_FILTER_FILES",
		hide_env = true,
	)]
	pub filter_files: Vec<PathBuf>,

	/// [experimental] Filter programs.
	///
	/// /!\ This option is EXPERIMENTAL and may change and/or vanish without notice.
	///
	/// Provide your own custom filter programs in jaq (similar to jq) syntax. Programs are given
	/// an event in the same format as described in '--emit-events-to' and must return a boolean.
	/// Invalid programs will make watchexec fail to start; use '-v' to see program runtime errors.
	///
	/// In addition to the jaq stdlib, watchexec adds some custom filter definitions:
	///
	///   - 'path | file_meta' returns file metadata or null if the file does not exist.
	///
	///   - 'path | file_size' returns the size of the file at path, or null if it does not exist.
	///
	///   - 'path | file_read(bytes)' returns a string with the first n bytes of the file at path.
	///     If the file is smaller than n bytes, the whole file is returned. There is no filter to
	///     read the whole file at once to encourage limiting the amount of data read and processed.
	///
	///   - 'string | hash', and 'path | file_hash' return the hash of the string or file at path.
	///     No guarantee is made about the algorithm used: treat it as an opaque value.
	///
	///   - 'any | kv_store(key)', 'kv_fetch(key)', and 'kv_clear' provide a simple key-value store.
	///     Data is kept in memory only, there is no persistence. Consistency is not guaranteed.
	///
	///   - 'any | printout', 'any | printerr', and 'any | log(level)' will print or log any given
	///     value to stdout, stderr, or the log (levels = error, warn, info, debug, trace), and
	///     pass the value through (so '[1] | log("debug") | .[]' will produce a '1' and log '[1]').
	///
	/// All filtering done with such programs, and especially those using kv or filesystem access,
	/// is much slower than the other filtering methods. If filtering is too slow, events will back
	/// up and stall watchexec. Take care when designing your filters.
	///
	/// If the argument to this option starts with an '@', the rest of the argument is taken to be
	/// the path to a file containing a jaq program.
	///
	/// Jaq programs are run in order, after all other filters, and short-circuit: if a filter (jaq
	/// or not) rejects an event, execution stops there, and no other filters are run. Additionally,
	/// they stop after outputting the first value, so you'll want to use 'any' or 'all' when
	/// iterating, otherwise only the first item will be processed, which can be quite confusing!
	///
	/// Find user-contributed programs or submit your own useful ones at
	/// <https://github.com/watchexec/watchexec/discussions/592>.
	///
	/// ## Examples:
	///
	/// Regexp ignore filter on paths:
	///
	///   'all(.tags[] | select(.kind == "path"); .absolute | test("[.]test[.]js$")) | not'
	///
	/// Pass any event that creates a file:
	///
	///   'any(.tags[] | select(.kind == "fs"); .simple == "create")'
	///
	/// Pass events that touch executable files:
	///
	///   'any(.tags[] | select(.kind == "path" && .filetype == "file"); .absolute | metadata | .executable)'
	///
	/// Ignore files that start with shebangs:
	///
	///   'any(.tags[] | select(.kind == "path" && .filetype == "file"); .absolute | read(2) == "#!") | not'
	#[arg(
		long = "filter-prog",
		short = 'j',
		help_heading = OPTSET_FILTERING,
		value_name = "EXPRESSION",
	)]
	pub filter_programs: Vec<String>,

	#[doc(hidden)]
	#[clap(skip)]
	pub filter_programs_parsed: Vec<jaq_syn::Main>,

	/// Filename patterns to filter out
	///
	/// Provide a glob-like filter pattern, and events for files matching the pattern will be
	/// excluded. Multiple patterns can be given by repeating the option. Events that are not from
	/// files (e.g. signals, keyboard events) will pass through untouched.
	#[arg(
		long = "ignore",
		short = 'i',
		help_heading = OPTSET_FILTERING,
		value_name = "PATTERN",
	)]
	pub ignore_patterns: Vec<String>,

