// Package config loads and validates process configuration.
package config

import (
	"fmt"
	"net/url"
	"os"
	"strconv"
	"strings"
	"time"
	"unicode"
)

const (
	// HTTPAddressEnv is the environment variable used to configure the listen address.
	HTTPAddressEnv = "FIRE_SAFETY_HTTP_ADDR"

	SuperAgentEnabledEnv                = "FIRE_SAFETY_SUPERAGENT_ENABLED"
	SuperAgentBaseURLEnv                = "FIRE_SAFETY_SUPERAGENT_BASE_URL"
	SuperAgentOpenAPIKeyEnv             = "FIRE_SAFETY_SUPERAGENT_OPEN_API_KEY"
	SuperAgentConnectTimeoutEnv         = "FIRE_SAFETY_SUPERAGENT_CONNECT_TIMEOUT"
	SuperAgentRecoveryMaxAttemptsEnv    = "FIRE_SAFETY_SUPERAGENT_RECOVERY_MAX_ATTEMPTS"
	SuperAgentRecoveryInitialBackoffEnv = "FIRE_SAFETY_SUPERAGENT_RECOVERY_INITIAL_BACKOFF"
	SuperAgentMaxMessageBytesEnv        = "FIRE_SAFETY_SUPERAGENT_MAX_MESSAGE_BYTES"
	SuperAgentProbeSubjectIDEnv         = "FIRE_SAFETY_SUPERAGENT_PROBE_SUBJECT_ID"
	SuperAgentProbeTimeoutEnv           = "FIRE_SAFETY_SUPERAGENT_PROBE_TIMEOUT"

	ChatEnabledEnv               = "FIRE_SAFETY_CHAT_ENABLED"
	ChatPageEnabledEnv           = "FIRE_SAFETY_CHAT_PAGE_ENABLED"
	ChatAuthTokenEnv             = "FIRE_SAFETY_CHAT_AUTH_TOKEN"
	ChatAllowLegacyShortTokenEnv = "FIRE_SAFETY_CHAT_ALLOW_LEGACY_SHORT_TOKEN"
	ChatSubjectIDEnv             = "FIRE_SAFETY_CHAT_SUBJECT_ID"
	ChatAllowedOriginsEnv        = "FIRE_SAFETY_CHAT_ALLOWED_ORIGINS"
	ChatMaxBodyBytesEnv          = "FIRE_SAFETY_CHAT_MAX_BODY_BYTES"
	ChatRunTimeoutEnv            = "FIRE_SAFETY_CHAT_RUN_TIMEOUT"
	ChatSessionTTLEnv            = "FIRE_SAFETY_CHAT_SESSION_TTL"
	ChatMaxSessionsEnv           = "FIRE_SAFETY_CHAT_MAX_SESSIONS"
	ChatCompatAppIDEnv           = "FIRE_SAFETY_CHAT_COMPAT_APP_ID"

	MCPEnabledEnv      = "FIRE_SAFETY_MCP_ENABLED"
	MCPAuthTokenEnv    = "FIRE_SAFETY_MCP_AUTH_TOKEN"
	MCPScopeModeEnv    = "FIRE_SAFETY_MCP_SCOPE_MODE"
	MCPAllowedTownsEnv = "FIRE_SAFETY_MCP_ALLOWED_TOWNS"
	MCPMaxBodyBytesEnv = "FIRE_SAFETY_MCP_MAX_BODY_BYTES"
	MCPToolTimeoutEnv  = "FIRE_SAFETY_MCP_TOOL_TIMEOUT"

