add prototype truncate function

Author: mschuchard

stdlib/number/truncate.go

@@ -0,0 +1,78 @@
+package numberfunc
+
+import (
+	"context"
+	"math"
+	"math/big"
+
+	"github.com/hashicorp/terraform-plugin-framework/function"
+	"github.com/hashicorp/terraform-plugin-log/tflog"
+)
+
+// ensure the implementation satisfies the expected interfaces
+var _ function.Function = &truncateFunction{}
+
+// helper pseudo-constructor to simplify provider server and testing implementation
+func NewTruncateFunction() function.Function {
+	return &truncateFunction{}
+}
+
+// function implementation
+type truncateFunction struct{}
+
+// function metadata
+func (*truncateFunction) Metadata(_ context.Context, req function.MetadataRequest, resp *function.MetadataResponse) {
+	resp.Name = "truncate"
+}
+
+// define the provider-level definition for the function
+func (*truncateFunction) Definition(_ context.Context, _ function.DefinitionRequest, resp *function.DefinitionResponse) {
+	resp.Definition = function.Definition{
+		Summary:             "Determine integer value of a number",
+		MarkdownDescription: "Return the integer value of an input parameter.",
+		Parameters: []function.Parameter{
+			function.NumberParameter{
+				Name:        "number",
+				Description: "Input number parameter for determining the truncated integer value.",
+			},
+		},
+		Return: function.Int64Return{},
+	}
+}
+
+func (*truncateFunction) Run(ctx context.Context, req function.RunRequest, resp *function.RunResponse) {
+	// initialize input parameters
+	var inputNum *big.Float
+
+	resp.Error = req.Arguments.Get(ctx, &inputNum)
+	if resp.Error != nil {
+		return
+	}
+
+	ctx = tflog.SetField(ctx, "truncate: number", inputNum)
+
+	// convert to float64
+	float, _ := inputNum.Float64()
+	if math.IsNaN(float) || math.IsInf(float, 0) {
+		resp.Error = function.NewArgumentFuncError(0, "truncate: input number is beyond the limits of float64")
+		return
+	}
+
+	// determine the truncated integer
+	truncate := math.Trunc(float)
+	if truncate > float64(math.MaxInt64) || truncate < float64(math.MinInt64) {
+		resp.Error = function.NewArgumentFuncError(0, "truncate: truncated input number is beyond the limits of int64")
+		return
+	}
+	result := int64(truncate)
+
+	ctx = tflog.SetField(ctx, "truncate: truncated", result)
+
+	// store the result as an int64
+	resp.Error = resp.Result.Set(ctx, &result)
+	if resp.Error != nil {
+		return
+	}
+
+	tflog.Debug(ctx, "truncate: successful return", map[string]any{"success": true})
+}