Rewrite README.md sentence by sentence (closes #190)

README.md is rewritten from scratch against the rules on issue 190 and
checked statement by statement against the code on next. It leads with
what the program is and how to use it, puts every endpoint, command,
numeric reply, mode and setting in reference sections, and ends with
development and testing. Where the old text disagreed with the code,
the code decides; the PR body lists each case. The hashcash examples
are real 20-bit stamps. REPO_POLICIES.md and CONVENTIONS.md are copies
of shared documents and are untouched.

Model: fable-5-1

internal/config/config.go

@@ -3,11 +3,8 @@ package config
 
 import (
 	"errors"
-	"fmt"
 	"log/slog"
 	"os"
-	"strconv"
-	"time"
 
 	"github.com/spf13/viper"
 	"go.uber.org/fx"
@@ -66,8 +63,6 @@ type Config struct {
 }
 
 // New creates a new Config by reading from files and environment variables.
-// It returns an error when a number, true/false or duration setting does
-// not parse.
 func New(
 	_ fx.Lifecycle, params Params,
 ) (*Config, error) {
@@ -112,27 +107,29 @@ func New(
 
 	cfg := &Config{
 		DBURL:              viper.GetString("DBURL"),
+		Debug:              viper.GetBool("DEBUG"),
+		Port:               viper.GetInt("PORT"),
 		SentryDSN:          viper.GetString("SENTRY_DSN"),
+		MaintenanceMode:    viper.GetBool("MAINTENANCE_MODE"),
 		MetricsUsername:    viper.GetString("METRICS_USERNAME"),
 		MetricsPassword:    viper.GetString("METRICS_PASSWORD"),
 		MessageMaxAge:      viper.GetString("MESSAGE_MAX_AGE"),
+		MaxMessageSize:     viper.GetInt("MAX_MESSAGE_SIZE"),
 		QueueMaxAge:        viper.GetString("QUEUE_MAX_AGE"),
 		MOTD:               viper.GetString("MOTD"),
 		ServerName:         viper.GetString("SERVER_NAME"),
 		FederationKey:      viper.GetString("FEDERATION_KEY"),
 		SessionIdleTimeout: viper.GetString("SESSION_IDLE_TIMEOUT"),
+		HashcashBits:       viper.GetInt("NEOIRC_HASHCASH_BITS"),
 		OperName:           viper.GetString("NEOIRC_OPER_NAME"),
 		OperPassword:       viper.GetString("NEOIRC_OPER_PASSWORD"),
+		LoginRateLimit:     viper.GetFloat64("LOGIN_RATE_LIMIT"),
+		LoginRateBurst:     viper.GetInt("LOGIN_RATE_BURST"),
 		IRCListenAddr:      viper.GetString("IRC_LISTEN_ADDR"),
 		log:                log,
 		params:             &params,
 	}
 
-	err = parseSettings(cfg)
-	if err != nil {
-		return nil, err
-	}
-
 	// Viper counts an empty environment variable as unset, but an
 	// empty IRC_LISTEN_ADDR must turn the IRC listener off.
 	ircListenAddr, set := os.LookupEnv("IRC_LISTEN_ADDR")
@@ -147,68 +144,3 @@ func New(
 
