From 75920481b1128a9715975d4ab0c631eeab37d6c4 Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Thu, 2 Feb 2023 12:42:36 +1100
Subject: [PATCH] Added from_unix operator #1535

---
 pkg/yqlib/doc/operators/datetime.md | 12 +++++++++
 pkg/yqlib/lexer_participle.go       |  1 +
 pkg/yqlib/lib.go                    |  1 +
 pkg/yqlib/operator_datetime.go      | 41 +++++++++++++++++++++++++++++
 pkg/yqlib/operator_datetime_test.go |  8 ++++++
 5 files changed, 63 insertions(+)

diff --git a/pkg/yqlib/doc/operators/datetime.md b/pkg/yqlib/doc/operators/datetime.md
index 0dc3ed5e..3a2fb72d 100644
--- a/pkg/yqlib/doc/operators/datetime.md
+++ b/pkg/yqlib/doc/operators/datetime.md
@@ -86,6 +86,18 @@ a: cool
 updated: 2021-05-19T01:02:03Z
 ```
 
+## From Unix
+Converts from unix time
+
+Running
+```bash
+yq --null-input '1675301929 | from_unix'
+```
+will output
+```yaml
+2023-02-02T12:38:49+11:00
+```
+
 ## Timezone: from standard RFC3339 format
 Returns a new datetime in the specified timezone. Specify standard IANA Time Zone format or 'utc', 'local'. When given a single parameter, this assumes the datetime is in RFC3339 format.
 
diff --git a/pkg/yqlib/lexer_participle.go b/pkg/yqlib/lexer_participle.go
index 09e9dd75..cedbd110 100644
--- a/pkg/yqlib/lexer_participle.go
+++ b/pkg/yqlib/lexer_participle.go
@@ -45,6 +45,7 @@ var participleYqRules = []*participleYqRule{
 	simpleOp("format_datetime", formatDateTimeOpType),
 	simpleOp("now", nowOpType),
 	simpleOp("tz", tzOpType),
+	simpleOp("from_?unix", fromUnixOpType),
 	simpleOp("with_dtf", withDtFormatOpType),
 	simpleOp("error", errorOpType),
 	simpleOp("sortKeys", sortKeysOpType),
diff --git a/pkg/yqlib/lib.go b/pkg/yqlib/lib.go
index 1bb7f405..12b299fd 100644
--- a/pkg/yqlib/lib.go
+++ b/pkg/yqlib/lib.go
@@ -93,6 +93,7 @@ var formatDateTimeOpType = &operationType{Type: "FORMAT_DATE_TIME", NumArgs: 1,
 var withDtFormatOpType = &operationType{Type: "WITH_DATE_TIME_FORMAT", NumArgs: 1, Precedence: 50, Handler: withDateTimeFormat}
 var nowOpType = &operationType{Type: "NOW", NumArgs: 0, Precedence: 50, Handler: nowOp}
 var tzOpType = &operationType{Type: "TIMEZONE", NumArgs: 1, Precedence: 50, Handler: tzOp}
+var fromUnixOpType = &operationType{Type: "FROM_UNIX", NumArgs: 0, Precedence: 50, Handler: fromUnixOp}
 
 var encodeOpType = &operationType{Type: "ENCODE", NumArgs: 0, Precedence: 50, Handler: encodeOperator}
 var decodeOpType = &operationType{Type: "DECODE", NumArgs: 0, Precedence: 50, Handler: decodeOperator}
diff --git a/pkg/yqlib/operator_datetime.go b/pkg/yqlib/operator_datetime.go
index c3ec05f6..f639c540 100644
--- a/pkg/yqlib/operator_datetime.go
+++ b/pkg/yqlib/operator_datetime.go
@@ -4,6 +4,7 @@ import (
 	"container/list"
 	"errors"
 	"fmt"
+	"strconv"
 	"time"
 
 	"gopkg.in/yaml.v3"
@@ -129,3 +130,43 @@ func tzOp(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode)
 
 	return context.ChildContext(results), nil
 }
+
+func parseUnixTime(unixTime string) (time.Time, error) {
+	seconds, err := strconv.ParseFloat(unixTime, 64)
+
+	if err != nil {
+		return time.Now(), err
+	}
+
+	return time.UnixMilli(int64(seconds * 1000)), nil
+}
+
+func fromUnixOp(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+
+	var results = list.New()
+
+	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+
+		actualTag := guessTagFromCustomType(candidate.Node)
+
+		if actualTag != "!!int" && guessTagFromCustomType(candidate.Node) != "!!float" {
+			return Context{}, fmt.Errorf("from_unix only works on numbers, found %v instead", candidate.Node.Tag)
+		}
+
+		parsedTime, err := parseUnixTime(candidate.Node.Value)
+		if err != nil {
+			return Context{}, err
+		}
+
+		node := &yaml.Node{
+			Kind:  yaml.ScalarNode,
+			Tag:   "!!timestamp",
+			Value: parsedTime.Format(time.RFC3339),
+		}
+
+		results.PushBack(candidate.CreateReplacement(node))
+	}
+
+	return context.ChildContext(results), nil
+}
diff --git a/pkg/yqlib/operator_datetime_test.go b/pkg/yqlib/operator_datetime_test.go
index a1d2692f..74b81390 100644
--- a/pkg/yqlib/operator_datetime_test.go
+++ b/pkg/yqlib/operator_datetime_test.go
@@ -39,6 +39,14 @@ var dateTimeOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::a: cool\nupdated: 2021-05-19T01:02:03Z\n",
 		},
 	},
+	{
+		description:    "From Unix",
+		subdescription: "Converts from unix time",
+		expression:     `1675301929 | from_unix`,
+		expected: []string{
+			"D0, P[], (!!timestamp)::2023-02-02T12:38:49+11:00\n",
+		},
+	},
 	{
 		description:    "Timezone: from standard RFC3339 format",
 		subdescription: "Returns a new datetime in the specified timezone. Specify standard IANA Time Zone format or 'utc', 'local'. When given a single parameter, this assumes the datetime is in RFC3339 format.",