// Package config loads and validates the arr-tui configuration file.
package config

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"net/url"
	"os"
	"path/filepath"
	"strings"
)

// Service holds the connection settings of a single backend.
type Service struct {
	URL    string `json:"url"`
	APIKey string `json:"apikey"`
}

// Arr is a Radarr or Sonarr instance, with optional defaults for the add form.
type Arr struct {
	Service
	DefaultQualityProfile string `json:"default_quality_profile,omitempty"`
	DefaultRootFolder     string `json:"default_root_folder,omitempty"`
}

// UI holds interface settings.
type UI struct {
	RefreshSeconds int `json:"refresh_seconds,omitempty"`
	// Covers shows poster thumbnails in the detail panes (default true).
	// Posters of titles that are not in the library yet are downloaded from
	// the public image hosts Radarr/Sonarr point to (TMDb, TheTVDB).
	Covers *bool `json:"covers,omitempty"`
	// NotifyDownloads shows a popup (and logs it) when a SABnzbd download
	// finishes or fails, whichever view is open (default true).
	NotifyDownloads *bool `json:"notify_downloads,omitempty"`
	// Bell also rings the terminal bell for those notifications (default false).
	Bell bool `json:"bell,omitempty"`
	// CoverStyle selects the block characters posters are drawn with:
	// "quadrant" (2x2 pixels per cell, every font has the glyphs), "sextant"
	// (2x3, sharper, needs a font with the Symbols for Legacy Computing
	// block, e.g. kitty, WezTerm, foot, Ghostty), "kitty" (real images through
	// the Kitty graphics protocol with Unicode placeholders: kitty and
	// Ghostty) or "auto" (default: the Kitty protocol where the terminal is
	// known to support it, else sextant on terminals known to draw them or when
	// fontconfig finds a font with the glyphs, else quadrant). The block styles are also the fallback for "kitty".
	CoverStyle string `json:"cover_style,omitempty"`
}

// ShouldNotifyDownloads reports whether finished downloads are announced.
func (u UI) ShouldNotifyDownloads() bool { return u.NotifyDownloads == nil || *u.NotifyDownloads }

// ShowCovers reports whether poster thumbnails are enabled.
func (u UI) ShowCovers() bool { return u.Covers == nil || *u.Covers }

// Config is the full application configuration.
type Config struct {
	Radarr  Arr     `json:"radarr"`
	Sonarr  Arr     `json:"sonarr"`
	SABnzbd Service `json:"sabnzbd"`
	UI      UI      `json:"ui"`
}

const defaultRefreshSeconds = 3

// DefaultPath returns $XDG_CONFIG_HOME/arr-tui/config.json, falling back to
// ~/.config/arr-tui/config.json.
func DefaultPath() (string, error) {
	dir := os.Getenv("XDG_CONFIG_HOME")
	if dir == "" {
		home, err := os.UserHomeDir()
		if err != nil {
			return "", err
		}
		dir = filepath.Join(home, ".config")
	}
	return filepath.Join(dir, "arr-tui", "config.json"), nil
}

// Load reads the config at path, applies environment overrides and defaults,
// and validates the result. The returned warnings are non-fatal.
func Load(path string) (*Config, []string, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, nil, fmt.Errorf("reading config: %w", err)
	}

	var warnings []string
	if info, err := os.Stat(path); err == nil && info.Mode().Perm()&0o077 != 0 {
		warnings = append(warnings, fmt.Sprintf(
			"%s is accessible by other users (mode %04o); it contains API keys, consider chmod 600",
			path, info.Mode().Perm()))
	}

	cfg, err := Parse(data)
	if err != nil {
		return nil, nil, fmt.Errorf("%s: %w", path, err)
	}
	return cfg, warnings, nil
}

// Parse decodes config JSON, applies environment overrides and defaults, and
// validates the result. Unknown fields are rejected to catch typos.
func Parse(data []byte) (*Config, error) {
	raw, err := parseRaw(data)
	if err != nil {
		return nil, err
	}
	return raw.Effective(os.Getenv)
}

// parseRaw decodes config JSON as it stands in the file: no environment
// overrides, no defaults, no validation.
func parseRaw(data []byte) (*Config, error) {
	var cfg Config
	dec := json.NewDecoder(bytes.NewReader(data))
	dec.DisallowUnknownFields()
	if err := dec.Decode(&cfg); err != nil {
		return nil, fmt.Errorf("parsing config: %w", err)
	}
	return &cfg, nil
}

// LoadFile reads the config at path exactly as written: no environment
// overrides, no defaults, no validation. It is what an editor of the file must
// start from, so values that only came from the environment are not written
// back to disk.
func LoadFile(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading config: %w", err)
	}
	cfg, err := parseRaw(data)
	if err != nil {
		return nil, fmt.Errorf("%s: %w", path, err)
	}
	return cfg, nil
}