 	return cfg, nil
 }
-
-// parseSettings reads the number and true/false settings into cfg and
-// checks that each duration setting is a valid Go duration. Its error
-// names each setting whose value does not parse.
-func parseSettings(cfg *Config) error {
-	return errors.Join(
-		parseInt("PORT", &cfg.Port),
-		parseInt("MAX_MESSAGE_SIZE", &cfg.MaxMessageSize),
-		parseInt("NEOIRC_HASHCASH_BITS", &cfg.HashcashBits),
-		parseInt("LOGIN_RATE_BURST", &cfg.LoginRateBurst),
-		parseFloat("LOGIN_RATE_LIMIT", &cfg.LoginRateLimit),
-		parseBool("DEBUG", &cfg.Debug),
-		parseBool("MAINTENANCE_MODE", &cfg.MaintenanceMode),
-		checkDuration("MESSAGE_MAX_AGE", cfg.MessageMaxAge),
-		checkDuration("QUEUE_MAX_AGE", cfg.QueueMaxAge),
-		checkDuration("SESSION_IDLE_TIMEOUT", cfg.SessionIdleTimeout),
-	)
-}
-
-// parseInt sets *value to the setting key read as a whole number.
-func parseInt(key string, value *int) error {
-	parsed, err := strconv.Atoi(viper.GetString(key))
-	if err != nil {
-		return fmt.Errorf("cannot parse %s: %w", key, err)
-	}
-
-	*value = parsed
-
-	return nil
-}
-
-// parseFloat sets *value to the setting key read as a decimal number.
-func parseFloat(key string, value *float64) error {
-	parsed, err := strconv.ParseFloat(viper.GetString(key), 64)
-	if err != nil {
-		return fmt.Errorf("cannot parse %s: %w", key, err)
-	}
-
-	*value = parsed
-
-	return nil
-}
-
-// parseBool sets *value to the setting key read as true or false.
-func parseBool(key string, value *bool) error {
-	parsed, err := strconv.ParseBool(viper.GetString(key))
-	if err != nil {
-		return fmt.Errorf("cannot parse %s: %w", key, err)
-	}
-
-	*value = parsed
-
-	return nil
-}
-
-// checkDuration returns an error naming the setting key when value is
-// not a valid Go duration.
-func checkDuration(key, value string) error {
-	_, err := time.ParseDuration(value)
-	if err != nil {
-		return fmt.Errorf("cannot parse %s: %w", key, err)
-	}
-
-	return nil
-}

internal/config/config_test.go

@@ -2,7 +2,6 @@ package config_test
 
 import (
 	"os"
-	"strings"
 	"testing"
 	"time"
 
@@ -11,8 +10,7 @@ import (
 	"sneak.berlin/go/neoirc/internal/logger"
 )
 
-// loadConfig runs config.New and returns its result.
-func loadConfig(t *testing.T) (*config.Config, error) {
+func newConfig(t *testing.T) *config.Config {
 	t.Helper()
 
 	globs := &globals.Globals{
@@ -26,15 +24,9 @@ func loadConfig(t *testing.T) (*config.Config, error) {
 		t.Fatal(err)
 	}
 
-	return config.New(
+	cfg, err := config.New(
 		nil, config.Params{Globals: globs, Logger: log},
 	)
-}
-
-func newConfig(t *testing.T) *config.Config {
-	t.Helper()
-
-	cfg, err := loadConfig(t)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -42,137 +34,6 @@ func newConfig(t *testing.T) *config.Config {
 	return cfg
 }
 
