feat: colorize log levels

README.md

@@ -16,7 +16,7 @@ Main features:
 4. All non-json logs are captured.
 5. It understands different field names: `time`, `timestamp`, `msg`, `message`, `err`, `error` etc.
 6. It supports case-insensitive filtering.
-7. It is simple.
+7. Colorized log levels.
 
 It uses [antonmedv/fx](https://github.com/antonmedv/fx) for viewing JSON records and [charmbracelet/bubbletea](https://github.com/charmbracelet/bubbletea) for organizing the terminal UI. The tool is inspired by the project [json-log-viewer](https://github.com/gistia/json-log-viewer) which is unfortunately outdated and deserted.
 

assets/example.log

@@ -35,11 +35,11 @@
 {"time":"1970-01-01T00:00:00.00","level":"INFO","message": "Never mistake activity for achievement.","author": "John Wooden"}
 {"time":"1970-01-01T00:00:00.00","level":"INFO","message": "What worries you masters you.","author": "Haddon Robinson"}
 {"time":"1970-01-01T00:00:00.00","level":"INFO","message": "One faces the future with ones past.","author": "Pearl Buck"}
-{"time":"1970-01-01T00:00:00.00","level":"INFO","message": "Goals are the fuel in the furnace of achievement.","author": "Brian Tracy"}
-{"time":"1970-01-01T00:00:00.00","level":"INFO","message": "Who sows virtue reaps honour.","author": "Leonardo da Vinci"}
+{"time":"1970-01-01T00:00:00.00","level":"VERBOSE","message": "Goals are the fuel in the furnace of achievement.","author": "Brian Tracy"}
 {"time":"1970-01-01T00:00:00.00","level":"FATAL","message": "Be the chief but never the lord.","author": "Lao Tzu"}
 {"time":"1970-01-01T00:00:00.00","level":"PANIC","message": "Fate is in your hands and no one elses","author": "Byron Pulsifer"}
 {"time":"1970-01-01T00:00:00.00","level":"ERROR","message": "Genius is one percent inspiration and ninety-nine percent perspiration.","author": "Thomas Edison"}
+{"time":"1970-01-01T00:00:00.00","level":"WARN","message": "Who sows virtue reaps honour.","author": "Leonardo da Vinci"}
 {"time":"1970-01-01T00:00:00.00","level":"INFO","message": "You can observe a lot just by watching.","author": "Yogi Berra"}
 {"time":"1970-01-01T00:00:00.00","level":"DEBUG","message": "A house divided against itself cannot stand.","author": "Abraham Lincoln"}
 {"time":"1970-01-01T00:00:00.00","level":"TRACE","message": "Difficulties increase the nearer we get to the goal.","author": "Johann Wolfgang von Goethe"}

