package majordomo

import (
	"errors"
	"fmt"
	"sort"
	"strings"

	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
)

// ErrInvalidDSN reports a malformed env-DSN value.
var ErrInvalidDSN = errors.New("invalid DSN")

// ErrUnknownProvider reports a spec element whose provider could not be
// resolved through the registry or the LLM_* environment.
var ErrUnknownProvider = errors.New("unknown provider")

// DSN is a parsed provider Data Source Name, as used in LLM_* env vars.
//
// Format (go-llm parity): scheme://[token@]host[/path]
//
//	LLM_M1=foreman://test-token@foreman-m1.example.com
//
// defines provider "m1": a foreman target at https://foreman-m1.example.com
// authenticated with the bearer token "test-token".
type DSN struct {
	// Scheme selects the provider implementation: "foreman", "ollama",
	// "ollama-cloud", "openai", "anthropic", "google"/"gemini", or any
	// custom scheme registered with RegisterScheme.
	Scheme string
	// Token is the provider secret (bearer token or API key); empty = none.
	Token string
	// Host is hostname[:port][/path] with no scheme prefix and no trailing
	// slash.
	Host string
}

// BaseURL returns the https base URL for the DSN host (go-llm parity:
// env-defined providers always speak TLS).
func (d DSN) BaseURL() string { return "https://" + d.Host }

// ParseDSN parses a raw DSN string. The algorithm matches go-llm exactly:
// split on "://", then an optional "@" separates the token from the host;
// trailing slashes on the host are trimmed.
func ParseDSN(raw string) (DSN, error) {
	scheme, rest, found := strings.Cut(raw, "://")
	if !found {
		return DSN{}, fmt.Errorf("%w: missing scheme://: %q", ErrInvalidDSN, raw)
	}

	var token, host string
	if before, after, hasAt := strings.Cut(rest, "@"); hasAt {
		token = before
		host = after
	} else {
		host = rest
	}
	host = strings.TrimRight(host, "/")
	if host == "" {
		return DSN{}, fmt.Errorf("%w: missing host: %q", ErrInvalidDSN, raw)
	}
	return DSN{Scheme: scheme, Token: token, Host: host}, nil
}

// LoadEnv registers a provider for every LLM_<NAME> entry in env. <NAME> is
// lowercased to form the registry name (LLM_M1 → "m1"); the value is a DSN
// whose scheme selects the factory. Entries that fail to parse are recorded
// and their error is returned (joined) — and also surfaces later if the
// name is referenced in Parse — but valid entries always register.
//
// New() calls this with the process environment; tests call it explicitly.
func (r *Registry) LoadEnv(env map[string]string) error {
	// Deterministic order makes error output stable.
	keys := make([]string, 0, len(env))
	for k := range env {
		if strings.HasPrefix(k, "LLM_") && len(k) > len("LLM_") {
			keys = append(keys, k)
		}
	}
	sort.Strings(keys)

	var errs []error
	for _, key := range keys {
		name := strings.ToLower(strings.TrimPrefix(key, "LLM_"))
		p, err := r.providerFromDSN(name, env[key])
		if err != nil {
			err = fmt.Errorf("%s: %w", key, err)
			errs = append(errs, err)
			r.mu.Lock()
			r.envErrs[name] = err
			r.mu.Unlock()
			continue
		}
		r.mu.Lock()
		r.providers[name] = p
		delete(r.envErrs, name)
		r.mu.Unlock()
	}
	return errors.Join(errs...)
}

// providerFromDSN parses a DSN and builds a provider via its scheme factory.
func (r *Registry) providerFromDSN(name, raw string) (llm.Provider, error) {
	dsn, err := ParseDSN(raw)
	if err != nil {
		return nil, err
	}
	r.mu.RLock()
	factory, ok := r.schemes[dsn.Scheme]
	r.mu.RUnlock()
	if !ok {
		return nil, fmt.Errorf("%w: DSN scheme %q is not a registered scheme", ErrUnknownProvider, dsn.Scheme)
	}
	p, err := factory(name, dsn)
	if err != nil {
		return nil, fmt.Errorf("scheme %q: %w", dsn.Scheme, err)
	}
	return p, nil
}