// Package config loads an ntfy client.yml plus command-line overrides.
package config

import (
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"gopkg.in/yaml.v3"
)

// DefaultPath is the per-user ntfy client config used by the official CLI.
func DefaultPath() string {
	home, err := os.UserHomeDir()
	if err != nil {
		return ""
	}
	return filepath.Join(home, ".config", "ntfy", "client.yml")
}

// Auth is sent as a Bearer token or HTTP basic credentials.
// A token wins when both are set. Values are never formatted into errors.
type Auth struct {
	Token    string
	User     string
	Password string
}

// Equal reports whether two credential sets would produce the same header.
func (a Auth) Equal(b Auth) bool {
	return a.Token == b.Token && a.User == b.User && a.Password == b.Password
}

// Apply sets Authorization. A token is sent as Bearer; otherwise basic auth is used.
func (a Auth) Apply(req *http.Request) {
	if a.Token != "" {
		req.Header.Set("Authorization", "Bearer "+a.Token)
		return
	}
	if a.User != "" || a.Password != "" {
		req.SetBasicAuth(a.User, a.Password)
	}
}

// Sub is one topic the TUI should subscribe to.
type Sub struct {
	Origin  string
	Name    string
	Display string
	Auth    Auth
}

// Label is the sidebar text for this topic.
func (s Sub) Label() string {
	if strings.TrimSpace(s.Display) != "" {
		return s.Display
	}
	return s.Name
}

// App is the resolved runtime configuration.
type App struct {
	Since         string
	DefaultHost   string
	Auth          Auth
	Subs          []Sub
	StartupStatus string
}

// Options are CLI inputs. PathSet reports whether --config was passed.
type Options struct {
	Path    string
	PathSet bool
	Host    string
	Token   string
	User    string
	Since   string
	Topics  []string
}

type fileConfig struct {
	DefaultHost     string    `yaml:"default-host"`
	DefaultToken    string    `yaml:"default-token"`
	DefaultUser     string    `yaml:"default-user"`
	DefaultPassword string    `yaml:"default-password"`
	Subscribe       []fileSub `yaml:"subscribe"`
}

type fileSub struct {
	Topic    string  `yaml:"topic"`
	Token    *string `yaml:"token"`
	User     *string `yaml:"user"`
	Password *string `yaml:"password"`
}

// Load reads client.yml when it exists and applies CLI overrides.
// Positional topics replace the file's subscribe list.
func Load(opt Options) (App, error) {
	path := opt.Path
	if path == "" {
		path = DefaultPath()
	}
	var file fileConfig
	data, err := os.ReadFile(path)
	switch {
	case err == nil:
		if err := yaml.Unmarshal(data, &file); err != nil {
			return App{}, fmt.Errorf("parse %s: %w", path, err)
		}
	case os.IsNotExist(err) && !opt.PathSet:
		// A missing default file is fine when topics are passed explicitly.
	case err != nil:
		return App{}, fmt.Errorf("read config: %w", err)
	}

	host := first(opt.Host, file.DefaultHost)
	auth := Auth{
		Token:    file.DefaultToken,
		User:     file.DefaultUser,
		Password: file.DefaultPassword,
	}
	if opt.Token != "" {
		auth.Token = opt.Token
	}
	if opt.User != "" {
		auth.User, auth.Password = splitUser(opt.User)
		auth.Token = ""
	}
	if auth.Token != "" {
		auth.User, auth.Password = "", ""
	}

	since := opt.Since
	if since == "" {
		since = "all"
	}

	specs := file.Subscribe
	if len(opt.Topics) > 0 {
		specs = make([]fileSub, len(opt.Topics))
		for i, topic := range opt.Topics {
			specs[i].Topic = topic
		}
	}
	if len(specs) == 0 {
		if strings.TrimSpace(host) == "" {
			return App{}, fmt.Errorf("no topic given and no default-host in %s", path)
		}
		return App{Since: since, DefaultHost: host, Auth: auth}, nil
	}

	subs := make([]Sub, 0, len(specs))
	for _, spec := range specs {
		origin, name, err := Resolve(spec.Topic, host)
		if err != nil {
			return App{}, err
		}
		subAuth := auth
		if spec.Token != nil {
			subAuth = Auth{Token: *spec.Token}
		}
		if spec.User != nil {
			pass := ""
			if spec.Password != nil {
				pass = *spec.Password
			}
			subAuth = Auth{User: *spec.User, Password: pass}
		}
		subs = append(subs, Sub{Origin: origin, Name: name, Auth: subAuth})
	}

	return App{
		Since:       since,
		DefaultHost: host,
		Auth:        auth,
		Subs:        subs,
	}, nil
}

// MergeSubs appends topics that are not already in base, compared by origin and name.
func MergeSubs(base, extra []Sub) []Sub {
	out := append([]Sub(nil), base...)
	seen := map[string]bool{}
	for _, sub := range out {
		seen[sub.Origin+"\n"+sub.Name] = true
	}
	for _, sub := range extra {
		key := sub.Origin + "\n" + sub.Name
		if seen[key] {
			continue
		}
		seen[key] = true
		out = append(out, sub)
	}
	return out
}

func first(vals ...string) string {
	for _, v := range vals {
		if strings.TrimSpace(v) != "" {
			return strings.TrimSpace(v)
		}
	}
	return ""
}

func splitUser(s string) (string, string) {
	user, pass, ok := strings.Cut(s, ":")
	if !ok {
		return user, ""
	}
	return user, pass
}