feat: implemented initial login command

internal/command/command.go

@@ -0,0 +1,76 @@
+package command
+
+import (
+	"fmt"
+
+	"github.com/StevanFreeborn/gator/internal/state"
+)
+
+type Command struct {
+	Name    string
+	Handler CommandHandler
+}
+
+type CommandHandler func(s *state.State) error
+
+func newCommand(name string, handler CommandHandler) *Command {
+	return &Command{
+		Name:    name,
+		Handler: handler,
+	}
+}
+
+type CommandRegistry struct {
+	commands map[string]*Command
+}
+
+func (c *CommandRegistry) register(cmd *Command) error {
+	c.commands[cmd.Name] = cmd
+	return nil
+}
+
+func NewRegistry() *CommandRegistry {
+	cr := CommandRegistry{
+		commands: map[string]*Command{},
+	}
+
+	commands := []*Command{
+		loginCommand(),
+	}
+
+	for _, cmd := range commands {
+		cr.register(cmd)
+	}
+
+	return &cr
+}
+
+func (c *CommandRegistry) RunCommand(cmdName string, s *state.State) error {
+	cmd, found := c.commands[cmdName]
+
+	if !found {
+		return fmt.Errorf("No '%s' registered", cmdName)
+	}
+
+	return cmd.Handler(s)
+}
+
+func loginCommand() *Command {
+	return newCommand("login", func(s *state.State) error {
+		if len(s.Arguments) == 0 {
+			return fmt.Errorf("Did not receive expected username argument")
+		}
+
+		username := s.Arguments[0]
+
+		err := s.Config.SetUser(username)
+
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("Current user set to '%s'\n", username)
+
+		return nil
+	})
+}

internal/config/config.go

@@ -0,0 +1,92 @@
+package config
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path"
+)
+
+const GATOR_CONFIG_FILE = ".gatorconfig.json"
+
+type Config struct {
+	DbUrl           string `json:"db_url"`
+	CurrentUserName string `json:"current_user_name"`
+}
+
+func Read() (*Config, error) {
+	config := Config{}
+
+	configFilePath, err := getConfigPath()
+
+	if err != nil {
+		return nil, err
+	}
+
+	data, err := os.ReadFile(configFilePath)
+
+	if err != nil {
+		return nil, err
+	}
+
+	err = json.Unmarshal(data, &config)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &config, nil
+}
+
+// TODO: I don't think there should be
+// hidden I/O in this method call
+func (c *Config) SetUser(currentUserName string) error {
+	c.CurrentUserName = currentUserName
+	return writeFile(c)
+}
+
+func (c *Config) String() string {
+	return fmt.Sprintf("Config { DbUrl = %s, CurrentUserName = %s }", c.DbUrl, c.CurrentUserName)
+}
+
+func writeFile(config *Config) error {
+	data, err := json.Marshal(config)
+
+	if err != nil {
+		return err
+	}
+
+	configFilePath, err := getConfigPath()
+
+	if err != nil {
+		return err
+	}
+
+	file, err := os.Create(configFilePath)
+
+	if err != nil {
+		return err
+	}
+
+	defer file.Close()
+
+	_, err = file.Write(data)
+
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func getConfigPath() (string, error) {
+	homeDir, err := os.UserHomeDir()
+
+	if err != nil {
+		return "", err
+	}
+
+	configFilePath := path.Join(homeDir, GATOR_CONFIG_FILE)
+
+	return configFilePath, nil
+}

internal/state/state.go

@@ -0,0 +1,12 @@
+package state
+
+import "github.com/StevanFreeborn/gator/internal/config"
+
+type State struct {
+	Config    *config.Config
+	Arguments []string
+}
+
+func NewState(c *config.Config, args []string) *State {
+	return &State{Config: c, Arguments: args}
+}