	PostGISEnabledEnv        = "FIRE_SAFETY_POSTGIS_ENABLED"
	PostGISDSNEnv            = "FIRE_SAFETY_POSTGIS_DSN"
	PostGISExpectedSRIDEnv   = "FIRE_SAFETY_POSTGIS_EXPECTED_SRID"
	PostGISConnectTimeoutEnv = "FIRE_SAFETY_POSTGIS_CONNECT_TIMEOUT"
	PostGISQueryTimeoutEnv   = "FIRE_SAFETY_POSTGIS_QUERY_TIMEOUT"
	PostGISMaxConnsEnv       = "FIRE_SAFETY_POSTGIS_MAX_CONNS"

	defaultHTTPAddress                         = ":8080"
	defaultSuperAgentConnectTimeout            = 15 * time.Second
	defaultSuperAgentRecoveryMaxAttempts       = 5
	maximumSuperAgentRecoveryAttempts          = 20
	defaultSuperAgentRecoveryBackoff           = 250 * time.Millisecond
	defaultSuperAgentMaxMessageBytes     int64 = 64 * 1024
	maximumSuperAgentMessageBytes        int64 = 16 * 1024 * 1024
	defaultSuperAgentProbeSubjectID            = "fire-safety-ymd-connectivity-probe"
	defaultSuperAgentProbeTimeout              = 10 * time.Minute
	defaultChatSubjectID                       = "fire-safety-ymd-chat-test-subject"
	defaultChatMaxBodyBytes              int64 = 128 * 1024
	maximumChatBodyBytes                 int64 = 1024 * 1024
	defaultChatRunTimeout                      = 10 * time.Minute
	maximumChatRunTimeout                      = 30 * time.Minute
	defaultChatSessionTTL                      = 30 * time.Minute
	maximumChatSessionTTL                      = 24 * time.Hour
	defaultChatMaxSessions               int64 = 1000
	maximumChatMaxSessions               int64 = 10_000
	maximumChatAllowedOrigins                  = 50
	defaultMCPMaxBodyBytes               int64 = 256 * 1024
	maximumMCPBodyBytes                  int64 = 1024 * 1024
	defaultMCPToolTimeout                      = 5 * time.Second
	maximumMCPToolTimeout                      = 30 * time.Second
	defaultMCPScopeMode                        = MCPScopeModeTownAllowlist
	defaultPostGISConnectTimeout               = 5 * time.Second
	defaultPostGISQueryTimeout                 = 3 * time.Second
	maximumPostGISTimeout                      = 30 * time.Second
	defaultPostGISMaxConns               int64 = 4
	maximumPostGISMaxConns               int64 = 20
	requiredMCPSpatialSRID                     = 4326
)

// MCPScopeMode defines the trusted server-side data scope applied to every MCP query.
type MCPScopeMode string

const (
	// MCPScopeModeTownAllowlist restricts results to configured town names.
	MCPScopeModeTownAllowlist MCPScopeMode = "town_allowlist"
	// MCPScopeModeAll permits every town in the MCP's fixed query tables.
	MCPScopeModeAll MCPScopeMode = "all"
)

// Config contains immutable application configuration.
type Config struct {
	HTTPAddress string
	SuperAgent  SuperAgentConfig
	Chat        ChatConfig
	MCP         MCPConfig
	PostGIS     PostGISConfig
}

// SuperAgentConfig contains outbound SuperAgent Open API settings.
type SuperAgentConfig struct {
	Enabled                bool
	BaseURL                string
	OpenAPIKey             string
	ConnectTimeout         time.Duration
	RecoveryMaxAttempts    int
	RecoveryInitialBackoff time.Duration
	MaxMessageBytes        int64
	ProbeSubjectID         string
	ProbeTimeout           time.Duration
}

// ChatConfig contains the protected user-facing chat transport and in-memory
// conversation settings. The static credential is a test-stage boundary, not
// final end-user authentication.
type ChatConfig struct {
	Enabled               bool
	PageEnabled           bool
	AuthToken             string
	AllowLegacyShortToken bool
	SubjectID             string
	CompatAppID           string
	AllowedOrigins        []string
	MaxBodyBytes          int64
	RunTimeout            time.Duration
	SessionTTL            time.Duration
	MaxSessions           int
}

