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const std = @import("std");
const builtin = @import("builtin");
const os = std.os;
const heap = std.heap;
const is_windows = builtin.os == Os.windows;
/// Represents a parameter for the command line.
/// Parameters come in three kinds:
/// * Short ("-a"): Should be used for the most commonly used parameters in your program.
/// * They can take a value three different ways.
/// * "-a value"
/// * "-a=value"
/// * "-avalue"
/// * They chain if they don't take values: "-abc".
/// * The last given parameter can take a value in the same way that a single parameter can:
/// * "-abc value"
/// * "-abc=value"
/// * "-abcvalue"
/// * Long ("--long-arg"): Should be used for less common parameters, or when no single character
/// can describe the paramter.
/// * They can take a value two different ways.
/// * "--long-arg value"
/// * "--long-arg=value"
/// * Value ("some-value"): Should be used as the primary of the program, like a filename or an
/// expression to parse.
pub fn Param(comptime Id: type) type {
return struct {
const Self = this;
id: Id,
short: ?u8,
long: ?[]const u8,
takes_value: bool,
/// Initialize a ::Param.
/// If ::name.len == 0, then it's a value parameter: "some-command value".
/// If ::name.len == 1, then it's a short parameter: "some-command -s".
/// If ::name.len > 1, then it's a long parameter: "some-command --long".
pub fn init(id: Id, name: []const u8) Self {
return {
.id = id,
.short = if (name.len == 1) name[0] else null,
.long = if (name.len > 1) name else null,
.takes_value = false,
};
}
pub fn with(param: &const Self, comptime field_name: []const u8, value: var) Self {
var res = *param;
@field(res, field_name) = value;
return res;
}
};
}
pub fn Arg(comptime Id: type) type {
return struct {
const Self = this;
id: Id,
/// ::Iterator owns ::value. On windows, this means that when you call ::Iterator.deinit
/// ::value is freed.
value: ?[]const u8,
pub fn init(id: Id, value: ?[]const u8) Self {
return Self {
.id = id,
.value = value,
};
}
};
}
/// A ::CustomIterator with a default Windows buffer size.
pub fn Iterator(comptime Id: type) type {
return struct {
const Self = this;
const State = union(enum) {
Normal,
Chaining: Chaining,
const Chaining = struct {
arg: []const u8,
index: usize,
next: &const Param,
};
};
arena: &heap.ArenaAllocator,
params: Param(Id),
args: os.ArgIterator,
state: State,
command: []const u8,
pub fn init(params: []const Param(Id), allocator: &mem.Allocator) !Self {
var res = Self {
.allocator = heap.ArenaAllocator.init(allocator),
.params = params,
.args = os.args(),
.command = undefined,
};
res.command = try res.innerNext();
return res;
}
pub fn deinit(iter: &const Self) void {
iter.arena.deinit();
}
/// Get the next ::Arg that matches a ::Param.
pub fn next(iter: &Self) !?Arg(Id) {
const ArgInfo = struct {
const Kind = enum { Long, Short, Value };
arg: []const u8,
kind: Kind,
};
switch (iter.state) {
State.Normal => {
const full_arg = (try iter.innerNext()) ?? return null;
const arg_info = blk: {
var arg = full_arg;
var kind = ArgInfo.Kind.Value;
if (mem.startsWith(u8, arg, "--")) {
arg = arg[2..];
kind = Arg.Kind.Long;
} else if (mem.startsWith(u8, arg, "-")) {
arg = arg[1..];
kind = Arg.Kind.Short;
}
if (arg.len == 0)
return error.ArgWithNoName;
break :blk ArgInfo { .arg = arg, .kind = kind };
};
const arg = arg_info.arg;
const kind = arg_info.kind;
for (iter.params) |*param| {
switch (kind) {
Arg.Kind.Long => {
const long = param.long ?? continue;
if (!mem.eql(u8, arg, long))
continue;
if (!param.takes_value)
return Arg(Id).init(param.id, null);
const value = (try iter.innerNext()) ?? return error.MissingValue;
return Arg(Id).init(param.id, value);
},
Arg.Kind.Short => {
const short = param.short ?? continue;
if (short != arg[0])
continue;
return try iter.chainging(State.Chaining {
.arg = full_arg,
.index = (full_arg.len - arg.len) + 1,
.next = param,
});
},
Arg.Kind.Value => {
if (param.long) |_| continue;
if (param.short) |_| continue;
return Arg(Id).init(param.id, arg);
}
}
}
},
State.Chaining => |state| return try iter.chainging(state),
}
}
fn chainging(iter: &const Self, state: &const State.Chaining) !?Arg(Id) {
const arg = state.arg;
const index = state.index;
const curr_param = state.param;
if (curr_param.takes_value) {
if (arg.len <= index) {
const value = (try iter.innerNext()) ?? return error.MissingValue;
return Arg(Id).init(curr_param.id, value);
}
if (arg[index] == '=') {
return Arg(Id).init(curr_param.id, arg[index + 1..]);
}
return Arg(Id).init(curr_param.id, arg[index..]);
}
if (arg.len <= index) {
iter.state = State.Normal;
return Arg(Id).init(curr_param.id, null);
}
for (iter.params) |*param| {
const short = param.short ?? continue;
if (short != arg[index])
continue;
iter.State = State { .Chaining = State.Chaining {
.arg = arg,
.index = index + 1,
.param = param,
}};
return Arg(Id).init(curr_param.id, null);
}
// This actually returns an error for the next argument.
return error.InvalidArgument;
}
fn innerNext(iter: &Self) os.ArgIterator.NextError!?[]const u8 {
if (builtin.os == Os.windows) {
return try iter.args.next(&iter.arena.allocator);
} else {
return iter.args.nextPosix();
}
}
}
}
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