// Package config loads glint's TOML configuration, falling back to defaults.
package config

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"github.com/BurntSushi/toml"
)

// Config holds the user-tunable settings glint reads at startup.
type Config struct {
	VaultDir     string `toml:"vault_dir"`
	DailySubdir  string `toml:"daily_subdir"`
	DailyFormat  string `toml:"daily_format"`
	GlamourStyle string `toml:"glamour_style"`
	Theme        string `toml:"theme"`
	InboxDir     string `toml:"inbox_dir"`
}

// Default returns the built-in configuration used when no file is present. The
// vault defaults to $GLINT_VAULT, or the current working directory when that is
// unset — a config-file vault_dir (applied in loadFromFile) overrides both.
func Default() Config {
	vault := os.Getenv("GLINT_VAULT")
	if vault == "" {
		if wd, err := os.Getwd(); err == nil {
			vault = wd
		}
	}
	return Config{
		VaultDir:    vault,
		DailySubdir: "Daily",
		DailyFormat: "2006-01-02",
		Theme:       "auto",
	}
}

// Load reads ~/.config/glint/config.toml and overlays it onto the defaults.
func Load() (Config, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return Default(), nil
	}
	return loadFromFile(filepath.Join(home, ".config", "glint", "config.toml"))
}

// loadFromFile is the testable core of Load. A missing file yields the
// defaults with no error; a malformed file yields the defaults plus an error.
func loadFromFile(path string) (Config, error) {
	cfg := Default()
	data, err := os.ReadFile(path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return cfg, nil // absent config is fine
		}
		return cfg, fmt.Errorf("read %s: %w", path, err)
	}
	var fileCfg Config
	if _, err := toml.Decode(string(data), &fileCfg); err != nil {
		return cfg, fmt.Errorf("parse %s: %w", path, err)
	}
	if fileCfg.VaultDir != "" {
		cfg.VaultDir = fileCfg.VaultDir
	}
	if fileCfg.DailySubdir != "" {
		cfg.DailySubdir = fileCfg.DailySubdir
	}
	if fileCfg.DailyFormat != "" {
		cfg.DailyFormat = fileCfg.DailyFormat
	}
	if fileCfg.GlamourStyle != "" {
		cfg.GlamourStyle = fileCfg.GlamourStyle
	}
	if fileCfg.Theme != "" {
		cfg.Theme = fileCfg.Theme
	}
	if fileCfg.InboxDir != "" {
		cfg.InboxDir = fileCfg.InboxDir
	}
	return cfg, nil
}

// InboxRoot is the directory new notes default into: the vault root when
// InboxDir is empty, an absolute InboxDir as-is, or InboxDir resolved under the
// vault when relative.
func (c Config) InboxRoot() string {
	if c.InboxDir == "" {
		return c.VaultDir
	}
	if filepath.IsAbs(c.InboxDir) {
		return c.InboxDir
	}
	return filepath.Join(c.VaultDir, c.InboxDir)
}

// DailyPath builds the absolute path to the daily note for time t.
func (c Config) DailyPath(t time.Time) string {
	return filepath.Join(c.VaultDir, c.DailySubdir, t.Format(c.DailyFormat)+".md")
}