diff --git a/go.mod b/go.mod
index 970c228..d82bcd4 100644
--- a/go.mod
+++ b/go.mod
@@ -2,6 +2,9 @@ module worklog
 
 go 1.22.5
 
-require github.com/alexflint/go-arg v1.5.1
+require (
+	github.com/alexflint/go-arg v1.5.1
+	github.com/atotto/clipboard v0.1.4
+)
 
 require github.com/alexflint/go-scalar v1.2.0 // indirect
diff --git a/go.sum b/go.sum
index 43a8011..276be7c 100644
--- a/go.sum
+++ b/go.sum
@@ -2,6 +2,8 @@ github.com/alexflint/go-arg v1.5.1 h1:nBuWUCpuRy0snAG+uIJ6N0UvYxpxA0/ghA/AaHxlT8
 github.com/alexflint/go-arg v1.5.1/go.mod h1:A7vTJzvjoaSTypg4biM5uYNTkJ27SkNTArtYXnlqVO8=
 github.com/alexflint/go-scalar v1.2.0 h1:WR7JPKkeNpnYIOfHRa7ivM21aWAdHD0gEWHCx+WQBRw=
 github.com/alexflint/go-scalar v1.2.0/go.mod h1:LoFvNMqS1CPrMVltza4LvnGKhaSpc3oyLEBUZVhhS2o=
+github.com/atotto/clipboard v0.1.4 h1:EH0zSVneZPSuFR11BlR9YppQTVDbh5+16AmcJi4g1z4=
+github.com/atotto/clipboard v0.1.4/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
 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/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
diff --git a/main.go b/main.go
index 4d0b2b0..15c1188 100644
--- a/main.go
+++ b/main.go
@@ -5,12 +5,16 @@
 
 package main
 
-import "errors"
-import "os"
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
 
-import "github.com/alexflint/go-arg"
+	"github.com/alexflint/go-arg"
 
-import "worklog/src"
+	"worklog/src"
+)
 
 type Args struct {
 	Decl string   `arg:"-d,--decl" help:"Generate travel declaration table" placeholder:"MONTH"`
@@ -19,27 +23,44 @@ type Args struct {
 }
 
 func (Args) Description() string {
-	return "\nworklog - process a worklog file\n"
+	return "worklog - process a worklog file\n"
 }
 
 func main() {
 	var args Args
 	parser := arg.MustParse(&args)
 
+	// File validation
 	_, err := os.Stat(args.File);
 	if errors.Is(err, os.ErrNotExist) || errors.Is(err, os.ErrPermission) {
 		parser.Fail("file was not readable: " + args.File)
 	}
 
+	// Month validation
+	var month int
+	if args.Decl != "" {
+		month, err = strconv.Atoi(args.Decl)
+		if err != nil || month < 1 || month > 12 {
+			parser.Fail("decl is not a valid month")
+		}
+	}
+
+	// Execute
+
 	if args.Process {
-		var api src.Api = src.MakeApi()
+		var process src.Process = src.MakeProcess()
 		var job = func(line string, line_number int) string {
-			return api.Process(line, line_number)
+			return process.Process(line, line_number)
 		}
-		src.Parse(args.File, job)
+		src.File.Parse(args.File, job, true)
 	}
 
