package stdlib
import (
"fmt"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/convert"
"github.com/zclconf/go-cty/cty/function"
)
var ConcatFunc = function.New(&function.Spec{
Params: []function.Parameter{},
VarParam: &function.Parameter{
Name: "seqs",
Type: cty.DynamicPseudoType,
},
Type: func(args []cty.Value) (ret cty.Type, err error) {
if len(args) == 0 {
return cty.NilType, fmt.Errorf("at least one argument is required")
}
if args[0].Type().IsListType() {
// Possibly we're going to return a list, if all of our other
// args are also lists and we can find a common element type.
tys := make([]cty.Type, len(args))
for i, val := range args {
ty := val.Type()
if !ty.IsListType() {
tys = nil
break
}
tys[i] = ty
}
if tys != nil {
commonType, _ := convert.UnifyUnsafe(tys)
if commonType != cty.NilType {
return commonType, nil
}
}
}
etys := make([]cty.Type, 0, len(args))
for i, val := range args {
ety := val.Type()
switch {
case ety.IsTupleType():
etys = append(etys, ety.TupleElementTypes()...)
case ety.IsListType():
if !val.IsKnown() {
// We need to know the list to count its elements to
// build our tuple type, so any concat of an unknown
// list can't be typed yet.
return cty.DynamicPseudoType, nil
}
l := val.LengthInt()
subEty := ety.ElementType()
for j := 0; j < l; j++ {
etys = append(etys, subEty)
}
default:
return cty.NilType, function.NewArgErrorf(
i, "all arguments must be lists or tuples; got %s",
ety.FriendlyName(),
)
}
}
return cty.Tuple(etys), nil
},
Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
switch {
case retType.IsListType():
// If retType is a list type then we know that all of the
// given values will be lists and that they will either be of
// retType or of something we can convert to retType.
vals := make([]cty.Value, 0, len(args))
for i, list := range args {
list, err = convert.Convert(list, retType)
if err != nil {
// Conversion might fail because we used UnifyUnsafe
// to choose our return type.
return cty.NilVal, function.NewArgError(i, err)
}
it := list.ElementIterator()
for it.Next() {
_, v := it.Element()
vals = append(vals, v)
}
}
if len(vals) == 0 {
return cty.ListValEmpty(retType.ElementType()), nil
}
return cty.ListVal(vals), nil
case retType.IsTupleType():
// If retType is a tuple type then we could have a mixture of
// lists and tuples but we know they all have known values
// (because our params don't AllowUnknown) and we know that
// concatenating them all together will produce a tuple of
// retType because of the work we did in the Type function above.
vals := make([]cty.Value, 0, len(args))
for _, seq := range args {
// Both lists and tuples support ElementIterator, so this is easy.
it := seq.ElementIterator()
for it.Next() {
_, v := it.Element()
vals = append(vals, v)
}
}
return cty.TupleVal(vals), nil
default:
// should never happen if Type is working correctly above
panic("unsupported return type")
}
},
})
var RangeFunc = function.New(&function.Spec{
VarParam: &function.Parameter{
Name: "params",
Type: cty.Number,
},
Type: function.StaticReturnType(cty.List(cty.Number)),
Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
var start, end, step cty.Value
switch len(args) {
case 1:
if args[0].LessThan(cty.Zero).True() {
start, end, step = cty.Zero, args[0], cty.NumberIntVal(-1)
} else {
start, end, step = cty.Zero, args[0], cty.NumberIntVal(1)
}
case 2:
if args[1].LessThan(args[0]).True() {
start, end, step = args[0], args[1], cty.NumberIntVal(-1)
} else {
start, end, step = args[0], args[1], cty.NumberIntVal(1)
}
case 3:
start, end, step = args[0], args[1], args[2]
default:
return cty.NilVal, fmt.Errorf("must have one, two, or three arguments")
}
var vals []cty.Value
if step == cty.Zero {
return cty.NilVal, function.NewArgErrorf(2, "step must not be zero")
}
down := step.LessThan(cty.Zero).True()
if down {
if end.GreaterThan(start).True() {
return cty.NilVal, function.NewArgErrorf(1, "end must be less than start when step is negative")
}
} else {
if end.LessThan(start).True() {
return cty.NilVal, function.NewArgErrorf(1, "end must be greater than start when step is positive")
}
}
num := start
for {
if down {
if num.LessThanOrEqualTo(end).True() {
break
}
} else {
if num.GreaterThanOrEqualTo(end).True() {
break
}
}
if len(vals) >= 1024 {
// Artificial limit to prevent bad arguments from consuming huge amounts of memory
return cty.NilVal, fmt.Errorf("more than 1024 values were generated; either decrease the difference between start and end or use a smaller step")
}
vals = append(vals, num)
num = num.Add(step)
}
if len(vals) == 0 {
return cty.ListValEmpty(cty.Number), nil
}
return cty.ListVal(vals), nil
},
})
// Concat takes one or more sequences (lists or tuples) and returns the single
// sequence that results from concatenating them together in order.
//
// If all of the given sequences are lists of the same element type then the
// result is a list of that type. Otherwise, the result is a of a tuple type
// constructed from the given sequence types.
func Concat(seqs ...cty.Value) (cty.Value, error) {
return ConcatFunc.Call(seqs)
}
// Range creates a list of numbers by starting from the given starting value,
// then adding the given step value until the result is greater than or
// equal to the given stopping value. Each intermediate result becomes an
// element in the resulting list.
//
// When all three parameters are set, the order is (start, end, step). If
// only two parameters are set, they are the start and end respectively and
// step defaults to 1. If only one argument is set, it gives the end value
// with start defaulting to 0 and step defaulting to 1.
//
// Because the resulting list must be fully buffered in memory, there is an
// artificial cap of 1024 elements, after which this function will return
// an error to avoid consuming unbounded amounts of memory. The Range function
// is primarily intended for creating small lists of indices to iterate over,
// so there should be no reason to generate huge lists with it.
func Range(params ...cty.Value) (cty.Value, error) {
return RangeFunc.Call(params)
}