// Effective returns the configuration the program runs with: a copy with the
// environment overrides and defaults applied, validated.
func (c *Config) Effective(env func(string) string) (*Config, error) {
	cfg := *c
	if c.UI.Covers != nil {
		v := *c.UI.Covers
		cfg.UI.Covers = &v
	}
	if c.UI.NotifyDownloads != nil {
		v := *c.UI.NotifyDownloads
		cfg.UI.NotifyDownloads = &v
	}
	cfg.applyEnv(env)
	cfg.applyDefaults()
	if err := cfg.Validate(); err != nil {
		return nil, err
	}
	return &cfg, nil
}

// envVars maps the settings that can be overridden by the environment to the
// variable that does it.
var envVars = map[string]string{
	"radarr.url":     "ARR_TUI_RADARR_URL",
	"radarr.apikey":  "ARR_TUI_RADARR_APIKEY",
	"sonarr.url":     "ARR_TUI_SONARR_URL",
	"sonarr.apikey":  "ARR_TUI_SONARR_APIKEY",
	"sabnzbd.url":    "ARR_TUI_SABNZBD_URL",
	"sabnzbd.apikey": "ARR_TUI_SABNZBD_APIKEY",
}

// Overrides returns, for every setting that the environment currently
// overrides, the name of the variable. Keys look like "radarr.url".
func Overrides(env func(string) string) map[string]string {
	out := map[string]string{}
	for key, name := range envVars {
		if env(name) != "" {
			out[key] = name
		}
	}
	return out
}

// Save writes the config to path as indented JSON. The file is replaced
// atomically (a temporary file in the same directory, then a rename) and keeps
// the permissions of the existing file, or is private (0600) when new: it
// holds API keys.
func Save(path string, cfg *Config) error {
	data, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		return err
	}
	data = append(data, '\n')

	mode := os.FileMode(0o600)
	if info, err := os.Stat(path); err == nil {
		mode = info.Mode().Perm()
	}
	tmp, err := os.CreateTemp(filepath.Dir(path), ".config-*.tmp")
	if err != nil {
		return fmt.Errorf("saving config: %w", err)
	}
	defer os.Remove(tmp.Name()) // no-op after a successful rename
	if err := tmp.Chmod(mode); err != nil {
		tmp.Close()
		return fmt.Errorf("saving config: %w", err)
	}
	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		return fmt.Errorf("saving config: %w", err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("saving config: %w", err)
	}
	if err := os.Rename(tmp.Name(), path); err != nil {
		return fmt.Errorf("saving config: %w", err)
	}
	return nil
}

func (c *Config) applyEnv(get func(string) string) {
	override := func(dst *string, key string) {
		if v := get(key); v != "" {
			*dst = v
		}
	}
	override(&c.Radarr.URL, "ARR_TUI_RADARR_URL")
	override(&c.Radarr.APIKey, "ARR_TUI_RADARR_APIKEY")
	override(&c.Sonarr.URL, "ARR_TUI_SONARR_URL")
	override(&c.Sonarr.APIKey, "ARR_TUI_SONARR_APIKEY")
	override(&c.SABnzbd.URL, "ARR_TUI_SABNZBD_URL")
	override(&c.SABnzbd.APIKey, "ARR_TUI_SABNZBD_APIKEY")
}

func (c *Config) applyDefaults() {
	if c.UI.RefreshSeconds <= 0 {
		c.UI.RefreshSeconds = defaultRefreshSeconds
	}
	c.Radarr.URL = strings.TrimRight(c.Radarr.URL, "/")
	c.Sonarr.URL = strings.TrimRight(c.Sonarr.URL, "/")
	c.SABnzbd.URL = strings.TrimRight(c.SABnzbd.URL, "/")
}

// Validate checks that every service has a usable URL and API key.
func (c *Config) Validate() error {
	var errs []error
	for _, s := range []struct {
		name string
		svc  Service
	}{
		{"radarr", c.Radarr.Service},
		{"sonarr", c.Sonarr.Service},
		{"sabnzbd", c.SABnzbd},
	} {
		if s.svc.APIKey == "" {
			errs = append(errs, fmt.Errorf("%s: apikey is required", s.name))
		}
		u, err := url.Parse(s.svc.URL)
		switch {
		case s.svc.URL == "":
			errs = append(errs, fmt.Errorf("%s: url is required", s.name))
		case err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "":
			errs = append(errs, fmt.Errorf("%s: url %q must be an http(s) URL", s.name, s.svc.URL))
		}
	}
	switch c.UI.CoverStyle {
	case "", "auto", "quadrant", "sextant", "kitty":
	default:
		errs = append(errs, fmt.Errorf(`ui.cover_style: %q must be "auto", "kitty", "sextant" or "quadrant"`, c.UI.CoverStyle))
	}
	return errors.Join(errs...)
}