go.mod

@@ -4,6 +4,8 @@ go 1.20
 
 replace github.com/antonmedv/fx => github.com/hedhyw/fx v0.0.1
 
+replace github.com/charmbracelet/bubbles => github.com/hedhyw/bubbles v0.0.2
+
 require (
 	github.com/antonmedv/fx v0.0.0-20230706101337-4fec4e492a52
 	github.com/charmbracelet/bubbles v0.16.1
@@ -19,20 +21,22 @@ require (
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/containerd/console v1.0.4-0.20230313162750-1ae8d489ac81 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/kr/pretty v0.3.0 // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
-	github.com/mattn/go-isatty v0.0.18 // indirect
+	github.com/mattn/go-isatty v0.0.19 // indirect
 	github.com/mattn/go-localereader v0.0.1 // indirect
 	github.com/mattn/go-runewidth v0.0.14 // indirect
 	github.com/mazznoer/colorgrad v0.9.1 // indirect
 	github.com/mazznoer/csscolorparser v0.1.3 // indirect
 	github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6 // indirect
 	github.com/muesli/cancelreader v0.2.2 // indirect
-	github.com/muesli/termenv v0.15.1 // indirect
+	github.com/muesli/termenv v0.15.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rivo/uniseg v0.4.4 // indirect
-	golang.org/x/sync v0.1.0 // indirect
-	golang.org/x/sys v0.7.0 // indirect
-	golang.org/x/term v0.7.0 // indirect
-	golang.org/x/text v0.9.0 // indirect
+	golang.org/x/sync v0.3.0 // indirect
+	golang.org/x/sys v0.10.0 // indirect
+	golang.org/x/term v0.10.0 // indirect
+	golang.org/x/text v0.11.0 // indirect
+	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -2,22 +2,31 @@ github.com/atotto/clipboard v0.1.4 h1:EH0zSVneZPSuFR11BlR9YppQTVDbh5+16AmcJi4g1z
 github.com/atotto/clipboard v0.1.4/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
-github.com/charmbracelet/bubbles v0.16.1 h1:6uzpAAaT9ZqKssntbvZMlksWHruQLNxg49H5WdeuYSY=
-github.com/charmbracelet/bubbles v0.16.1/go.mod h1:2QCp9LFlEsBQMvIYERr7Ww2H2bA7xen1idUDIzm/+Xc=
 github.com/charmbracelet/bubbletea v0.24.2 h1:uaQIKx9Ai6Gdh5zpTbGiWpytMU+CfsPp06RaW2cx/SY=
 github.com/charmbracelet/bubbletea v0.24.2/go.mod h1:XdrNrV4J8GiyshTtx3DNuYkR1FDaJmO3l2nejekbsgg=
 github.com/charmbracelet/lipgloss v0.7.1 h1:17WMwi7N1b1rVWOjMT+rCh7sQkvDU75B2hbZpc5Kc1E=
 github.com/charmbracelet/lipgloss v0.7.1/go.mod h1:yG0k3giv8Qj8edTCbbg6AlQ5e8KNWpFujkNawKNhE2c=
 github.com/containerd/console v1.0.4-0.20230313162750-1ae8d489ac81 h1:q2hJAaP1k2wIvVRd/hEHD7lacgqrCPS+k8g1MndzfWY=
 github.com/containerd/console v1.0.4-0.20230313162750-1ae8d489ac81/go.mod h1:YynlIjWYF8myEu6sdkwKIvGQq+cOckRm6So2avqoYAk=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/hedhyw/bubbles v0.0.2 h1:OqPNGSunmk2B8wE4RcZ4oQvhWkCZNYt8EY8UXuuXJuw=
+github.com/hedhyw/bubbles v0.0.2/go.mod h1:XUdibuVUiMfcfKTRla58bmY3TWsdjgF+Rp8pvimQLck=
 github.com/hedhyw/fx v0.0.1 h1:h1jJaDnJ6qewSKiD7yooAGZjQwS+yazFcoRgtWV0Rq8=
 github.com/hedhyw/fx v0.0.1/go.mod h1:mT/W/Ln5xzLNEh+wGWAsPITPpQV5w6ne7klykEUS78w=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
+github.com/kr/pretty v0.3.0 h1:WgNl7dwNpEZ6jJ9k1snq4pZsg7DOEN8hP9Xw0Tsjwk0=
+github.com/kr/pretty v0.3.0/go.mod h1:640gp4NfQd8pI5XOwp5fnNeVWj67G7CFk/SaSQn7NBk=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
 github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
-github.com/mattn/go-isatty v0.0.18 h1:DOKFKCQ7FNG2L1rbrmstDN4QVRdS89Nkh85u68Uwp98=
-github.com/mattn/go-isatty v0.0.18/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/mattn/go-isatty v0.0.19 h1:JITubQf0MOLdlGRuRq+jtsDlekdYPia9ZFsB8h/APPA=
+github.com/mattn/go-isatty v0.0.19/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/mattn/go-localereader v0.0.1 h1:ygSAOl7ZXTx4RdPYinUpg6W99U8jWvWi9Ye2JC/oIi4=
 github.com/mattn/go-localereader v0.0.1/go.mod h1:8fBrzywKY7BI3czFoHkuzRoWE9C+EiG4R1k4Cjx5p88=
 github.com/mattn/go-runewidth v0.0.12/go.mod h1:RAqKPSqVFrSLVXbA8x7dzmKdmGzieGRCM46jaSJTDAk=
@@ -34,29 +43,34 @@ github.com/muesli/cancelreader v0.2.2 h1:3I4Kt4BQjOR54NavqnDogx/MIoWBFa0StPA8ELU
 github.com/muesli/cancelreader v0.2.2/go.mod h1:3XuTXfFS2VjM+HTLZY9Ak0l6eUKfijIfMUZ4EgX0QYo=
 github.com/muesli/reflow v0.3.0 h1:IFsN6K9NfGtjeggFP+68I4chLZV2yIKsXJFNZ+eWh6s=
 github.com/muesli/reflow v0.3.0/go.mod h1:pbwTDkVPibjO2kyvBQRBxTWEEGDGq0FlB1BIKtnHY/8=
-github.com/muesli/termenv v0.15.1 h1:UzuTb/+hhlBugQz28rpzey4ZuKcZ03MeKsoG7IJZIxs=
-github.com/muesli/termenv v0.15.1/go.mod h1:HeAQPTzpfs016yGtA4g00CsdYnVLJvxsS4ANqrZs2sQ=
+github.com/muesli/termenv v0.15.2 h1:GohcuySI0QmI3wN8Ok9PtKGkgkFIk7y6Vpb5PvrY+Wo=
+github.com/muesli/termenv v0.15.2/go.mod h1:Epx+iuz8sNs7mNKhxzH4fWXGNpZwUaJKRS1noLXviQ8=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.4.4 h1:8TfxU8dW6PdqD27gjM8MVNuicgxIjxpm4K7x4jp8sis=
 github.com/rivo/uniseg v0.4.4/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/rogpeppe/go-internal v1.6.1 h1:/FiVV8dS/e+YqF2JvO3yXRFbBLTIuSDkuC7aBOAvL+k=
+github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/valyala/fastjson v1.6.4 h1:uAUNq9Z6ymTgGhcm0UynUAB6tlbakBrz6CQFax3BXVQ=
 github.com/valyala/fastjson v1.6.4/go.mod h1:CLCAqky6SMuOcxStkYQvblddUtoRxhYMGLrsQns1aXY=
-golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.3.0 h1:ftCYgMx6zT/asHUrPw8BLLscYtGznsLAnjq5RH9P66E=
+golang.org/x/sync v0.3.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
 golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.7.0 h1:3jlCCIQZPdOYu1h8BkNvLz8Kgwtae2cagcG/VamtZRU=
-golang.org/x/sys v0.7.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.7.0 h1:BEvjmm5fURWqcfbSKTdpkDXYBrUS1c0m8agp14W48vQ=
-golang.org/x/term v0.7.0/go.mod h1:P32HKFT3hSsZrRxla30E9HqToFYAQPCMs/zFMBUFqPY=
-golang.org/x/text v0.9.0 h1:2sjJmO8cDvYveuX97RDLsxlyUxLl+GHoLxBiRdHllBE=
-golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+golang.org/x/sys v0.10.0 h1:SqMFp9UcQJZa+pmYuAKjd9xq1f0j5rLcDIk0mj4qAsA=
+golang.org/x/sys v0.10.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.10.0 h1:3R7pNqamzBraeqj/Tj8qt1aQ2HpmlC+Cx/qL/7hn4/c=
+golang.org/x/term v0.10.0/go.mod h1:lpqdcUyK/oCiQxvxVrppt5ggO2KCZ5QblwqPnfZ6d5o=
+golang.org/x/text v0.11.0 h1:LAntKIrcmeSKERyiOh0XMV39LXS8IE9UL2yP7+f5ij4=
+golang.org/x/text v0.11.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
+gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/app/handler.go