	/// Files to load ignores from
	///
	/// Provide a path to a file containing ignores, one per line. Empty lines and lines starting
	/// with '#' are ignored. Uses the same pattern format as the '--ignore' option.
	///
	/// This can also be used via the $WATCHEXEC_IGNORE_FILES environment variable.
	#[arg(
		long = "ignore-file",
		help_heading = OPTSET_FILTERING,
		value_delimiter = PATH_SEPARATOR.chars().next().unwrap(),
		value_hint = ValueHint::FilePath,
		value_name = "PATH",
		env = "WATCHEXEC_IGNORE_FILES",
		hide_env = true,
	)]
	pub ignore_files: Vec<PathBuf>,

	/// Filesystem events to filter to
	///
	/// This is a quick filter to only emit events for the given types of filesystem changes. Choose
	/// from 'access', 'create', 'remove', 'rename', 'modify', 'metadata'. Multiple types can be
	/// given by repeating the option or by separating them with commas. By default, this is all
	/// types except for 'access'.
	///
	/// This may apply filtering at the kernel level when possible, which can be more efficient, but
	/// may be more confusing when reading the logs.
	#[arg(
		long = "fs-events",
		help_heading = OPTSET_FILTERING,
		default_value = "create,remove,rename,modify,metadata",
		value_delimiter = ',',
		hide_default_value = true,
		value_name = "EVENTS",
	)]
	pub filter_fs_events: Vec<FsEvent>,

	/// Don't emit fs events for metadata changes
	///
	/// This is a shorthand for '--fs-events create,remove,rename,modify'. Using it alongside the
	/// '--fs-events' option is non-sensical and not allowed.
	#[arg(
		long = "no-meta",
		help_heading = OPTSET_FILTERING,
		conflicts_with = "filter_fs_events",
	)]
	pub filter_fs_meta: bool,

	/// Print events that trigger actions
	///
	/// This prints the events that triggered the action when handling it (after debouncing), in a
	/// human readable form. This is useful for debugging filters.
	///
	/// Use '-vvv' instead when you need more diagnostic information.
	#[arg(
		long,
		help_heading = OPTSET_DEBUGGING,
	)]
	pub print_events: bool,

	/// Show the manual page
	///
	/// This shows the manual page for Watchexec, if the output is a terminal and the 'man' program
	/// is available. If not, the manual page is printed to stdout in ROFF format (suitable for
	/// writing to a watchexec.1 file).
	#[arg(
		long,
		help_heading = OPTSET_DEBUGGING,
		conflicts_with_all = ["command", "completions"],
	)]
	pub manual: bool,

	/// Generate a shell completions script
	///
	/// Provides a completions script or configuration for the given shell. If Watchexec is not
	/// distributed with pre-generated completions, you can use this to generate them yourself.
	///
	/// Supported shells: bash, elvish, fish, nu, powershell, zsh.
	#[arg(
		long,
		help_heading = OPTSET_DEBUGGING,
		conflicts_with_all = ["command", "manual"],
	)]
	pub completions: Option<ShellCompletion>,

	#[command(flatten)]
	pub logging: logging::LoggingArgs,
}

#[derive(Clone, Copy, Debug, Default, ValueEnum)]
pub enum EmitEvents {
	#[default]
	Environment,
	Stdio,
	File,
	JsonStdio,
	JsonFile,
	None,
}

#[derive(Clone, Copy, Debug, Default, ValueEnum)]
pub enum OnBusyUpdate {
	#[default]
	Queue,
	DoNothing,
	Restart,
	Signal,
}

#[derive(Clone, Copy, Debug, Default, ValueEnum)]
pub enum WrapMode {
	#[default]
	Group,
	Session,
	None,
}

#[derive(Clone, Copy, Debug, Default, ValueEnum)]
pub enum ClearMode {
	#[default]
	Clear,
	Reset,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq, ValueEnum)]
pub enum FsEvent {
	Access,
	Create,
	Remove,
	Rename,
	Modify,
	Metadata,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq, ValueEnum)]
pub enum ShellCompletion {
	Bash,
	Elvish,
	Fish,
	Nu,
	Powershell,
	Zsh,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq, ValueEnum)]
pub enum ColourMode {
	Auto,
	Always,
	Never,
}