// MCPConfig contains inbound SuperAgent MCP settings.
type MCPConfig struct {
	Enabled      bool
	AuthToken    string
	ScopeMode    MCPScopeMode
	AllowedTowns []string
	MaxBodyBytes int64
	ToolTimeout  time.Duration
}

// PostGISConfig contains PostgreSQL/PostGIS connection and query settings.
type PostGISConfig struct {
	Enabled        bool
	DSN            string
	ExpectedSRID   int
	ConnectTimeout time.Duration
	QueryTimeout   time.Duration
	MaxConns       int32
}

// Load reads configuration from the environment, applies safe defaults, and validates it.
func Load() (Config, error) {
	address := strings.TrimSpace(os.Getenv(HTTPAddressEnv))
	if address == "" {
		address = defaultHTTPAddress
	}

	enabled, err := parseBool(SuperAgentEnabledEnv, false)
	if err != nil {
		return Config{}, err
	}
	connectTimeout, err := parseDuration(SuperAgentConnectTimeoutEnv, defaultSuperAgentConnectTimeout)
	if err != nil {
		return Config{}, err
	}
	recoveryMaxAttempts, err := parseInt(SuperAgentRecoveryMaxAttemptsEnv, defaultSuperAgentRecoveryMaxAttempts)
	if err != nil {
		return Config{}, err
	}
	recoveryInitialBackoff, err := parseDuration(SuperAgentRecoveryInitialBackoffEnv, defaultSuperAgentRecoveryBackoff)
	if err != nil {
		return Config{}, err
	}
	maxMessageBytes, err := parseInt64(SuperAgentMaxMessageBytesEnv, defaultSuperAgentMaxMessageBytes)
	if err != nil {
		return Config{}, err
	}
	probeTimeout, err := parseDuration(SuperAgentProbeTimeoutEnv, defaultSuperAgentProbeTimeout)
	if err != nil {
		return Config{}, err
	}

	superAgent := SuperAgentConfig{
		Enabled:                enabled,
		BaseURL:                strings.TrimRight(strings.TrimSpace(os.Getenv(SuperAgentBaseURLEnv)), "/"),
		OpenAPIKey:             strings.TrimSpace(os.Getenv(SuperAgentOpenAPIKeyEnv)),
		ConnectTimeout:         connectTimeout,
		RecoveryMaxAttempts:    recoveryMaxAttempts,
		RecoveryInitialBackoff: recoveryInitialBackoff,
		MaxMessageBytes:        maxMessageBytes,
		ProbeSubjectID:         valueOrDefault(SuperAgentProbeSubjectIDEnv, defaultSuperAgentProbeSubjectID),
		ProbeTimeout:           probeTimeout,
	}
	if err := validateSuperAgent(superAgent); err != nil {
		return Config{}, err
	}

	chat, err := loadChatConfig()
	if err != nil {
		return Config{}, err
	}

	mcp, err := loadMCPConfig()
	if err != nil {
		return Config{}, err
	}
	postGIS, err := loadPostGISConfig()
	if err != nil {
		return Config{}, err
	}
	if err := validateMCPDependencies(mcp, postGIS, superAgent); err != nil {
		return Config{}, err
	}
	if err := validateChatDependencies(chat, superAgent, mcp); err != nil {
		return Config{}, err
	}

	return Config{
		HTTPAddress: address,
		SuperAgent:  superAgent,
		Chat:        chat,
		MCP:         mcp,
		PostGIS:     postGIS,
	}, nil
}

