package config

import (
	"fmt"
	"os"
	"time"

	"forgejo.riotpiao.com/rock/homelab-frontend/internal/serviceadapter"
)

// Config holds the gateway configuration.
type Config struct {
	// ListenAddr is the address to listen on for HTTP traffic.
	ListenAddr string
	// ShutdownTimeout is the maximum time to wait for in-flight requests
	// to complete before forcing shutdown.
	ShutdownTimeout time.Duration
	// Routes maps route names to their upstream configuration.
	Routes map[string]*Route
	// Models maps model names to their upstream configuration.
	// Multiple models can point to the same upstream address.
	Models map[string]*ModelUpstream
	// Adapters holds service adapter definitions for X-Service routing.
	Adapters []*serviceadapter.ServiceAdapter
	// Auth holds JWT authentication configuration for /v1/* endpoints.
	Auth AuthConfig
}

// ModelUpstream holds upstream configuration for a specific model.
type ModelUpstream struct {
	// Name is the model name clients send (e.g., "reasoning", "ornith:35b").
	Name string
	// Address is the upstream server address (host:port).
	Address string
	// Path is the upstream path for this model (e.g., "/v1/chat/completions").
	Path string
	// AuthRequired indicates whether this model requires JWT authentication.
	AuthRequired bool
}

// AuthConfig holds JWT authentication configuration.
type AuthConfig struct {
	// Enabled globally enables/disables auth for /v1/* endpoints.
	Enabled bool
	// Issuer is the expected JWT issuer (iss claim).
	Issuer string
	// Audience is the expected JWT audience (aud claim).
	Audience string
	// JWKSURL is the URL to fetch JSON Web Key Set for signature validation.
	JWKSURL string
	// RequiredCapability is the permission required for LLM inference (e.g., "llm:inference").
	RequiredCapability string
}

// Route represents a single route and its upstream configuration.
type Route struct {
	// Name is the route identifier.
	Name string
	// Upstream holds the upstream server configuration.
	Upstream Upstream
}

// Upstream holds upstream server configuration for a route.
type Upstream struct {
	// Address is the upstream server address (host:port).
	Address string
	// PathRewrite is an optional path prefix rewrite. Empty string means no rewrite.
	PathRewrite string
	// ConnectTimeout is the maximum time to establish a connection to the upstream.
	ConnectTimeout time.Duration
	// ReadTimeout is the maximum time to read a response from the upstream.
	ReadTimeout time.Duration
	// WriteTimeout is the maximum time to write a request to the upstream.
	WriteTimeout time.Duration
	// MaxBodySize is the maximum request body size in bytes.
	MaxBodySize int64
	// AuthRequired indicates whether this route requires authentication.
	AuthRequired bool
}

// LookupModel finds a model by name (case-sensitive, exact match).
func (c *Config) LookupModel(name string) *ModelUpstream {
	if c == nil || c.Models == nil {
		return nil
	}
	return c.Models[name]
}

// ModelNames returns a sorted list of all known model names.
func (c *Config) ModelNames() []string {
	if c == nil || c.Models == nil {
		return nil
	}
	names := make([]string, 0, len(c.Models))
	for name := range c.Models {
		names = append(names, name)
	}
	return names
}

// Load reads configuration from environment variables with defaults.
func Load() (*Config, error) {
	listenAddr := "127.0.0.1:8080"
	// Allow override via environment variable
	if addr, ok := os.LookupEnv("LISTEN_ADDR"); ok {
		listenAddr = addr
	}

	shutdownTimeout := 30 * time.Second
	// Allow override via environment variable
	if timeout, ok := os.LookupEnv("SHUTDOWN_TIMEOUT"); ok {
		d, err := time.ParseDuration(timeout)
		if err != nil {
			return nil, fmt.Errorf("invalid SHUTDOWN_TIMEOUT: %w", err)
		}
		shutdownTimeout = d
	}

	// Load routes, models, adapters, and auth from config file
	routes := make(map[string]*Route)
	models := make(map[string]*ModelUpstream)
	var adapters []*serviceadapter.ServiceAdapter
	var authConfig AuthConfig
	if configPath, ok := os.LookupEnv("CONFIG_PATH"); ok {
		loadedRoutes, loadedModels, loadedAdapters, loadedAuth, err := LoadRoutesAndModelsFromFile(configPath)
		if err != nil {
			return nil, err
		}
		routes = loadedRoutes
		models = loadedModels
		adapters = loadedAdapters
		authConfig = loadedAuth
	}

	return &Config{
		ListenAddr:      listenAddr,
		ShutdownTimeout: shutdownTimeout,
		Routes:          routes,
		Models:          models,
		Adapters:        adapters,
		Auth:            authConfig,
	}, nil
}