package ovh

import (
	"context"
	"errors"
	"fmt"
	"os"
	"os/user"
	"strings"

	"golang.org/x/oauth2/clientcredentials"
	"gopkg.in/ini.v1"
)

var configPaths = []string{
	// System wide configuration
	"/etc/ovh.conf",
	// Configuration in user's home
	"~/.ovh.conf",
	// Configuration in local folder
	"./ovh.conf",
}

// currentUserHome attempts to get current user's home directory.
func currentUserHome() (string, error) {
	usr, err := user.Current()
	if err != nil {
		// Fallback by trying to read $HOME
		if userHome := os.Getenv("HOME"); userHome != "" {
			return userHome, nil
		}
		return "", err
	}

	return usr.HomeDir, nil
}

// configPaths returns configPaths, with ~/ prefix expanded.
func expandConfigPaths() []interface{} {
	paths := []interface{}{}

	// Will be initialized on first use
	var home string
	var homeErr error

	for _, path := range configPaths {
		if strings.HasPrefix(path, "~/") {
			// Find home if needed
			if home == "" && homeErr == nil {
				home, homeErr = currentUserHome()
			}
			// Ignore file in HOME if we cannot find it
			if homeErr != nil {
				continue
			}

			path = home + path[1:]
		}

		paths = append(paths, path)
	}

	return paths
}

// loadINI builds a ini.File from the configuration paths provided in configPaths.
// It's a helper for loadConfig.
func loadINI() (*ini.File, error) {
	paths := expandConfigPaths()
	if len(paths) == 0 {
		return ini.Empty(), nil
	}

	return ini.LooseLoad(paths[0], paths[1:]...)
}

// loadConfig loads client configuration from params, environments or configuration
// files (by order of decreasing precedence).
//
// loadConfig will check OVH_CONSUMER_KEY, OVH_APPLICATION_KEY, OVH_APPLICATION_SECRET
// and OVH_ENDPOINT environment variables. If any is present, it will take precedence
// over any configuration from file.
//
// Configuration files are ini files. They share the same format as python-ovh,
// node-ovh, php-ovh and all other wrappers. If any wrapper is configured, all
// can re-use the same configuration. loadConfig will check for configuration in:
//
// - ./ovh.conf
// - $HOME/.ovh.conf
// - /etc/ovh.conf
func (c *Client) loadConfig(endpointName string) error {
	if strings.HasSuffix(endpointName, "/") {
		return fmt.Errorf("endpoint name cannot have a tailing slash")
	}

	// Load configuration files by order of increasing priority. All configuration
	// files are optional. Only load file from user home if home could be resolve
	cfg, err := loadINI()
	if err != nil {
		return fmt.Errorf("cannot load configuration: %w", err)
	}

	// Canonicalize configuration
	if endpointName == "" {
		endpointName = getConfigValue(cfg, "default", "endpoint", "ovh-eu")
	}

	if c.AccessToken == "" {
		c.AccessToken = getConfigValue(cfg, endpointName, "access_token", "")
	}

	if c.AppKey == "" {
		c.AppKey = getConfigValue(cfg, endpointName, "application_key", "")
	}

	if c.AppSecret == "" {
		c.AppSecret = getConfigValue(cfg, endpointName, "application_secret", "")
	}

	if c.ConsumerKey == "" {
		c.ConsumerKey = getConfigValue(cfg, endpointName, "consumer_key", "")
	}

	if c.ClientID == "" {
		c.ClientID = getConfigValue(cfg, endpointName, "client_id", "")
	}

	if c.ClientSecret == "" {
		c.ClientSecret = getConfigValue(cfg, endpointName, "client_secret", "")
	}

	configuredAuthMethods := []string{}
	if c.AppKey != "" || c.AppSecret != "" || c.ConsumerKey != "" {
		configuredAuthMethods = append(configuredAuthMethods, "application_key/application_secret")
	}
	if c.ClientID != "" || c.ClientSecret != "" {
		configuredAuthMethods = append(configuredAuthMethods, "client_id/client_secret")
	}
	if c.AccessToken != "" {
		configuredAuthMethods = append(configuredAuthMethods, "access_token")
	}

	if len(configuredAuthMethods) > 1 {
		return fmt.Errorf("can't use multiple authentication methods: %s", strings.Join(configuredAuthMethods, ", "))
	}
	if len(configuredAuthMethods) == 0 {
		return errors.New(
			"missing authentication information, you need to provide one of the following: application_key/application_secret, client_id/client_secret, or access_token",
		)
	}

	if (c.ClientID != "") != (c.ClientSecret != "") {
		return errors.New("invalid oauth2 config, both client_id and client_secret must be given")
	}
	if (c.AppKey != "") != (c.AppSecret != "") {
		return errors.New("invalid authentication config, both application_key and application_secret must be given")
	}

	// Load real endpoint URL by name. If endpoint contains a '/', consider it as a URL
	if strings.Contains(endpointName, "/") {
		c.endpoint = endpointName
	} else {
		c.endpoint = Endpoints[endpointName]
	}

	// If we still have no valid endpoint, AppKey or AppSecret, return an error
	if c.endpoint == "" {
		return fmt.Errorf("unknown endpoint '%s', consider checking 'Endpoints' list or using an URL", endpointName)
	}

	if c.ClientID != "" {
		if _, ok := tokensURLs[c.endpoint]; !ok {
			return fmt.Errorf("oauth2 authentication is not compatible with endpoint %q", c.endpoint)
		}

		conf := &clientcredentials.Config{
			ClientID:     c.ClientID,
			ClientSecret: c.ClientSecret,
			TokenURL:     tokensURLs[c.endpoint],
			Scopes:       []string{"all"},
		}

		c.oauth2TokenSource = conf.TokenSource(context.Background())
	}

	return nil
}

// getConfigValue returns the value of OVH_<NAME> or "name" value from "section". If
// the value could not be read from either env or any configuration files, return 'def'
func getConfigValue(cfg *ini.File, section, name, def string) string {
	// Attempt to load from environment
	fromEnv := os.Getenv("OVH_" + strings.ToUpper(name))
	if len(fromEnv) > 0 {
		return fromEnv
	}

	// Attempt to load from configuration
	fromSection := cfg.Section(section)
	if fromSection == nil {
		return def
	}

	fromSectionKey := fromSection.Key(name)
	if fromSectionKey == nil {
		return def
	}
	return fromSectionKey.String()
}