#[derive(Clone, Copy, Debug)]
pub struct TimeSpan<const UNITLESS_NANOS_MULTIPLIER: u64 = { 1_000_000_000 }>(pub Duration);

impl<const UNITLESS_NANOS_MULTIPLIER: u64> FromStr for TimeSpan<UNITLESS_NANOS_MULTIPLIER> {
	type Err = humantime::DurationError;

	fn from_str(s: &str) -> Result<Self, Self::Err> {
		s.parse::<u64>()
			.map_or_else(
				|_| humantime::parse_duration(s),
				|unitless| {
					eprintln!("Warning: unitless time span values are deprecated and will be removed in an upcoming version");
					Ok(Duration::from_nanos(unitless * UNITLESS_NANOS_MULTIPLIER))
				},
			)
			.map(TimeSpan)
	}
}

#[derive(Clone, Copy, Debug)]
pub struct SignalMapping {
	pub from: Signal,
	pub to: Option<Signal>,
}

#[derive(Clone)]
struct SignalMappingValueParser;

impl TypedValueParser for SignalMappingValueParser {
	type Value = SignalMapping;

	fn parse_ref(
		&self,
		_cmd: &Command,
		_arg: Option<&Arg>,
		value: &OsStr,
	) -> Result<Self::Value, clap::error::Error> {
		let value = value
			.to_str()
			.ok_or_else(|| clap::error::Error::raw(ErrorKind::ValueValidation, "invalid UTF-8"))?;
		let (from, to) = value
			.split_once(':')
			.ok_or_else(|| clap::error::Error::raw(ErrorKind::ValueValidation, "missing ':'"))?;

		let from = from
			.parse::<Signal>()
			.map_err(|sigparse| clap::error::Error::raw(ErrorKind::ValueValidation, sigparse))?;
		let to = if to.is_empty() {
			None
		} else {
			Some(to.parse::<Signal>().map_err(|sigparse| {
				clap::error::Error::raw(ErrorKind::ValueValidation, sigparse)
			})?)
		};

		Ok(Self::Value { from, to })
	}
}

fn expand_args_up_to_doubledash() -> Result<Vec<OsString>, std::io::Error> {
	use argfile::Argument;
	use std::collections::VecDeque;

	let args = std::env::args_os();
	let mut expanded_args = Vec::with_capacity(args.size_hint().0);

	let mut todo: VecDeque<_> = args.map(|a| Argument::parse(a, argfile::PREFIX)).collect();
	while let Some(next) = todo.pop_front() {
		match next {
			Argument::PassThrough(arg) => {
				expanded_args.push(arg.clone());
				if arg == "--" {
					break;
				}
			}
			Argument::Path(path) => {
				let content = std::fs::read_to_string(path)?;
				let new_args = argfile::parse_fromfile(&content, argfile::PREFIX);
				todo.reserve(new_args.len());
				for (i, arg) in new_args.into_iter().enumerate() {
					todo.insert(i, arg);
				}
			}
		}
	}

	while let Some(next) = todo.pop_front() {
		expanded_args.push(match next {
			Argument::PassThrough(arg) => arg,
			Argument::Path(path) => {
				let path = path.as_os_str();
				let mut restored = OsString::with_capacity(path.len() + 1);
				restored.push(OsStr::new("@"));
				restored.push(path);
				restored
			}
		});
	}
	Ok(expanded_args)
}

#[inline]
pub async fn get_args() -> Result<(Args, Option<WorkerGuard>)> {
	let prearg_logs = logging::preargs();
	if prearg_logs {
		warn!("⚠ RUST_LOG environment variable set or hardcoded, logging options have no effect");
	}

	debug!("expanding @argfile arguments if any");
	let args = expand_args_up_to_doubledash().expect("while expanding @argfile");

	debug!("parsing arguments");
	let mut args = Args::parse_from(args);

	let log_guard = if !prearg_logs {
		logging::postargs(&args.logging).await?
	} else {
		None
	};

