From 5e215c247df41421f013bbd517867db0a36c1996 Mon Sep 17 00:00:00 2001
From: Alex Roitman <aroitman@housecanary.com>
Date: Fri, 4 Jan 2019 14:57:00 -0800
Subject: [PATCH] Add distance_to function to the tile38 namespace in lua.
 distance_to(lat_a, lon_a, lat_b, lon_b) returns distance in meters between
 points A and B.

---
 internal/server/scripts.go | 11 +++++++++++
 tests/scripts_test.go      |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/internal/server/scripts.go b/internal/server/scripts.go
index 587222c6..c30ad0a4 100644
--- a/internal/server/scripts.go
+++ b/internal/server/scripts.go
@@ -13,6 +13,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/tidwall/geojson/geo"
 	"github.com/tidwall/resp"
 	"github.com/tidwall/tile38/internal/log"
 	"github.com/yuin/gopher-lua"
@@ -142,12 +143,22 @@ func (pl *lStatePool) New() *lua.LState {
 		ls.Push(lua.LString(shaSum))
 		return 1
 	}
+	distanceTo := func(ls *lua.LState) int {
+		dt := geo.DistanceTo(
+			float64(ls.ToNumber(1)),
+			float64(ls.ToNumber(2)),
+			float64(ls.ToNumber(3)),
+			float64(ls.ToNumber(4)))
+		ls.Push(lua.LNumber(dt))
+		return 1
+	}
 	var exports = map[string]lua.LGFunction{
 		"call":         call,
 		"pcall":        pcall,
 		"error_reply":  errorReply,
 		"status_reply": statusReply,
 		"sha1hex":      sha1hex,
+		"distance_to":	distanceTo,
 	}
 	L.SetGlobal("tile38", L.SetFuncs(L.NewTable(), exports))
 
diff --git a/tests/scripts_test.go b/tests/scripts_test.go
index 8a87ade3..e879cedf 100644
--- a/tests/scripts_test.go
+++ b/tests/scripts_test.go
@@ -24,6 +24,8 @@ func scripts_BASIC_test(mc *mockServer) error {
 		{"EVAL", "return KEYS[1] .. ' only'", 1, "key1"}, {"key1 only"},
 		{"EVAL", "return KEYS[1] .. ' and ' .. ARGV[1]", 1, "key1", "arg1"}, {"key1 and arg1"},
 		{"EVAL", "return ARGV[1] .. ' and ' .. ARGV[2]", 0, "arg1", "arg2"}, {"arg1 and arg2"},
+		{"EVAL", "return tile38.sha1hex('asdf')", 0}, {"3da541559918a808c2402bba5012f6c60b27661c"},
+		{"EVAL", "return tile38.distance_to(37.7341129, -122.4408378, 37.733, -122.43)", 0}, {"961"},
 	})
 }