func loadChatConfig() (ChatConfig, error) {
	enabled, err := parseBool(ChatEnabledEnv, false)
	if err != nil {
		return ChatConfig{}, err
	}
	pageEnabled, err := parseBool(ChatPageEnabledEnv, false)
	if err != nil {
		return ChatConfig{}, err
	}
	allowLegacyShortToken, err := parseBool(ChatAllowLegacyShortTokenEnv, false)
	if err != nil {
		return ChatConfig{}, err
	}
	maxBodyBytes, err := parseInt64(ChatMaxBodyBytesEnv, defaultChatMaxBodyBytes)
	if err != nil {
		return ChatConfig{}, err
	}
	runTimeout, err := parseDuration(ChatRunTimeoutEnv, defaultChatRunTimeout)
	if err != nil {
		return ChatConfig{}, err
	}
	sessionTTL, err := parseDuration(ChatSessionTTLEnv, defaultChatSessionTTL)
	if err != nil {
		return ChatConfig{}, err
	}
	maxSessions, err := parseInt64(ChatMaxSessionsEnv, defaultChatMaxSessions)
	if err != nil {
		return ChatConfig{}, err
	}
	allowedOrigins, err := normalizeChatOrigins(parseList(os.Getenv(ChatAllowedOriginsEnv)))
	if err != nil {
		return ChatConfig{}, err
	}

	cfg := ChatConfig{
		Enabled:               enabled,
		PageEnabled:           pageEnabled,
		AuthToken:             os.Getenv(ChatAuthTokenEnv),
		AllowLegacyShortToken: allowLegacyShortToken,
		SubjectID:             valueOrDefault(ChatSubjectIDEnv, defaultChatSubjectID),
		CompatAppID:           strings.TrimSpace(os.Getenv(ChatCompatAppIDEnv)),
		AllowedOrigins:        allowedOrigins,
		MaxBodyBytes:          maxBodyBytes,
		RunTimeout:            runTimeout,
		SessionTTL:            sessionTTL,
		MaxSessions:           int(maxSessions),
	}
	if cfg.MaxBodyBytes <= 0 || cfg.MaxBodyBytes > maximumChatBodyBytes {
		return ChatConfig{}, fmt.Errorf("%s must be between 1 and %d", ChatMaxBodyBytesEnv, maximumChatBodyBytes)
	}
	if cfg.RunTimeout <= 0 || cfg.RunTimeout > maximumChatRunTimeout {
		return ChatConfig{}, fmt.Errorf("%s must be greater than zero and not exceed %s", ChatRunTimeoutEnv, maximumChatRunTimeout)
	}
	if cfg.SessionTTL <= 0 || cfg.SessionTTL > maximumChatSessionTTL {
		return ChatConfig{}, fmt.Errorf("%s must be greater than zero and not exceed %s", ChatSessionTTLEnv, maximumChatSessionTTL)
	}
	if maxSessions <= 0 || maxSessions > maximumChatMaxSessions {
		return ChatConfig{}, fmt.Errorf("%s must be between 1 and %d", ChatMaxSessionsEnv, maximumChatMaxSessions)
	}
	if strings.TrimSpace(cfg.SubjectID) == "" || len(cfg.SubjectID) > 512 || containsControlCharacter(cfg.SubjectID) {
		return ChatConfig{}, fmt.Errorf("%s must be a non-empty value of at most 512 bytes without control characters", ChatSubjectIDEnv)
	}
	if cfg.CompatAppID != "" && !validChatCompatAppID(cfg.CompatAppID) {
		return ChatConfig{}, fmt.Errorf("%s must contain 1 to 128 ASCII letters, digits, underscores, or hyphens", ChatCompatAppIDEnv)
	}
	if cfg.Enabled && !validChatAuthToken(cfg.AuthToken, cfg.AllowLegacyShortToken) {
		if cfg.AllowLegacyShortToken {
			return ChatConfig{}, fmt.Errorf("%s must contain 1 to 4096 printable ASCII characters when %s is true", ChatAuthTokenEnv, ChatAllowLegacyShortTokenEnv)
		}
		return ChatConfig{}, fmt.Errorf("%s must contain 32 to 4096 printable ASCII characters", ChatAuthTokenEnv)
	}
	return cfg, nil
}