@@ -6,6 +6,8 @@ import (
 	"github.com/hedhyw/json-log-viewer/internal/pkg/source"
 )
 
+const cellIDLogLevel = 1
+
 func (m Model) handleKeyMsg(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 	switch msg.String() {
 	case "esc":
@@ -44,12 +46,26 @@ func (m Model) handleWindowSizeMsg(msg tea.WindowSizeMsg) Model {
 }
 
 func (m Model) handleLogEntriesMsg(msg source.LogEntries) Model {
-	m.table.SetRows(msg.Rows())
-
 	if len(m.allLogEntries) == 0 {
 		m.allLogEntries = msg
+
+		tableStyles := getTableStyles()
+		tableStyles.RenderCell = func(value string, rowID, columnID int) string {
+			style := tableStyles.Cell
+
+			if columnID == cellIDLogLevel {
+				return removeClearSequence(
+					m.getLogLevelStyle(style, rowID).Render(value),
+				)
+			}
+
+			return style.Render(value)
+		}
+
+		m.table.SetStyles(tableStyles)
 	}
 
+	m.table.SetRows(msg.Rows())
 	m.filteredLogEntries = msg
 
 	return m

internal/app/helper.go

@@ -1,6 +1,10 @@
 package app
 
-import "github.com/charmbracelet/bubbles/table"
+import (
+	"strings"
+
+	"github.com/charmbracelet/bubbles/table"
+)
 
 func getColumns(width int) []table.Column {
 	const (
@@ -14,3 +18,8 @@ func getColumns(width int) []table.Column {
 		{Title: "Message", Width: width - widthTime - widthLevel},
 	}
 }
+
+func removeClearSequence(value string) string {
+	// https://github.com/charmbracelet/lipgloss/issues/144
+	return strings.ReplaceAll(value, "\x1b[0", "\x1b[39")
+}

internal/app/style.go

@@ -3,6 +3,17 @@ package app
 import (
 	"github.com/charmbracelet/bubbles/table"
 	"github.com/charmbracelet/lipgloss"
+
+	"github.com/hedhyw/json-log-viewer/internal/pkg/source"
+)
+
+// Possible colors.
+const (
+	colorMagenta lipgloss.Color = "13"
+	colorYellow  lipgloss.Color = "11"
+	colorGreen   lipgloss.Color = "10"
+	colorOrange  lipgloss.Color = "214"
+	colorRed     lipgloss.Color = "9"
 )
 
