package cli

// Per-server credentials store (TASK-1228 / IDEA-1226).
//
// `~/.pad/credentials.json` previously held a single login blob:
//
//   {"server_url": "...", "token": "padsess_...", "user_id": "...", ...}
//
// That works for one Pad instance per developer machine, but breaks the
// real workflow of one developer on multiple instances (apm/ → cloud,
// target/ → local, testing/ → staging). Switching among them with
// `pad init --url <other>` would clobber the single entry, so going back
// to a previously-authed server meant logging in again.
//
// v2 keys credentials by canonical server URL:
//
//   {
//     "version": 2,
//     "credentials": {
//       "https://app.getpad.dev":      {"token": "...", "user_id": "...", ...},
//       "http://127.0.0.1:7777":       {"token": "...", "user_id": "...", ...},
//       "https://pad-staging:7777":    {"token": "...", "user_id": "...", ...}
//     }
//   }
//
// Reads transparently migrate v1 → v2 in memory; the next Save writes v2.
// We deliberately do NOT save-on-read so reads stay side-effect free —
// the migration becomes durable on the first login/logout/setup.
//
// Single-server users see no behavior change: one entry, same shape per
// entry, identical UX.
//
// No top-level `default` field. The configured server URL
// (cfg.BaseURL() from ~/.pad/config.toml or --url) is always the
// authoritative answer for "which server am I targeting" — a separate
// `default` would create a second source of truth and the split-brain
// bugs that follow. The v2 schema can be extended later if a use case
// shows up; the current map shape is forward compatible.

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

// credentialsVersion is what new saves write. Bump and add a migration
// branch in LoadStore when the on-disk shape changes.
const credentialsVersion = 2

// Credentials is the per-server login blob. The `server_url` JSON tag is
// kept (with omitempty) so v1 files still parse during the migration
// path; in v2 the URL is the map key and the field is redundant — Set
// mirrors the key into the field so consumers reading the value alone
// still see a consistent ServerURL.
type Credentials struct {
	ServerURL string `json:"server_url,omitempty"`
	Token     string `json:"token"`
	UserID    string `json:"user_id"`
	Email     string `json:"email"`
	Name      string `json:"name"`
}

// CredentialStore is the on-disk shape of `~/.pad/credentials.json` (v2).
// Keyed by canonical server URL (trailing slash + surrounding whitespace
// stripped — see normalizeServerURL).
type CredentialStore struct {
	Version     int                     `json:"version"`
	Credentials map[string]*Credentials `json:"credentials"`
}

// CredentialsPath returns ~/.pad/credentials.json.
func CredentialsPath() (string, error) {
	homeDir, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("get home directory: %w", err)
	}
	return filepath.Join(homeDir, ".pad", "credentials.json"), nil
}

// credentialsPath is retained for internal call sites.
func credentialsPath() (string, error) {
	return CredentialsPath()
}

// LoadStore reads the credentials file and returns a usable
// CredentialStore. Returns an empty (but non-nil) store if the file
// doesn't exist — that's not an error, just "nothing logged in
// anywhere." Migrates v1 single-blob format to v2 in memory; v1 files
// stay v1 on disk until the first Save (which always writes v2).
//
// LoadStore is the only intended way to read credentials. Internal
// callers that need a single server's entry should call
// LoadStore().Get(url).
func LoadStore() (*CredentialStore, error) {
	path, err := credentialsPath()
	if err != nil {
		return nil, err
	}

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

	if len(strings.TrimSpace(string(data))) == 0 {
		return newEmptyStore(), nil
	}

	// Detect format. v1 has a top-level `token` string; v2 has a
	// top-level `credentials` object. Probe with a generic map so a
	// garbage file fails loudly here rather than silently parsing as
	// "empty v2."
	var probe map[string]json.RawMessage
	if err := json.Unmarshal(data, &probe); err != nil {
		return nil, fmt.Errorf("parse credentials: %w", err)
	}
	if _, hasToken := probe["token"]; hasToken {
		return migrateV1(data)
	}
	return parseV2(data)
}