func validChatAuthToken(value string, allowLegacyShortToken bool) bool {
	if !validSecretHeaderValue(value) {
		return false
	}
	return allowLegacyShortToken || len(value) >= 32
}

func validChatCompatAppID(value string) bool {
	if value == "" || len(value) > 128 {
		return false
	}
	for _, character := range value {
		if !(character >= 'a' && character <= 'z') &&
			!(character >= 'A' && character <= 'Z') &&
			!(character >= '0' && character <= '9') &&
			character != '_' && character != '-' {
			return false
		}
	}
	return true
}

func normalizeChatOrigins(values []string) ([]string, error) {
	if len(values) > maximumChatAllowedOrigins {
		return nil, fmt.Errorf("%s must contain no more than %d values", ChatAllowedOriginsEnv, maximumChatAllowedOrigins)
	}
	normalized := make([]string, 0, len(values))
	seen := make(map[string]struct{}, len(values))
	for _, value := range values {
		parsed, err := url.Parse(value)
		if err != nil || parsed.Host == "" || (parsed.Scheme != "http" && parsed.Scheme != "https") ||
			parsed.User != nil || parsed.RawQuery != "" || parsed.ForceQuery || parsed.Fragment != "" ||
			(parsed.Path != "" && parsed.Path != "/") || value == "*" {
			return nil, fmt.Errorf("%s must contain only exact HTTP(S) origins", ChatAllowedOriginsEnv)
		}
		origin := parsed.Scheme + "://" + parsed.Host
		if _, exists := seen[origin]; exists {
			continue
		}
		seen[origin] = struct{}{}
		normalized = append(normalized, origin)
	}
	return normalized, nil
}

func loadMCPConfig() (MCPConfig, error) {
	enabled, err := parseBool(MCPEnabledEnv, false)
	if err != nil {
		return MCPConfig{}, err
	}
	scopeMode, err := parseMCPScopeMode(os.Getenv(MCPScopeModeEnv))
	if err != nil {
		return MCPConfig{}, err
	}
	maxBodyBytes, err := parseInt64(MCPMaxBodyBytesEnv, defaultMCPMaxBodyBytes)
	if err != nil {
		return MCPConfig{}, err
	}
	toolTimeout, err := parseDuration(MCPToolTimeoutEnv, defaultMCPToolTimeout)
	if err != nil {
		return MCPConfig{}, err
	}

	cfg := MCPConfig{
		Enabled:      enabled,
		AuthToken:    strings.TrimSpace(os.Getenv(MCPAuthTokenEnv)),
		ScopeMode:    scopeMode,
		AllowedTowns: parseList(os.Getenv(MCPAllowedTownsEnv)),
		MaxBodyBytes: maxBodyBytes,
		ToolTimeout:  toolTimeout,
	}
	if cfg.MaxBodyBytes <= 0 || cfg.MaxBodyBytes > maximumMCPBodyBytes {
		return MCPConfig{}, fmt.Errorf("%s must be between 1 and %d", MCPMaxBodyBytesEnv, maximumMCPBodyBytes)
	}
	if cfg.ToolTimeout <= 0 || cfg.ToolTimeout > maximumMCPToolTimeout {
		return MCPConfig{}, fmt.Errorf("%s must be greater than zero and not exceed %s", MCPToolTimeoutEnv, maximumMCPToolTimeout)
	}
	if !cfg.Enabled {
		return cfg, nil
	}
	if len(cfg.AuthToken) < 32 || !validSecretHeaderValue(cfg.AuthToken) {
		return MCPConfig{}, fmt.Errorf("%s must contain at least 32 printable ASCII characters", MCPAuthTokenEnv)
	}
	switch cfg.ScopeMode {
	case MCPScopeModeAll:
		if len(cfg.AllowedTowns) > 0 {
			return MCPConfig{}, fmt.Errorf("%s must be empty when %s is %s", MCPAllowedTownsEnv, MCPScopeModeEnv, MCPScopeModeAll)
		}
	case MCPScopeModeTownAllowlist:
		if len(cfg.AllowedTowns) == 0 {
			return MCPConfig{}, fmt.Errorf("%s is required when %s is %s", MCPAllowedTownsEnv, MCPScopeModeEnv, MCPScopeModeTownAllowlist)
		}
		if len(cfg.AllowedTowns) > 100 {
			return MCPConfig{}, fmt.Errorf("%s must contain no more than 100 values", MCPAllowedTownsEnv)
		}
		for _, town := range cfg.AllowedTowns {
			if len([]rune(town)) > 100 || containsControlCharacter(town) {
				return MCPConfig{}, fmt.Errorf("%s contains an invalid town value", MCPAllowedTownsEnv)
			}
		}
	}
	return cfg, nil
}