-func TestUnsetSettingsKeepDefaults(t *testing.T) {
-	// Viper counts an empty environment variable as unset.
-	t.Setenv("PORT", "")
-	t.Setenv("MAX_MESSAGE_SIZE", "")
-	t.Setenv("NEOIRC_HASHCASH_BITS", "")
-	t.Setenv("LOGIN_RATE_BURST", "")
-	t.Setenv("LOGIN_RATE_LIMIT", "")
-	t.Setenv("DEBUG", "")
-	t.Setenv("MAINTENANCE_MODE", "")
-	t.Setenv("MESSAGE_MAX_AGE", "")
-	t.Setenv("QUEUE_MAX_AGE", "")
-	t.Setenv("SESSION_IDLE_TIMEOUT", "")
-
-	// Each duration setting defaults to 30 days.
-	const thirtyDays = "720h"
-
-	want := settings{
-		Port:               8080,
-		MaxMessageSize:     4096,
-		HashcashBits:       20,
-		LoginRateBurst:     5,
-		LoginRateLimit:     1,
-		Debug:              false,
-		MaintenanceMode:    false,
-		MessageMaxAge:      thirtyDays,
-		QueueMaxAge:        thirtyDays,
-		SessionIdleTimeout: thirtyDays,
-	}
-
-	got := settingsOf(newConfig(t))
-	if got != want {
-		t.Errorf("settings = %+v, want %+v", got, want)
-	}
-}
-
-func TestValidSettingsAreUsed(t *testing.T) {
-	t.Setenv("PORT", "9000")
-	t.Setenv("MAX_MESSAGE_SIZE", "1024")
-	t.Setenv("NEOIRC_HASHCASH_BITS", "0")
-	t.Setenv("LOGIN_RATE_BURST", "10")
-	t.Setenv("LOGIN_RATE_LIMIT", "0.5")
-	t.Setenv("DEBUG", "true")
-	t.Setenv("MAINTENANCE_MODE", "true")
-	t.Setenv("MESSAGE_MAX_AGE", "24h")
-	t.Setenv("QUEUE_MAX_AGE", "1h30m")
-	t.Setenv("SESSION_IDLE_TIMEOUT", "0")
-
-	want := settings{
-		Port:               9000,
-		MaxMessageSize:     1024,
-		HashcashBits:       0,
-		LoginRateBurst:     10,
-		LoginRateLimit:     0.5,
-		Debug:              true,
-		MaintenanceMode:    true,
-		MessageMaxAge:      "24h",
-		QueueMaxAge:        "1h30m",
-		SessionIdleTimeout: "0",
-	}
-
-	got := settingsOf(newConfig(t))
-	if got != want {
-		t.Errorf("settings = %+v, want %+v", got, want)
-	}
-}
-
-// settings holds the Config fields whose settings config.New parses.
-type settings struct {
-	Port               int
-	MaxMessageSize     int
-	HashcashBits       int
-	LoginRateBurst     int
-	LoginRateLimit     float64
-	Debug              bool
-	MaintenanceMode    bool
-	MessageMaxAge      string
-	QueueMaxAge        string
-	SessionIdleTimeout string
-}
-
-func settingsOf(cfg *config.Config) settings {
-	return settings{
-		Port:               cfg.Port,
-		MaxMessageSize:     cfg.MaxMessageSize,
-		HashcashBits:       cfg.HashcashBits,
-		LoginRateBurst:     cfg.LoginRateBurst,
-		LoginRateLimit:     cfg.LoginRateLimit,
-		Debug:              cfg.Debug,
-		MaintenanceMode:    cfg.MaintenanceMode,
-		MessageMaxAge:      cfg.MessageMaxAge,
-		QueueMaxAge:        cfg.QueueMaxAge,
-		SessionIdleTimeout: cfg.SessionIdleTimeout,
-	}
-}
-
-func TestUnparseableSettingStopsStartup(t *testing.T) {
-	tests := []struct {
-		key   string
-		value string
-	}{
-		{key: "PORT", value: "80a"},
-		{key: "MAX_MESSAGE_SIZE", value: "4k"},
-		{key: "NEOIRC_HASHCASH_BITS", value: "twenty"},
-		{key: "LOGIN_RATE_BURST", value: "five"},
-		{key: "LOGIN_RATE_LIMIT", value: "fast"},
-		{key: "DEBUG", value: "yes"},
-		{key: "MAINTENANCE_MODE", value: "on"},
-		{key: "MESSAGE_MAX_AGE", value: "30d"},
-		{key: "QUEUE_MAX_AGE", value: "720"},
-		{key: "SESSION_IDLE_TIMEOUT", value: "a month"},
-	}
-
-	for _, test := range tests {
-		t.Run(test.key, func(t *testing.T) {
-			t.Setenv(test.key, test.value)
-
-			_, err := loadConfig(t)
-			if err == nil {
-				t.Fatalf("%s=%q: got no error", test.key, test.value)
-			}
-
-			msg := err.Error()
-			if !strings.Contains(msg, test.key) ||
-				!strings.Contains(msg, test.value) {
-				t.Errorf("error %q does not name %s and %q",
-					msg, test.key, test.value)
-			}
-		})
-	}
-}
-
 func TestIRCListenAddrUnsetKeepsDefault(t *testing.T) {
 	// t.Setenv puts back whatever value was there after the test.
 	t.Setenv("IRC_LISTEN_ADDR", "")