feat: Add fromdateiso8601 and todateiso8601 (#379)

* feat: Add fromdateiso8601 and todateiso8601

* fix: input type

* fix: typo

* fix: fromdateiso8601

* feat: simplify todateiso8601

* refactor: consistent naming

jackson-jq/src/main/java/net/thisptr/jackson/jq/internal/functions/FromDateIso8601Function.java

@@ -0,0 +1,30 @@
+package net.thisptr.jackson.jq.internal.functions;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import com.google.auto.service.AutoService;
+import net.thisptr.jackson.jq.*;
+import net.thisptr.jackson.jq.exception.JsonQueryException;
+import net.thisptr.jackson.jq.internal.misc.Preconditions;
+import net.thisptr.jackson.jq.internal.misc.JsonNodeUtils;
+import net.thisptr.jackson.jq.path.Path;
+
+import java.time.Instant;
+import java.time.format.DateTimeParseException;
+import java.util.List;
+
+@AutoService(Function.class)
+@BuiltinFunction({ "fromdateiso8601/0" })
+public class FromDateIso8601Function implements Function {
+    @Override
+    public void apply(final Scope scope, final List<Expression> args, final JsonNode in, final Path ipath, final PathOutput output, final Version version) throws JsonQueryException {
+        Preconditions.checkInputType("fromdateiso8601", in, JsonNodeType.STRING);
+        try {
+            String iso8601String = in.asText();
+            long epochSeconds = Instant.parse(iso8601String).getEpochSecond();
+            output.emit(JsonNodeUtils.asNumericNode(epochSeconds), null);
+        } catch (DateTimeParseException e) {
+            throw new JsonQueryException(e);
+        }
+    }
+}

jackson-jq/src/main/java/net/thisptr/jackson/jq/internal/functions/ToDateIso8601Function.java

@@ -0,0 +1,30 @@
+package net.thisptr.jackson.jq.internal.functions;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import com.fasterxml.jackson.databind.node.TextNode;
+import com.google.auto.service.AutoService;
+import net.thisptr.jackson.jq.*;
+import net.thisptr.jackson.jq.exception.JsonQueryException;
+import net.thisptr.jackson.jq.internal.misc.Preconditions;
+import net.thisptr.jackson.jq.path.Path;
+
+import java.time.DateTimeException;
+import java.time.Instant;
+import java.util.List;
+
+@AutoService(Function.class)
+@BuiltinFunction({ "todateiso8601/0" })
+public class ToDateIso8601Function implements Function  {
+    @Override
+    public void apply(final Scope scope, final List<Expression> args, final JsonNode in, final Path ipath, final PathOutput output, final Version version) throws JsonQueryException {
+        Preconditions.checkInputType("todateiso8601", in, JsonNodeType.NUMBER);
+        try {
+            long epochSeconds = in.asLong();
+            String iso8601String = Instant.ofEpochSecond(epochSeconds).toString();
+            output.emit(new TextNode(iso8601String), null);
+        } catch (DateTimeException e) {
+            throw new JsonQueryException(e);
+        }        
+    }
+}

jackson-jq/src/test/resources/tests/functions/fromdateiso8601.yaml

@@ -0,0 +1,4 @@
+- q: 'fromdateiso8601(.)'
+  in: "2023-09-30T00:00:00Z"
+  out:
+  - 1696032000

jackson-jq/src/test/resources/tests/functions/todateiso8601.yaml

@@ -0,0 +1,4 @@
+- q: 'todateiso8601(.)'
+  in: 1696032000
+  out:
+  - "2023-09-30T00:00:00Z"