func parseMCPScopeMode(raw string) (MCPScopeMode, error) {
	value := MCPScopeMode(strings.ToLower(strings.TrimSpace(raw)))
	if value == "" {
		return defaultMCPScopeMode, nil
	}
	switch value {
	case MCPScopeModeTownAllowlist, MCPScopeModeAll:
		return value, nil
	default:
		return "", fmt.Errorf("%s must be %q or %q", MCPScopeModeEnv, MCPScopeModeTownAllowlist, MCPScopeModeAll)
	}
}

func containsControlCharacter(value string) bool {
	for _, character := range value {
		if unicode.IsControl(character) {
			return true
		}
	}
	return false
}

func loadPostGISConfig() (PostGISConfig, error) {
	enabled, err := parseBool(PostGISEnabledEnv, false)
	if err != nil {
		return PostGISConfig{}, err
	}
	expectedSRID, err := parseInt(PostGISExpectedSRIDEnv, 0)
	if err != nil {
		return PostGISConfig{}, err
	}
	connectTimeout, err := parseDuration(PostGISConnectTimeoutEnv, defaultPostGISConnectTimeout)
	if err != nil {
		return PostGISConfig{}, err
	}
	queryTimeout, err := parseDuration(PostGISQueryTimeoutEnv, defaultPostGISQueryTimeout)
	if err != nil {
		return PostGISConfig{}, err
	}
	maxConns, err := parseInt64(PostGISMaxConnsEnv, defaultPostGISMaxConns)
	if err != nil {
		return PostGISConfig{}, err
	}

	cfg := PostGISConfig{
		Enabled:        enabled,
		DSN:            strings.TrimSpace(os.Getenv(PostGISDSNEnv)),
		ExpectedSRID:   expectedSRID,
		ConnectTimeout: connectTimeout,
		QueryTimeout:   queryTimeout,
		MaxConns:       int32(maxConns),
	}
	if cfg.ConnectTimeout <= 0 || cfg.ConnectTimeout > maximumPostGISTimeout {
		return PostGISConfig{}, fmt.Errorf("%s must be greater than zero and not exceed %s", PostGISConnectTimeoutEnv, maximumPostGISTimeout)
	}
	if cfg.QueryTimeout <= 0 || cfg.QueryTimeout > maximumPostGISTimeout {
		return PostGISConfig{}, fmt.Errorf("%s must be greater than zero and not exceed %s", PostGISQueryTimeoutEnv, maximumPostGISTimeout)
	}
	if maxConns <= 0 || maxConns > maximumPostGISMaxConns {
		return PostGISConfig{}, fmt.Errorf("%s must be between 1 and %d", PostGISMaxConnsEnv, maximumPostGISMaxConns)
	}
	if cfg.ExpectedSRID < 0 || cfg.ExpectedSRID > 999999 {
		return PostGISConfig{}, fmt.Errorf("%s must be between 0 and 999999", PostGISExpectedSRIDEnv)
	}
	if !cfg.Enabled {
		return cfg, nil
	}
	if cfg.DSN == "" {
		return PostGISConfig{}, fmt.Errorf("%s is required when %s is true", PostGISDSNEnv, PostGISEnabledEnv)
	}
	if !validPostGISDSN(cfg.DSN) {
		return PostGISConfig{}, fmt.Errorf("%s must be an absolute postgresql:// or postgres:// URL", PostGISDSNEnv)
	}
	return cfg, nil
}

