// Package settings persists the daemon's user-editable configuration as a single
// JSON file (~/.keel/settings.json), parallel to the store snapshot. It is a
// leaf type package: it imports nothing else in the app so any layer may depend
// on the Settings value without pulling in adapters.
package settings

import (
	"encoding/json"
	"errors"
	"os"
	"path/filepath"
	"strconv"
)

// ErrInvalidBackend marks a settings value whose ai_backend is not a known
// backend. The applier returns it (wrapped) so the HTTP layer can map it to 400
// without importing the ai package.
var ErrInvalidBackend = errors.New("settings: invalid ai backend")

// ErrInvalidAmbientMode marks a settings value whose ambient_mode is not a
// known mode. The applier returns it (wrapped) so the HTTP layer can map it to
// 400 without importing the ambient package.
var ErrInvalidAmbientMode = errors.New("settings: invalid ambient mode")

// Ambient mode dial values.
const (
	AmbientOff    = "off"
	AmbientStatus = "status"
	AmbientNotify = "notify"
)

// ValidAmbientMode reports whether m is a known ambient mode constant.
func ValidAmbientMode(m string) bool {
	switch m {
	case AmbientOff, AmbientStatus, AmbientNotify:
		return true
	}
	return false
}

// Settings is the user-editable configuration. Field names mirror the env vars
// they replace: KEEL_AI_BACKEND, KEEL_MARVIN_CMD, KEEL_KNOWLEDGE_FILE, KEEL_AW_URL.
type Settings struct {
	AIBackend          string `json:"ai_backend"`
	MarvinCmd          string `json:"marvin_cmd"`
	KnowledgePath      string `json:"knowledge_path"`
	AWURL              string `json:"aw_url"`
	AmbientMode        string `json:"ambient_mode"`
	AmbientCadenceSecs int    `json:"ambient_cadence_secs"`
}

// DefaultPath returns ~/.keel/settings.json.
func DefaultPath() (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(home, ".keel", "settings.json"), nil
}

// Load reads a settings file. A missing file is an error; callers treat that as
// "first run" and seed instead.
func Load(path string) (Settings, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return Settings{}, err
	}
	var s Settings
	if err := json.Unmarshal(data, &s); err != nil {
		return Settings{}, err
	}
	return s, nil
}

// Save writes settings atomically (temp file + rename), creating the directory
// if needed. Mirrors store.Save.
func Save(path string, s Settings) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	data, err := json.MarshalIndent(s, "", "  ")
	if err != nil {
		return err
	}
	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, data, 0o644); err != nil {
		return err
	}
	return os.Rename(tmp, path)
}

// SeedFromEnv builds a Settings from the KEEL_* env vars, applying
// the same defaults the daemon used before the settings file existed. An unset
// AI backend defaults to "claude" (matching ai.NewBackend("")).
func SeedFromEnv() Settings {
	backend := os.Getenv("KEEL_AI_BACKEND")
	if backend == "" {
		backend = "claude"
	}
	awURL := os.Getenv("KEEL_AW_URL")
	if awURL == "" {
		awURL = "http://localhost:5600"
	}
	ambientMode := os.Getenv("KEEL_AMBIENT_MODE")
	if ambientMode == "" {
		ambientMode = AmbientNotify
	}
	ambientCadenceSecs := 300
	if v := os.Getenv("KEEL_AMBIENT_CADENCE_SECS"); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 {
			ambientCadenceSecs = n
		}
	}
	return Settings{
		AIBackend:          backend,
		MarvinCmd:          os.Getenv("KEEL_MARVIN_CMD"),
		KnowledgePath:      os.Getenv("KEEL_KNOWLEDGE_FILE"),
		AWURL:              awURL,
		AmbientMode:        ambientMode,
		AmbientCadenceSecs: ambientCadenceSecs,
	}
}