expr

type Binding interface {
	Evaluator
	cli.Lookup

	// Expr retrieves the expression operator if it is available
	Expr() *Expr
}

type Evaluator interface {
	// Evaluate performs the evaluation.  The v argument is the value of the prior
	// expression operator.  The yield argument is used to pass one or more additional
	// values to the next expression operator.
	Evaluate(c context.Context, v any, yield func(any) error) error
}

type EvaluatorFunc func(*cli.Context, any, func(any) error) error

type Expr struct {
	// Name provides the name of the expression operator. This value must be set, and it is used to access
	// the expression operator's value via the context
	Name string

	// Aliases provides a list of alternative names for the expression operator.  In general, Name should
	// be used for the long name of the expression operator, and Aliases should contain the short name.
	// If there are additional names for compatibility reasons, they should be included
	// with Aliases but listed after the preferred names. Note that only one short name
	// and one long name is displayed on help screens by default.
	Aliases []string

	// Args contains each of the arguments that are processed for the expression operators.  Expression
	// operators don't contain values directly; they process one or more arguments.
	Args []*cli.Arg

	// HelpText contains text which briefly describes the usage of the expression operator.
	// For style, generally the usage text should be limited to about 40 characters.
	// Sentence case is recommended for the usage text.    Uppercase is recommended for the
	// text of placeholders.  The placeholder is used in the synopsis for the expression operator as well
	// as error messages.
	HelpText string

	// ManualText provides the text shown in the manual.  The default templates don't use this value
	ManualText string

	// UsageText provides the usage for the expression operator.  If left blank, a succinct synopsis
	// is generated from the type of the expression operator's arguments
	UsageText string

	// Category specifies the expression operator category.  When categories are used, operators are grouped
	// together on the help screen
	Category string

	// Description provides a long description.  The long description is
	// not used in any templates by default.  The type of Description should be string or
	// fmt.Stringer.  Refer to func Description for details.
	Description any

	// Evaluate provides the evaluation behavior for the expression.  The value should
	// implement Evaluator or support runtime conversion to that interface via
	// the rules provided by the cli.EvaluatorOf function.
	Evaluate any

	// Before executes before the expression is evaluated.  Refer to cli.Action about the correct
	// function signature to use.
	Before any

	// After executes after the expression is evaluated.  Refer to cli.Action about the correct
	// function signature to use.
	After any

	// Uses provides an action handler that is always executed during the initialization phase
	// of the app.  Typically, hooks and other configuration actions are added to this handler.
	Uses any

	// Data provides an arbitrary mapping of additional data.  This data can be used by
	// middleware and it is made available to templates
	Data map[string]any

	// Options sets various options about how to treat the expression operator.  For example, options can
	// hide the expression operator.
	Options cli.Option
	// contains filtered or unexported fields
}

type Expression struct {

	// Exprs identifies the expression operators that are allowed
	Exprs []*Expr
	// contains filtered or unexported fields
}

type Invariant bool

type Predicate func(v any) bool

type Yielder func(any) error