func validateMCPDependencies(mcp MCPConfig, postGIS PostGISConfig, superAgent SuperAgentConfig) error {
	if !mcp.Enabled {
		return nil
	}
	if !postGIS.Enabled {
		return fmt.Errorf("%s must be true when %s is true", PostGISEnabledEnv, MCPEnabledEnv)
	}
	if postGIS.ExpectedSRID != requiredMCPSpatialSRID {
		return fmt.Errorf("%s must be explicitly set to %d when %s is true", PostGISExpectedSRIDEnv, requiredMCPSpatialSRID, MCPEnabledEnv)
	}
	if superAgent.OpenAPIKey != "" && mcp.AuthToken == superAgent.OpenAPIKey {
		return fmt.Errorf("%s must not reuse %s", MCPAuthTokenEnv, SuperAgentOpenAPIKeyEnv)
	}
	return nil
}

func validateChatDependencies(chat ChatConfig, superAgent SuperAgentConfig, mcp MCPConfig) error {
	if chat.PageEnabled {
		if !chat.Enabled {
			return fmt.Errorf("%s must be true when %s is true", ChatEnabledEnv, ChatPageEnabledEnv)
		}
		if chat.CompatAppID == "" {
			return fmt.Errorf("%s is required when %s is true", ChatCompatAppIDEnv, ChatPageEnabledEnv)
		}
		if len(chat.AllowedOrigins) == 0 {
			return fmt.Errorf("%s must contain at least one exact HTTP(S) origin when %s is true", ChatAllowedOriginsEnv, ChatPageEnabledEnv)
		}
	}
	if !chat.Enabled {
		return nil
	}
	if !superAgent.Enabled {
		return fmt.Errorf("%s must be true when %s is true", SuperAgentEnabledEnv, ChatEnabledEnv)
	}
	if chat.AuthToken == superAgent.OpenAPIKey {
		return fmt.Errorf("%s must not reuse %s", ChatAuthTokenEnv, SuperAgentOpenAPIKeyEnv)
	}
	if mcp.AuthToken != "" && chat.AuthToken == mcp.AuthToken {
		return fmt.Errorf("%s must not reuse %s", ChatAuthTokenEnv, MCPAuthTokenEnv)
	}
	return nil
}