-	if args.Decl != "" {
-		// TODO: generate declaration table..
+	if month > 0 {
+		var decl src.Declaration = src.MakeDeclaration(month)
+		var job = func(line string, line_number int) string {
+			return decl.Generate(line, line_number)
+		}
+		src.File.Parse(args.File, job, false)
+		fmt.Println(decl.Result())
 	}
 }
diff --git a/src/declaration.go b/src/declaration.go
new file mode 100644
index 0000000..b43e0db
--- /dev/null
+++ b/src/declaration.go
@@ -0,0 +1,99 @@
+package src
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/atotto/clipboard"
+)
+
+type Location int
+
+const (
+	NONE Location = iota // 0
+	HOME
+	OFFICE
+	VISIT
+)
+
+type Declaration struct {
+	month int
+	clock_in *regexp.Regexp
+	dates [31]Location
+	result string
+}
+
+// Constructor
+func MakeDeclaration(month int) Declaration {
+	return Declaration{
+		month: month,
+		clock_in: Util.CompileRegex(`^\s*\|\s+[0-9]{4}-[0-9]{2}-[0-9]{2}\s+\|\s+IN\s+\|\s+[0-9]{2}:[0-9]{2}\s+\|\s+[a-zA-Z]+\s+\|`),
+	}
+}
+
+func (self *Declaration) Generate(line string, line_number int) string {
+	var err error
+	if self.clock_in.MatchString(line) {
+		err = self.parseLocation(line, line_number)
+	}
+	assert(err)
+
+	return line
+}
+
+func (self *Declaration) Result() string {
+	var result string
+	for _, date := range self.dates {
+		if date == HOME {
+			result += "x\t\t"
+		} else if date == OFFICE {
+			result +="\tx\t"
+		} else if date == VISIT {
+			result += "\t\tx"
+		}
+		result += "\n"
+	}
+	clipboard.WriteAll(result)
+	result = "-home--office--visit-" + result
+	result = result + "---------------------"
+
+	return result
+}
+
+// -----------------------------------------
+
+func (self *Declaration) parseLocation(line string, line_number int) error {
+	data, err := Util.ParseLine(line, line_number, 4)
+	if err != nil { return err }
+
+	var month_string string = data[0][5:7]
+	month, err := strconv.Atoi(month_string)
+	if err != nil || month < 1 || month > 12 {
+		return fmt.Errorf("invalid month '%s' on line %d\n%s", month_string, line_number, line)
+	}
+
+	var day_string string = data[0][8:]
+	day, err := strconv.Atoi(day_string)
+	if err != nil || day < 1 || day > 31 {
+		return fmt.Errorf("invalid day '%s' on line %d\n%s", day_string, line_number, line)
+	}
+
+	if month == self.month {
+		var data_month = strings.ToLower(data[3])
+		if data_month == strings.ToLower("Home") {
+			self.dates[day - 1] = HOME
+		} else if data_month == strings.ToLower("Office") {
+			self.dates[day - 1] = OFFICE
+		} else if data_month == strings.ToLower("Visit") {
+			self.dates[day - 1] = VISIT
+		} else {
+			return fmt.Errorf("invalid location '%s' on line %d\n%s", data[3], line_number, line)
+		}
+	}
+
+	return nil
+}
+
+// | 2024-07-06 | IN | 08:30 | Office |
diff --git a/src/file.go b/src/file.go
index e4cd194..bd258f1 100644
--- a/src/file.go
+++ b/src/file.go
@@ -3,7 +3,11 @@ package src
 import "bufio"
 import "os"
 
-func Parse(path string, job func(line string, line_number int) string) {
+var File file
+
+type file struct {}
+
+func (file) Parse(path string, job func(line string, line_number int) string, overwrite bool) {
 	// Input file
 	file, err := os.Open(path)
     assert(err)
@@ -11,11 +15,14 @@ func Parse(path string, job func(line string, line_number int) string) {
     var scanner *bufio.Scanner = bufio.NewScanner(file)
 
 	// Output file
-    output_file, err := os.Create(path + ".tmp")
-	assert(err)
-    defer output_file.Close()
-	var writer *bufio.Writer = bufio.NewWriter(output_file)
-    defer writer.Flush()
+	var writer *bufio.Writer
+	if overwrite {
+		output_file, err := os.Create(path + ".tmp")
+		assert(err)
+		defer output_file.Close()
+		writer = bufio.NewWriter(output_file)
+		defer writer.Flush()
+	}
 
 	var line string
 	var line_number int = 1
@@ -25,8 +32,10 @@ func Parse(path string, job func(line string, line_number int) string) {
 		line_number++
 
 		// Write line to output_file
-		_, err := writer.WriteString(line + "\n")
-		assert(err)
+		if writer != nil {
+			_, err := writer.WriteString(line + "\n")
+			assert(err)
+		}
     }
 
 	// Detect table if it was at the end of the file
@@ -35,7 +44,7 @@ func Parse(path string, job func(line string, line_number int) string) {
 	err = scanner.Err()
 	assert(err)
 
-	// move file
+	// TODO: move file
 }
 
 // - [v] while looping, start writing a new file, .tmp, Q: write per line or per chunk? how big are the chunks?
diff --git a/src/api.go b/src/process.go
similarity index 62%
rename from src/api.go
rename to src/process.go
index c5b631f..eaf9bf7 100644
--- a/src/api.go
+++ b/src/process.go
@@ -1,12 +1,8 @@
 package src
 
-import (
-	"errors"
-	"fmt"
-	"regexp"
-	"strconv"
-	"strings"
-)
+import "errors"
+import "fmt"
+import "regexp"
 
 type Date struct {
 	clock_in string
@@ -18,7 +14,7 @@ type Date struct {
 	last_description string
 }
 
-type Api struct {
+type Process struct {
 	clock_in *regexp.Regexp
 	task_line *regexp.Regexp
 	clock_out *regexp.Regexp
@@ -26,16 +22,16 @@ type Api struct {
 }
 