// migrateV1 reads a v1 single-blob file and returns an in-memory v2 store
// keyed by the legacy ServerURL. A v1 file with an empty server_url is
// treated as "no usable credentials" (returns an empty store) — that's
// the only safe interpretation, since we have no key to file the entry
// under. The on-disk file is unchanged; callers triggering Save (login,
// logout, setup) will write v2.
func migrateV1(data []byte) (*CredentialStore, error) {
	var legacy Credentials
	if err := json.Unmarshal(data, &legacy); err != nil {
		return nil, fmt.Errorf("parse v1 credentials: %w", err)
	}
	store := newEmptyStore()
	if normalizeServerURL(legacy.ServerURL) != "" && legacy.Token != "" {
		store.Set(legacy.ServerURL, &legacy)
	}
	return store, nil
}

// parseV2 unmarshals a v2 file. Tolerates a missing or zero version
// field and a nil credentials map by normalizing both — anything else
// (malformed JSON, wrong types) surfaces as an error.
func parseV2(data []byte) (*CredentialStore, error) {
	var store CredentialStore
	if err := json.Unmarshal(data, &store); err != nil {
		return nil, fmt.Errorf("parse v2 credentials: %w", err)
	}
	if store.Credentials == nil {
		store.Credentials = map[string]*Credentials{}
	}
	if store.Version == 0 {
		store.Version = credentialsVersion
	}
	return &store, nil
}

func newEmptyStore() *CredentialStore {
	return &CredentialStore{
		Version:     credentialsVersion,
		Credentials: map[string]*Credentials{},
	}
}

// Get returns the credential for the given server URL, or nil if none
// exists. URL is canonicalized (trailing slash + whitespace stripped)
// before lookup. Nil-receiver safe — callers can write
// `store.Get(url)` without a prior nil check on store.
func (s *CredentialStore) Get(serverURL string) *Credentials {
	if s == nil || s.Credentials == nil {
		return nil
	}
	return s.Credentials[normalizeServerURL(serverURL)]
}

// Set adds or replaces the credential for the given server URL. The
// canonical URL is mirrored into the value's ServerURL field so a
// caller reading the credential standalone still sees a consistent
// URL. Passing a nil credential is a no-op (use Delete to remove).
func (s *CredentialStore) Set(serverURL string, c *Credentials) {
	if c == nil {
		return
	}
	if s.Credentials == nil {
		s.Credentials = map[string]*Credentials{}
	}
	key := normalizeServerURL(serverURL)
	c.ServerURL = key
	s.Credentials[key] = c
}

// Delete removes the credential for the given server URL. No-op if the
// entry isn't present, or if the receiver is nil.
func (s *CredentialStore) Delete(serverURL string) {
	if s == nil || s.Credentials == nil {
		return
	}
	delete(s.Credentials, normalizeServerURL(serverURL))
}

// Save writes the store to disk in v2 format with mode 0600. Always
// writes the current version constant — even if the store was loaded
// from v1, this is the migration moment.
func (s *CredentialStore) Save() error {
	path, err := credentialsPath()
	if err != nil {
		return err
	}

	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
		return fmt.Errorf("create credentials directory: %w", err)
	}

	s.Version = credentialsVersion
	if s.Credentials == nil {
		s.Credentials = map[string]*Credentials{}
	}

	data, err := json.MarshalIndent(s, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal credentials: %w", err)
	}

	if err := os.WriteFile(path, data, 0600); err != nil {
		return fmt.Errorf("write credentials: %w", err)
	}
	return nil
}

// WipeCredentialsFile removes ~/.pad/credentials.json entirely. Distinct
// from CredentialStore.Delete (which removes a single server's entry)
// — used by tests and any future "pad auth wipe" that wants a clean
// slate. Silently succeeds if the file is already absent.
func WipeCredentialsFile() error {
	path, err := credentialsPath()
	if err != nil {
		return err
	}
	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("delete credentials: %w", err)
	}
	return nil
}

// normalizeServerURL canonicalizes a server URL for use as a credential
// key. Trailing slash and surrounding whitespace are stripped; nothing
// else is touched (no scheme normalization, no port-canonicalization
// — those are deliberate, since differently-spelled URLs may legitimately
// reach different servers). Mirrors normalizeURL in cmd/pad/server_info.go
// so the two stay consistent.
func normalizeServerURL(u string) string {
	return strings.TrimRight(strings.TrimSpace(u), "/")
}