 func getTableStyles() table.Styles {
@@ -29,3 +40,35 @@ func getBaseStyle() lipgloss.Style {
 func getFooterStyle() lipgloss.Style {
 	return lipgloss.NewStyle().Height(footerSize).PaddingLeft(2)
 }
+
+func (m Model) getLogLevelStyle(baseStyle lipgloss.Style, rowID int) lipgloss.Style {
+	if rowID < 0 || rowID >= len(m.filteredLogEntries) {
+		return baseStyle
+	}
+
+	color := getColorForLogLevel(m.filteredLogEntries[rowID].Level)
+	if color == "" {
+		return baseStyle
+	}
+
+	return baseStyle.Copy().Foreground(color)
+}
+
+func getColorForLogLevel(level source.Level) lipgloss.Color {
+	switch level {
+	case source.LevelTrace:
+		return colorMagenta
+	case source.LevelDebug:
+		return colorYellow
+	case source.LevelInfo:
+		return colorGreen
+	case source.LevelWarning:
+		return colorOrange
+	case source.LevelError,
+		source.LevelFatal,
+		source.LevelPanic:
+		return colorRed
+	default:
+		return ""
+	}
+}

internal/app/style_test.go

@@ -0,0 +1,60 @@
+package app
+
+import (
+	"testing"
+
+	"github.com/charmbracelet/lipgloss"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/hedhyw/json-log-viewer/internal/pkg/source"
+)
+
+func TestGetColorForLogLevel(t *testing.T) {
+	t.Parallel()
+
+	testCases := [...]struct {
+		Level    source.Level
+		Expected lipgloss.Color
+	}{{
+		Level:    source.Level(""),
+		Expected: "",
+	}, {
+		Level:    source.LevelUnknown,
+		Expected: "",
+	}, {
+		Level:    source.Level("custom"),
+		Expected: "",
+	}, {
+		Level:    source.LevelTrace,
+		Expected: colorMagenta,
+	}, {
+		Level:    source.LevelDebug,
+		Expected: colorYellow,
+	}, {
+		Level:    source.LevelInfo,
+		Expected: colorGreen,
+	}, {
+		Level:    source.LevelWarning,
+		Expected: colorOrange,
+	}, {
+		Level:    source.LevelError,
+		Expected: colorRed,
+	}, {
+		Level:    source.LevelFatal,
+		Expected: colorRed,
+	}, {
+		Level:    source.LevelPanic,
+		Expected: colorRed,
+	}}
+
+	for _, testCase := range testCases {
+		testCase := testCase
+
+		t.Run(testCase.Level.String(), func(t *testing.T) {
+			t.Parallel()
+
+			actual := getColorForLogLevel(testCase.Level)
+			assert.Equal(t, testCase.Expected, actual)
+		})
+	}
+}

internal/pkg/source/helper.go

@@ -18,11 +18,8 @@ func extractTime(value *fastjson.Value) string {
 
 func extractLevel(value *fastjson.Value) Level {
 	level := extractValue(value, "level", "lvl")
-	if level != "" {
-		return Level(strings.TrimSpace(strings.ToLower(level)))
-	}
 
-	return LevelUnknown
+	return ParseLevel(level)
 }
 
 func extractValue(value *fastjson.Value, keys ...string) string {

internal/pkg/source/level.go

@@ -5,6 +5,34 @@ import "strings"
 // Level of the logs entity.
 type Level string
 
+// ParseLevel parses level from the text value.
+func ParseLevel(value string) Level {
+	value = strings.ToLower(value)
+	value = strings.TrimSpace(value)
+
+	switch {
+	case value == "":
+		return LevelUnknown
+	case strings.HasPrefix(value, "t"),
+		strings.HasPrefix(value, "v"): // Verbose.
+		return LevelTrace
+	case strings.HasPrefix(value, "d"):
+		return LevelDebug
+	case strings.HasPrefix(value, "e"):
+		return LevelError
+	case strings.HasPrefix(value, "i"):
+		return LevelInfo
+	case strings.HasPrefix(value, "w"):
+		return LevelWarning
+	case strings.HasPrefix(value, "f"):
+		return LevelFatal
+	case strings.HasPrefix(value, "p"):
+		return LevelPanic
+	default:
+		return Level(value)
+	}
+}
+
 // String implement fmt.Stringer interface.
 func (l Level) String() string {
 	return strings.ToLower(string(l))
@@ -13,4 +41,11 @@ func (l Level) String() string {
 // Possible log levels.
 const (
 	LevelUnknown Level = "none"
+	LevelTrace   Level = "trace"
+	LevelDebug   Level = "debug"
+	LevelInfo    Level = "info"
+	LevelWarning Level = "warn"
+	LevelError   Level = "error"
+	LevelPanic   Level = "panic"
+	LevelFatal   Level = "fatal"
 )