// Package config handles loading and validating the KeyCape server configuration
// from a YAML file. The config path is resolved from the --config flag or the
// KEYCAPE_CONFIG environment variable.
package config

import (
	"fmt"
	"os"
	"time"

	"gopkg.in/yaml.v3"

	"keycape/internal/adapters/authelia"
	"keycape/internal/adapters/lldap"
	"keycape/internal/adapters/privacyidea"
	"keycape/internal/domain"
)

// Config is the top-level server configuration.
type Config struct {
	Issuer        string             `yaml:"issuer"`
	Port          int                `yaml:"port"`
	TokenLifetime string             `yaml:"tokenLifetime"`
	PrivateKeyPEM string             `yaml:"privateKeyPem"`
	LLDAP         lldap.Config       `yaml:"lldap"`
	Authelia      authelia.Config    `yaml:"authelia"`
	PrivacyIDEA   privacyidea.Config `yaml:"privacyidea"`
	Clients       []ClientConfig     `yaml:"clients"`
	Environment   string             `yaml:"environment"`
	TenantEngine  TenantEngineConfig `yaml:"tenantEngine,omitempty"`
}

// TenantEngineConfig configures the optional tenant_roles cache claim.
//
// Opt-in by design: an empty baseURL leaves the claim off entirely, which is
// what the stock server does. tenant_roles is a cache callers must not trust for
// privileged decisions, and the adapter fails open, so enabling it is a
// performance choice rather than a security one (KEY-WP-0024).
type TenantEngineConfig struct {
	// BaseURL is tenant-engine's cache-read endpoint. Empty disables the claim.
	BaseURL string `yaml:"baseURL,omitempty"`

	// Timeout bounds the lookup, which sits on the synchronous token-issuance
	// path. Empty uses the adapter's own short default.
	Timeout string `yaml:"timeout,omitempty"`
}

// ClientConfig is a static OIDC client registration.
type ClientConfig struct {
	ClientID        string   `yaml:"clientId"`
	Audience        string   `yaml:"audience,omitempty"`
	DisplayName     string   `yaml:"displayName"`
	RedirectURIs    []string `yaml:"redirectUris"`
	AllowedScopes   []string `yaml:"allowedScopes"`
	GrantTypes      []string `yaml:"grantTypes"`
	ClientType      string   `yaml:"clientType"` // "confidential" | "public"
	SecretRef       string   `yaml:"secretRef,omitempty"`
	ServiceSubject  string   `yaml:"serviceSubject,omitempty"`
	Tenant          string   `yaml:"tenant,omitempty"`
	Roles           []string `yaml:"roles,omitempty"`
	TokenLifetime   string   `yaml:"tokenLifetime,omitempty"`
	MFARequired     *bool    `yaml:"mfaRequired,omitempty"`
	RegistrationURL string   `yaml:"registrationUrl,omitempty"`
	EnrollmentURL   string   `yaml:"enrollmentUrl,omitempty"`
}

// Load reads and parses the YAML config file at path.
// If path is empty, it falls back to the KEYCAPE_CONFIG environment variable.
// Returns an error if the file cannot be read or parsed.
func Load(path string) (*Config, error) {
	if path == "" {
		path = os.Getenv("KEYCAPE_CONFIG")
	}
	if path == "" {
		return nil, fmt.Errorf("config: no config path specified (use --config or KEYCAPE_CONFIG)")
	}

	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("config: read %q: %w", path, err)
	}

	var cfg Config
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("config: parse %q: %w", path, err)
	}

	return &cfg, nil
}

// Registrations converts the configured clients to domain registrations without
// resolving any secret. Migration and inspection tooling needs the registration
// contract — grants, audience, tenant, roles, lifetime, MFA and handoff policy —
// but must never load secret material, so ClientSecret is deliberately left
// empty here. The server has its own conversion that does resolve secrets.
//
// An unparseable tokenLifetime is an error rather than a silent zero: a
// migration that quietly drops a per-client lifetime is the class of defect this
// exists to avoid.
func (c *Config) Registrations() ([]domain.Client, error) {
	clients := make([]domain.Client, 0, len(c.Clients))
	for _, cc := range c.Clients {
		var lifetime time.Duration
		if cc.TokenLifetime != "" {
			parsed, err := time.ParseDuration(cc.TokenLifetime)
			if err != nil {
				return nil, fmt.Errorf("config: client %q tokenLifetime is invalid: %w", cc.ClientID, err)
			}
			lifetime = parsed
		}
		clients = append(clients, domain.Client{
			ClientID:        cc.ClientID,
			DisplayName:     cc.DisplayName,
			RedirectURIs:    cc.RedirectURIs,
			AllowedScopes:   cc.AllowedScopes,
			GrantTypes:      cc.GrantTypes,
			ClientType:      cc.ClientType,
			SecretRef:       cc.SecretRef,
			Audience:        cc.Audience,
			ServiceSubject:  cc.ServiceSubject,
			Tenant:          cc.Tenant,
			Roles:           cc.Roles,
			TokenLifetime:   lifetime,
			MFARequired:     cc.MFARequired,
			RegistrationURL: cc.RegistrationURL,
			EnrollmentURL:   cc.EnrollmentURL,
		})
	}
	return clients, nil
}