	// https://no-color.org/
	if args.color == ColourMode::Auto && std::env::var("NO_COLOR").is_ok() {
		args.color = ColourMode::Never;
	}

	if args.ignore_nothing {
		args.no_global_ignore = true;
		args.no_vcs_ignore = true;
		args.no_project_ignore = true;
		args.no_default_ignore = true;
		args.no_discover_ignore = true;
	}

	if args.signal.is_some() {
		args.on_busy_update = OnBusyUpdate::Signal;
	} else if args.restart {
		args.on_busy_update = OnBusyUpdate::Restart;
	}

	if args.no_environment {
		warn!("--no-environment is deprecated");
		args.emit_events_to = EmitEvents::None;
	}

	if args.no_process_group {
		warn!("--no-process-group is deprecated");
		args.wrap_process = WrapMode::None;
	}

	if args.filter_fs_meta {
		args.filter_fs_events = vec![
			FsEvent::Create,
			FsEvent::Remove,
			FsEvent::Rename,
			FsEvent::Modify,
		];
	}

	if args.only_emit_events
		&& !matches!(
			args.emit_events_to,
			EmitEvents::JsonStdio | EmitEvents::Stdio
		) {
		Args::command()
			.error(
				ErrorKind::InvalidValue,
				"only-emit-events requires --emit-events-to=stdio or --emit-events-to=json-stdio",
			)
			.exit();
	}

	let workdir = if let Some(w) = take(&mut args.workdir) {
		w
	} else {
		let curdir = std::env::current_dir().into_diagnostic()?;
		canonicalize(curdir).into_diagnostic()?
	};
	info!(path=?workdir, "effective working directory");
	args.workdir = Some(workdir.clone());

	let project_origin = if let Some(p) = take(&mut args.project_origin) {
		p
	} else {
		crate::dirs::project_origin(&args).await?
	};
	info!(path=?project_origin, "effective project origin");
	args.project_origin = Some(project_origin.clone());

	args.paths = take(&mut args.recursive_paths)
		.into_iter()
		.map(|path| {
			{
				if path.is_absolute() {
					Ok(path)
				} else {
					canonicalize(project_origin.join(path)).into_diagnostic()
				}
			}
			.map(WatchedPath::non_recursive)
		})
		.chain(take(&mut args.non_recursive_paths).into_iter().map(|path| {
			{
				if path.is_absolute() {
					Ok(path)
				} else {
					canonicalize(project_origin.join(path)).into_diagnostic()
				}
			}
			.map(WatchedPath::non_recursive)
		}))
		.collect::<Result<BTreeSet<_>>>()?
		.into_iter()
		.collect();

	if args.paths.len() == 1
		&& args
			.paths
			.first()
			.map_or(false, |p| p.as_ref() == Path::new("/dev/null"))
	{
		info!("only path is /dev/null, not watching anything");
		args.paths = Vec::new();
	} else if args.paths.is_empty() {
		info!("no paths, using current directory");
		args.paths.push(args.workdir.clone().unwrap().into());
	}
	info!(paths=?args.paths, "effective watched paths");

	for (n, prog) in args.filter_programs.iter_mut().enumerate() {
		if let Some(progpath) = prog.strip_prefix('@') {
			trace!(?n, path=?progpath, "reading filter program from file");
			let mut progfile = File::open(&progpath).await.into_diagnostic()?;
			let mut buf =
				String::with_capacity(progfile.metadata().await.into_diagnostic()?.len() as _);
			let bytes_read = progfile.read_to_string(&mut buf).await.into_diagnostic()?;
			debug!(?n, path=?progpath, %bytes_read, "read filter program from file");
			*prog = buf;
		}
	}

	args.filter_programs_parsed = take(&mut args.filter_programs)
		.into_iter()
		.enumerate()
		.map(parse_filter_program)
		.collect::<Result<_, _>>()?;

	debug_assert!(args.workdir.is_some());
	debug_assert!(args.project_origin.is_some());
	info!(?args, "got arguments");
	Ok((args, log_guard))
}