// 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"` // the vault `glint -v` opens from anywhere
	DailySubdir  string `toml:"daily_subdir"`
	DailyFormat  string `toml:"daily_format"`
	GlamourStyle string `toml:"glamour_style"`
	Theme        string `toml:"theme"`
	InboxDir     string `toml:"inbox_dir"`
	Spellcheck   string `toml:"spellcheck"` // auto | on | off (TASK-020)

	// PDF/printable export fonts (TASK-021). CSS font-family stacks that
	// override the house-style --font-* tokens. Defaults are portable
	// open/system faces — glint ships to people without the kit's licensed
	// fonts, so nothing licensed is baked in.
	FontDisplay string `toml:"font_display"` // headings / cover
	FontBody    string `toml:"font_body"`    // body prose
	FontMono    string `toml:"font_mono"`    // code
}

// Default returns the built-in configuration used when no file is present.
// VaultDir is empty by default: bare glint works in the current directory; set
// vault_dir (config) to give `glint -v` a fixed vault to open from anywhere.
func Default() Config {
	return Config{
		DailySubdir: "Daily",
		DailyFormat: "2006-01-02",
		Theme:       "auto",
		Spellcheck:  "auto",
		FontDisplay: "Georgia, \"Times New Roman\", serif",
		FontBody:    "system-ui, -apple-system, BlinkMacSystemFont, \"Segoe UI\", Roboto, sans-serif",
		FontMono:    "ui-monospace, SFMono-Regular, Menlo, Consolas, monospace",
	}
}

// WorkingDir is where bare `glint`, `glint -n`, and `-d` operate: the
// $GLINT_VAULT pin if set, otherwise the current working directory.
func (c Config) WorkingDir() string {
	if v := os.Getenv("GLINT_VAULT"); v != "" {
		return v
	}
	if wd, err := os.Getwd(); err == nil {
		return wd
	}
	return "."
}

// Vault is the directory `glint -v` opens from anywhere: the configured
// vault_dir, or the working directory when none is set.
func (c Config) Vault() string {
	if c.VaultDir != "" {
		return c.VaultDir
	}
	return c.WorkingDir()
}

// Path is the config file location: ~/.config/glint/config.toml.
func Path() string {
	home, err := os.UserHomeDir()
	if err != nil {
		return filepath.Join(".config", "glint", "config.toml")
	}
	return filepath.Join(home, ".config", "glint", "config.toml")
}

// DictPath is the personal spellcheck dictionary location:
// ~/.config/glint/dict.txt (TASK-020).
func DictPath() string {
	home, err := os.UserHomeDir()
	if err != nil {
		return filepath.Join(".config", "glint", "dict.txt")
	}
	return filepath.Join(home, ".config", "glint", "dict.txt")
}

// Load reads the config file and overlays it onto the defaults.
func Load() (Config, error) {
	return loadFromFile(Path())
}

// Save writes cfg to path as TOML, creating the parent directory.
func Save(cfg Config, path string) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	f, err := os.Create(path)
	if err != nil {
		return err
	}
	if err := toml.NewEncoder(f).Encode(cfg); err != nil {
		_ = f.Close()
		return err
	}
	return f.Close()
}

// 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
	}
	if fileCfg.Spellcheck != "" {
		cfg.Spellcheck = fileCfg.Spellcheck
	}
	if fileCfg.FontDisplay != "" {
		cfg.FontDisplay = fileCfg.FontDisplay
	}
	if fileCfg.FontBody != "" {
		cfg.FontBody = fileCfg.FontBody
	}
	if fileCfg.FontMono != "" {
		cfg.FontMono = fileCfg.FontMono
	}
	return cfg, nil
}

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

// DailyDir is the folder daily notes live in (for the daily-folder picker): an
// absolute daily_subdir as-is, else daily_subdir under the vault.
func (c Config) DailyDir() string {
	if filepath.IsAbs(c.DailySubdir) {
		return c.DailySubdir
	}
	return filepath.Join(c.Vault(), c.DailySubdir)
}

// DailyPath builds the path to the daily note for time t. Daily notes belong to
// the vault (Vault()), not the working directory, so `glint --daily` lands in
// the same place from anywhere. An absolute daily_subdir is used as-is.
func (c Config) DailyPath(t time.Time) string {
	name := t.Format(c.DailyFormat) + ".md"
	if filepath.IsAbs(c.DailySubdir) {
		return filepath.Join(c.DailySubdir, name)
	}
	return filepath.Join(c.Vault(), c.DailySubdir, name)
}