nasin/config/config.go

160 lines
5.4 KiB
Go

// Package config provides a configuration system for applications.
package config
import "fmt"
import "math"
import "strconv"
import "git.tebibyte.media/tomo/tomo/event"
type configError string;
func (err configError) Error () string { return string(err) }
const (
// ErrClosed is returned when Get/Set/Reset is called after the config
// has been closed.
ErrClosed = configError("attempt to access a closed config")
// ErrNonexistentEntry is returned when an entry was not found.
ErrNonexistentEntry = configError("nonexistent entry")
// ErrMalformedEntry is returned when a config entry could not be
// parsed.
ErrMalformedEntry = configError("malformed entry")
// ErrMalformedKey is returned when a key has invalid runes.
ErrMalformedKey = configError("malformed key")
// ErrMalformedValue is returned when a value could not be parsed.
ErrMalformedValue = configError("malformed value")
// ErrMalformedString is returned when a string value could not be
// parsed.
ErrMalformedStringValue = configError("malformed string value")
// ErrMalformedNumber is returned when a number value could not be
// parsed.
ErrMalformedNumberValue = configError("malformed number value")
// ErrMalformedBool is returned when a boolean value could not be
// parsed.
ErrMalformedBoolValue = configError("malformed bool value")
// ErrMalformedEscapeSequence us returned when an escape sequence could
// not be parsed.
ErrMalformedEscapeSequence = configError("malformed escape sequence")
)
// Config provides access to an application's configuration, and can notify an
// application of changes to it.
type Config interface {
// Get gets a value, first considering the user-level config file, and
// then falling back to system level config files. If the value could
// not be found anywhere, the specified fallback value is returned. If
// the key is invalid, it returns nil, ErrMalformedKey.
Get (key string, fallback Value) (Value, error)
// GetString is like Get, but will only return strings. If the value is
// not a string, it will return fallback.
GetString (key string, fallback string) (string, error)
// GetNumber is like Get, but will only return numbers. If the value is
// not a number, it will return fallback.
GetNumber (key string, fallback float64) (float64, error)
// GetBool is like Get, but will only return booleans. If the value is
// not a boolean, it will return fallback.
GetBool (key string, fallback bool) (bool, error)
// Set sets a value in the user-level config file. If the key is
// invalid, it returns ErrMalformedKey. Note that calling this behavior
// *will* cause a write to disk, and a read from disk for whatever is
// watching the user file.
Set (key string, value Value) error
// Reset removes the value from the user-level config file, resetting it
// to what is described by the system-level config files. If the key is
// invalid, it returns ErrMalformedKey. Note that calling this behavior
// *will* cause a write to disk if successful , and a read from disk for
// whatever is watching the user file.
Reset (key string) error
// OnChange specifies a function to be called whenever a value is
// changed. The callback is always run within the backend's event loop
// using tomo.Do. This could have been a channel but I didn't want to do
// that to people.
OnChange (func (key string)) event.Cookie
}
// ConfigCloser is a config with a Close behavior, which stops watching the
// config file and causes any subsequent sets/gets to return errors. Anything
// that receives a ConfigCloser must close it when done.
type ConfigCloser interface {
Config
// Close closes the config, causing it to stop watching for changes.
// Reads or writes to the config after this will return an error.
Close () error
}
var negativeZero = math.Copysign(0, -1)
// Value is a config value. Its String behavior produces a lossless and
// syntactically valid representation of the value.
type Value interface {
value ()
fmt.Stringer
Equals (Value) bool
}
// ValueString is a string value.
type ValueString string
var _ Value = ValueString("")
func (ValueString) value () { }
func (value ValueString) Equals (other Value) bool {
other, ok := other.(ValueString)
return ok && value == other
}
func (value ValueString) String () string {
return fmt.Sprintf("\"%s\"", escape(string(value)))
}
// ValueNumber is a number value.
type ValueNumber float64
var _ Value = ValueNumber(0)
func (ValueNumber) value () { }
func (value ValueNumber) Equals (other Value) bool {
other, ok := other.(ValueNumber)
return ok && value == other
}
func (value ValueNumber) String () string {
number := float64(value)
// the requirements I wrote said lossless in all cases. here's lossless
// in all cases!
switch {
case math.IsInf(number, 0):
if math.Signbit(number) {
return "-Inf"
} else {
return "Inf"
}
case math.IsNaN(number):
return "NaN"
case number == 0, number == negativeZero:
if math.Signbit(number) {
return "-0"
} else {
return "0"
}
case math.Round(number) == number:
return strconv.FormatInt(int64(number), 10)
default:
return strconv.FormatFloat(number, 'f', -1, 64)
}
}
// ValueBool is a boolean value.
var _ Value = ValueBool(false)
type ValueBool bool
func (ValueBool) value () { }
func (value ValueBool) Equals (other Value) bool {
other, ok := other.(ValueBool)
return ok && value == other
}
func (value ValueBool) String () string {
if value {
return "true"
} else {
return "false"
}
}