Add command line flag to specify config file

main.go

@@ -14,6 +14,11 @@ import (
 	"web/renderer"
 	"web/repository"
 	"web/service"
+	"web/util"
+)
+
+var (
+	configFile = "bloat.conf"
 )
 
 func init() {
@@ -21,7 +26,19 @@ func init() {
 }
 
 func main() {
-	config, err := config.ParseFile("default.conf")
+	opts, _, err := util.Getopts(os.Args, "f:")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, opt := range opts {
+		switch opt.Option {
+		case 'f':
+			configFile = opt.Value
+		}
+	}
+
+	config, err := config.ParseFile(configFile)
 	if err != nil {
 		log.Fatal(err)
 	}

util/getopt.go

@@ -0,0 +1,122 @@
+/*
+Copyright 2019 Drew DeVault <sir@cmpwn.com>
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+this list of conditions and the following disclaimer in the documentation
+and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its contributors
+may be used to endorse or promote products derived from this software without
+specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+package util
+
+import (
+	"fmt"
+	"os"
+)
+
+// In the case of "-o example", Option is 'o' and "example" is Value. For
+// options which do not take an argument, Value is "".
+type Option struct {
+	Option rune
+	Value  string
+}
+
+// This is returned when an unknown option is found in argv, but not in the
+// option spec.
+type UnknownOptionError rune
+
+func (e UnknownOptionError) Error() string {
+	return fmt.Sprintf("%s: unknown option -%c", os.Args[0], rune(e))
+}
+
+// This is returned when an option with a mandatory argument is missing that
+// argument.
+type MissingOptionError rune
+
+func (e MissingOptionError) Error() string {
+	return fmt.Sprintf("%s: expected argument for -%c", os.Args[0], rune(e))
+}
+
+// Getopts implements a POSIX-compatible options interface.
+//
+// Returns a slice of options and the index of the first non-option argument.
+//
+// If an error is returned, you must print it to stderr to be POSIX complaint.
+func Getopts(argv []string, spec string) ([]Option, int, error) {
+	optmap := make(map[rune]bool)
+	runes := []rune(spec)
+	for i, rn := range spec {
+		if rn == ':' {
+			if i == 0 {
+				continue
+			}
+			optmap[runes[i-1]] = true
+		} else {
+			optmap[rn] = false
+		}
+	}
+
+	var (
+		i    int
+		opts []Option
+	)
+	for i = 1; i < len(argv); i++ {
+		arg := argv[i]
+		runes = []rune(arg)
+		if len(arg) == 0 || arg == "-" {
+			break
+		}
+		if arg[0] != '-' {
+			break
+		}
+		if arg == "--" {
+			i++
+			break
+		}
+		for j, opt := range runes[1:] {
+			if optopt, ok := optmap[opt]; !ok {
+				opts = append(opts, Option{'?', ""})
+				return opts, i, UnknownOptionError(opt)
+			} else if optopt {
+				if j+1 < len(runes)-1 {
+					opts = append(opts, Option{opt, string(runes[j+2:])})
+					break
+				} else {
+					if i+1 >= len(argv) {
+						if len(spec) >= 1 && spec[0] == ':' {
+							opts = append(opts, Option{':', string(opt)})
+						} else {
+							return opts, i, MissingOptionError(opt)
+						}
+					} else {
+						opts = append(opts, Option{opt, argv[i+1]})
+						i++
+					}
+				}
+			} else {
+				opts = append(opts, Option{opt, ""})
+			}
+		}
+	}
+	return opts, i, nil
+}