func validateSuperAgent(cfg SuperAgentConfig) error {
	if cfg.ConnectTimeout <= 0 {
		return fmt.Errorf("%s must be greater than zero", SuperAgentConnectTimeoutEnv)
	}
	if cfg.RecoveryMaxAttempts < 0 {
		return fmt.Errorf("%s must not be negative", SuperAgentRecoveryMaxAttemptsEnv)
	}
	if cfg.RecoveryMaxAttempts > maximumSuperAgentRecoveryAttempts {
		return fmt.Errorf("%s must not exceed %d", SuperAgentRecoveryMaxAttemptsEnv, maximumSuperAgentRecoveryAttempts)
	}
	if cfg.RecoveryInitialBackoff <= 0 {
		return fmt.Errorf("%s must be greater than zero", SuperAgentRecoveryInitialBackoffEnv)
	}
	if cfg.MaxMessageBytes <= 0 {
		return fmt.Errorf("%s must be greater than zero", SuperAgentMaxMessageBytesEnv)
	}
	if cfg.MaxMessageBytes > maximumSuperAgentMessageBytes {
		return fmt.Errorf("%s must not exceed %d", SuperAgentMaxMessageBytesEnv, maximumSuperAgentMessageBytes)
	}
	if cfg.ProbeTimeout <= 0 {
		return fmt.Errorf("%s must be greater than zero", SuperAgentProbeTimeoutEnv)
	}
	if !cfg.Enabled {
		return nil
	}
	if cfg.BaseURL == "" {
		return fmt.Errorf("%s is required when %s is true", SuperAgentBaseURLEnv, SuperAgentEnabledEnv)
	}
	if cfg.OpenAPIKey == "" {
		return fmt.Errorf("%s is required when %s is true", SuperAgentOpenAPIKeyEnv, SuperAgentEnabledEnv)
	}
	if !validSecretHeaderValue(cfg.OpenAPIKey) {
		return fmt.Errorf("%s must be a valid header token", SuperAgentOpenAPIKeyEnv)
	}
	if strings.TrimSpace(cfg.ProbeSubjectID) == "" || len(cfg.ProbeSubjectID) > 512 {
		return fmt.Errorf("%s is required when %s is true", SuperAgentProbeSubjectIDEnv, SuperAgentEnabledEnv)
	}
	parsed, err := url.Parse(cfg.BaseURL)
	if err != nil || parsed.Host == "" || (parsed.Scheme != "http" && parsed.Scheme != "https") {
		return fmt.Errorf("%s must be an absolute HTTP(S) URL", SuperAgentBaseURLEnv)
	}
	if parsed.User != nil || parsed.RawQuery != "" || parsed.Fragment != "" {
		return fmt.Errorf("%s must not include user information, query, or fragment", SuperAgentBaseURLEnv)
	}
	return nil
}

func validSecretHeaderValue(value string) bool {
	if value == "" || len(value) > 4096 {
		return false
	}
	for _, character := range value {
		if character <= 0x20 || character >= 0x7f {
			return false
		}
	}
	return true
}

func validPostGISDSN(value string) bool {
	parsed, err := url.Parse(value)
	if err != nil || parsed.Host == "" {
		return false
	}
	return parsed.Scheme == "postgres" || parsed.Scheme == "postgresql"
}

func parseList(raw string) []string {
	seen := make(map[string]struct{})
	values := make([]string, 0)
	for _, item := range strings.Split(raw, ",") {
		value := strings.TrimSpace(item)
		if value == "" {
			continue
		}
		if _, ok := seen[value]; ok {
			continue
		}
		seen[value] = struct{}{}
		values = append(values, value)
	}
	return values
}

func parseBool(key string, fallback bool) (bool, error) {
	raw := strings.TrimSpace(os.Getenv(key))
	if raw == "" {
		return fallback, nil
	}
	value, err := strconv.ParseBool(raw)
	if err != nil {
		return false, fmt.Errorf("%s must be a boolean", key)
	}
	return value, nil
}

func parseDuration(key string, fallback time.Duration) (time.Duration, error) {
	raw := strings.TrimSpace(os.Getenv(key))
	if raw == "" {
		return fallback, nil
	}
	value, err := time.ParseDuration(raw)
	if err != nil {
		return 0, fmt.Errorf("%s must be a valid duration", key)
	}
	return value, nil
}

func parseInt(key string, fallback int) (int, error) {
	raw := strings.TrimSpace(os.Getenv(key))
	if raw == "" {
		return fallback, nil
	}
	value, err := strconv.Atoi(raw)
	if err != nil {
		return 0, fmt.Errorf("%s must be an integer", key)
	}
	return value, nil
}

func parseInt64(key string, fallback int64) (int64, error) {
	raw := strings.TrimSpace(os.Getenv(key))
	if raw == "" {
		return fallback, nil
	}
	value, err := strconv.ParseInt(raw, 10, 64)
	if err != nil {
		return 0, fmt.Errorf("%s must be an integer", key)
	}
	return value, nil
}

func valueOrDefault(key, fallback string) string {
	value := strings.TrimSpace(os.Getenv(key))
	if value == "" {
		return fallback
	}
	return value
}