package config

import (
	"encoding/json"
	"os"
	"strings"
)

const defaultEnvPrefix = "GO_OMNI_"

// ServerEnvAliases returns the documented short names for Config fields.
// field is the JSON path of Config in a project (usually "server"), or ""
// for Config itself. Canonical names win over aliases. Both use the same
// EnvOptions.Empty/Lookup and typed parser; collections use JSON syntax.
func ServerEnvAliases(prefix, field string) map[string][]string {
	root := prefix
	if field != "" {
		for _, part := range strings.Split(field, ".") {
			root += envName(part) + "_"
		}
	}
	names := map[string]string{
		"ADDRESS": "HTTP_ADDR", "TRANSPORT": "TRANSPORT", "TLS_CERT_FILE": "TLS_CERT_FILE", "TLS_KEY_FILE": "TLS_KEY_FILE",
		"REQUEST_ID_HEADER": "REQUEST_ID_HEADER", "ENABLE_LOGGER": "ENABLE_LOGGER", "SLOW_REQUEST_THRESHOLD": "SLOW_REQUEST_THRESHOLD",
		"TRUSTED_PROXIES": "TRUSTED_PROXIES", "SHUTDOWN_TIMEOUT": "SHUTDOWN_TIMEOUT",
		"LOG_LEVEL": "LOG_LEVEL", "LOG_FORMAT": "LOG_FORMAT", "LOG_OUTPUT": "LOG_OUTPUT", "LOG_FILE": "LOG_FILE", "LOG_SERVICE": "SERVICE", "LOG_ENVIRONMENT": "ENVIRONMENT", "LOG_ADD_SOURCE": "LOG_ADD_SOURCE",
		"HTTP_READ_HEADER_TIMEOUT": "HTTP_READ_HEADER_TIMEOUT", "HTTP_READ_TIMEOUT": "HTTP_READ_TIMEOUT", "HTTP_WRITE_TIMEOUT": "HTTP_WRITE_TIMEOUT", "HTTP_IDLE_TIMEOUT": "HTTP_IDLE_TIMEOUT", "HTTP_MAX_HEADER_BYTES": "HTTP_MAX_HEADER_BYTES",
		"LIFECYCLE_STOP_TIMEOUT": "LIFECYCLE_STOP_TIMEOUT", "LIFECYCLE_DRAIN_TIMEOUT": "LIFECYCLE_DRAIN_TIMEOUT", "LIFECYCLE_CANCEL_TIMEOUT": "LIFECYCLE_CANCEL_TIMEOUT",
	}
	for _, endpoint := range []string{"LIVENESS", "READINESS", "OPENAPI"} {
		for _, part := range []string{"ENABLED", "PATH", "RESPONSE_MODE"} {
			if endpoint == "OPENAPI" && part == "RESPONSE_MODE" {
				continue
			}
			name := "ENDPOINTS_" + endpoint + "_" + part
			names[name] = name
		}
	}
	aliases := map[string][]string{}
	for key, alias := range names {
		if root+key != prefix+alias {
			aliases[root+key] = []string{prefix + alias}
		}
	}
	return aliases
}

// LoadFromEnv loads defaults using the legacy short-name conventions.
func LoadFromEnv(prefix string) (Config, error) { return ApplyEnv(Default(), prefix) }

// ApplyEnv retains legacy whitespace trimming, ignored empty variables and
// comma-separated TRUSTED_PROXIES. New projects should use OverlayEnv with
// ServerEnvAliases for one explicit empty-value policy across the whole config.
func ApplyEnv(defaults Config, prefix string) (Config, error) {
	prefix = strings.TrimSpace(prefix)
	if prefix == "" {
		prefix = defaultEnvPrefix
	}
	lookup := func(key string) (string, bool) {
		raw, ok := os.LookupEnv(key)
		raw = strings.TrimSpace(raw)
		if ok && raw != "" && key == prefix+"TRUSTED_PROXIES" && !strings.HasPrefix(raw, "[") {
			values := strings.Split(raw, ",")
			for i := range values {
				values[i] = strings.TrimSpace(values[i])
			}
			data, _ := json.Marshal(values)
			raw = string(data)
		}
		return raw, ok
	}
	defaults.Errors = defaults.Errors.Clone()
	defaults.TrustedProxies = append([]string(nil), defaults.TrustedProxies...)
	defaults.Log.RedactKeys = append([]string(nil), defaults.Log.RedactKeys...)
	cfg, err := OverlayEnv(defaults, EnvOptions{Prefix: prefix, Empty: "ignore", Lookup: lookup, Aliases: ServerEnvAliases(prefix, "")})
	if err != nil {
		return Config{}, err
	}
	if err = cfg.Validate(); err != nil {
		return Config{}, err
	}
	return cfg, nil
}