From 879b482b7af625c0bcd5981432dd6a9cf226e145 Mon Sep 17 00:00:00 2001
From: Luther Wen Xu <lutherchanpublic+git@gmail.com>
Date: Sat, 30 May 2020 21:31:50 +0800
Subject: [PATCH] feat: Implement level

---
 commands/level.go | 12 ++++++--
 level/level.go    | 73 +++++++++++++++++++++++++++++++++++++++++++++++
 util/format.go    | 32 +++++++++++++++++++++
 3 files changed, 115 insertions(+), 2 deletions(-)
 create mode 100644 level/level.go

diff --git a/commands/level.go b/commands/level.go
index 895abfe..2004a9a 100644
--- a/commands/level.go
+++ b/commands/level.go
@@ -4,6 +4,7 @@ import (
 	"github.com/bwmarrin/discordgo"
 
 	"gitea.teamortix.com/chanbakjsd/Milen/db"
+	"gitea.teamortix.com/chanbakjsd/Milen/level"
 	"gitea.teamortix.com/chanbakjsd/Milen/util"
 )
 
@@ -24,11 +25,18 @@ func handleLevel(dg *discordgo.Session, m *discordgo.MessageCreate, arguments []
 		util.SendFailEmbed(dg, m.ChannelID, "Error", "Cannot find requested member.")
 		return
 	}
+	rank, level := level.GetLevelFromXP(xp)
 	embed := &discordgo.MessageEmbed{
 		Fields: []*discordgo.MessageEmbedField{
 			&discordgo.MessageEmbedField{
-				Name:  "Active Time",
-				Value: util.FormatPlural(xp, "second", "seconds") + " (or " + util.FormatTime(xp) + ")",
+				Name:   "Level",
+				Value:  rank.String() + " " + util.FormatRomanNumeral(level),
+				Inline: true,
+			},
+			&discordgo.MessageEmbedField{
+				Name:   "Active Time",
+				Value:  util.FormatPlural(xp, "second", "seconds") + " (or " + util.FormatTime(xp) + ")",
+				Inline: true,
 			},
 			&discordgo.MessageEmbedField{
 				Name:  "Internal User ID",
diff --git a/level/level.go b/level/level.go
new file mode 100644
index 0000000..9e64164
--- /dev/null
+++ b/level/level.go
@@ -0,0 +1,73 @@
+package level
+
+type Rank uint8
+
+const (
+	RankRecruit Rank = iota
+	RankMember
+	RankApprentice
+	RankAdept
+	RankExperienced
+	RankVeteran
+	RankProfessional
+	RankElite
+	RankEpic
+	RankElder
+	RankLegend
+	RankInsane
+	RankGodlike
+	RankDemigod
+)
+
+func (r Rank) String() string {
+	switch r {
+	case RankRecruit:
+		return "Recruit"
+	case RankMember:
+		return "Member"
+	case RankApprentice:
+		return "Apprentice"
+	case RankAdept:
+		return "Adept"
+	case RankExperienced:
+		return "Experienced"
+	case RankVeteran:
+		return "Veteran"
+	case RankProfessional:
+		return "Professional"
+	case RankElite:
+		return "Elite"
+	case RankEpic:
+		return "Epic"
+	case RankElder:
+		return "Elder"
+	case RankLegend:
+		return "Legend"
+	case RankInsane:
+		return "Insane"
+	case RankGodlike:
+		return "Godlike"
+	case RankDemigod:
+		return "Demigod"
+	}
+	return "Unknown"
+}
+
+func GetLevelFromXP(xp int64) (Rank, int) {
+	// Level starting from 1
+	level := int(xp/600 + 1)
+	rank := 0
+	// Get highest power of 2 we can go without touching it.
+	// 3 => 1 (2^1=2)
+	// 4 => 1 (2^1=2)
+	// 5 => 2 (2^2=4)
+	for level > (1 << rank) {
+		if rank == int(RankDemigod) {
+			break
+		}
+		rank++
+	}
+	rank--
+	// Return it.
+	return Rank(rank), level - (1 << rank) + 1
+}
diff --git a/util/format.go b/util/format.go
index af0dd2b..023da9a 100644
--- a/util/format.go
+++ b/util/format.go
@@ -44,3 +44,35 @@ func FormatPlural(count int64, singular string, plural string) string {
 	}
 	return strconv.FormatInt(count, 10) + " " + plural
 }
+
+func FormatRomanNumeral(number int) string {
+	if number < 1 || number > 3999 {
+		return strconv.Itoa(number)
+	}
+	conversions := []struct {
+		value int
+		digit string
+	}{
+		{1000, "M"},
+		{900, "CM"},
+		{500, "D"},
+		{400, "CD"},
+		{100, "C"},
+		{90, "XC"},
+		{50, "L"},
+		{40, "XL"},
+		{10, "X"},
+		{9, "IX"},
+		{5, "V"},
+		{4, "IV"},
+		{1, "I"},
+	}
+	roman := ""
+	for _, conversion := range conversions {
+		for number >= conversion.value {
+			roman += conversion.digit
+			number -= conversion.value
+		}
+	}
+	return roman
+}