 // Constructor
-func MakeApi() Api {
-	return Api{
-		clock_in: compileRegex(`^\s*\| [0-9]{4}-[0-9]{2}-[0-9]{2} \|\s+IN\s+\|`),
-		task_line: compileRegex(`^\s*\| [0-9]{4}-[0-9]{2}-[0-9]{2} \| [0-9]{2}:[0-9]{2} \|`),
-		clock_out: compileRegex(`^\s*\| [0-9]{4}-[0-9]{2}-[0-9]{2} \|\s+OUT\s+\|`),
+func MakeProcess() Process {
+	return Process{
+		clock_in: Util.CompileRegex(`^\s*\|\s+[0-9]{4}-[0-9]{2}-[0-9]{2}\s+\|\s+IN\s+\|`),
+		task_line: Util.CompileRegex(`^\s*\|\s+[0-9]{4}-[0-9]{2}-[0-9]{2}\s+\|\s+[0-9]{2}:[0-9]{2}\s+\|`),
+		clock_out: Util.CompileRegex(`^\s*\|\s+[0-9]{4}-[0-9]{2}-[0-9]{2}\s+\|\s+OUT\s+\|`),
 		dates: make(map[string]Date),
 	}
 }
 
-func (self *Api) Process(line string, line_number int) string {
+func (self *Process) Process(line string, line_number int) string {
 	var err error
 	if self.clock_in.MatchString(line) {
 		err = self.parseClockIn(line, line_number)
@@ -52,34 +48,8 @@ func (self *Api) Process(line string, line_number int) string {
 
 // -----------------------------------------
 
-func compileRegex(pattern string) *regexp.Regexp {
-    regex, err := regexp.Compile(pattern)
-	assert(err)
-
-	return regex
-}
-
-func (self *Api) parseLine(line string, line_number int, size int) ([]string, error) {
-	var data []string = strings.Split(line, "|")
-
-	if len(data) != size + 2 {
-		return nil, errors.New("malformed line " + strconv.Itoa(line_number) + "\n" + line)
-	}
-
-	data = data[1:size + 1]
-	for i, value := range data {
-        data[i] = strings.TrimSpace(value)
-
-		if len(data[i]) == 0 {
-			return nil, errors.New("malformed line " + strconv.Itoa(line_number) + "\n" + line)
-		}
-	}
-
-	return data, nil
-}
-
-func (self *Api) parseClockIn(line string, line_number int) error {
-	data, err := self.parseLine(line, line_number, 4)
+func (self *Process) parseClockIn(line string, line_number int) error {
+	data, err := Util.ParseLine(line, line_number, 4)
 	if err != nil { return err }
 
 	// Set clock_in, location
@@ -91,8 +61,8 @@ func (self *Api) parseClockIn(line string, line_number int) error {
 	return nil
 }
 
-func (self *Api) parseTask(line string, line_number int) error {
-	data, err := self.parseLine(line, line_number, 5)
+func (self *Process) parseTask(line string, line_number int) error {
+	data, err := Util.ParseLine(line, line_number, 5)
 	if err != nil { return err }
 
 	var date Date = self.dates[data[0]]
@@ -123,8 +93,8 @@ func (self *Api) parseTask(line string, line_number int) error {
 	return nil
 }
 
-func (self *Api) parseClockOut(line string, line_number int) error {
-	data, err := self.parseLine(line, line_number, 3)
+func (self *Process) parseClockOut(line string, line_number int) error {
+	data, err := Util.ParseLine(line, line_number, 3)
 	if err != nil { return err }
 
 	// Set clock_out
@@ -142,7 +112,7 @@ func (self *Api) parseClockOut(line string, line_number int) error {
 	return nil
 }
 
-func (self *Api) callApi(date string, from_time string, to_time string, item_id string, description string) error {
+func (self *Process) callApi(date string, from_time string, to_time string, item_id string, description string) error {
 	fmt.Println("API |" + date + "|" + from_time + "|" + to_time + "|" + item_id + "|" + description)
 
 	// parse line
diff --git a/src/util.go b/src/util.go
new file mode 100644
index 0000000..a1229db
--- /dev/null
+++ b/src/util.go
@@ -0,0 +1,38 @@
+package src
+
+import (
+	"errors"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var Util util
+
+type util struct {}
+
+func (util) CompileRegex(pattern string) *regexp.Regexp {
+    regex, err := regexp.Compile(pattern)
+	assert(err)
+
+	return regex
+}
+
+func (util) ParseLine(line string, line_number int, size int) ([]string, error) {
+	var data []string = strings.Split(line, "|")
+
+	if len(data) != size + 2 {
+		return nil, errors.New("malformed line " + strconv.Itoa(line_number) + "\n" + line)
+	}
+
+	data = data[1:size + 1]
+	for i, value := range data {
+        data[i] = strings.TrimSpace(value)
+
+		if len(data[i]) == 0 {
+			return nil, errors.New("malformed line " + strconv.Itoa(line_number) + "\n" + line)
+		}
+	}
+
+	return data, nil
+}