// Package kratos is a thin client for the Ory Kratos APIs. honeyDue
// delegates all identity concerns (credentials, sessions, verification,
// recovery, social sign-in) to Kratos; this client validates sessions
// against the public API and deletes identities via the admin API.
package kratos

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// ErrUnauthorized is returned by Whoami when the session is missing, invalid,
// or inactive — the caller should respond 401.
var ErrUnauthorized = errors.New("kratos: session invalid or inactive")

// ErrIdentityExists is returned by CreateIdentity when an identity with the
// same credential identifier (email) already exists — caller should respond 409.
var ErrIdentityExists = errors.New("kratos: identity already exists")

// ErrInvalidCredentials is returned by CreateIdentity when Kratos rejects the
// password against its policy (too short, breached, etc.) — caller responds 400.
type ErrInvalidCredentials struct{ Reason string }

func (e *ErrInvalidCredentials) Error() string { return "kratos: " + e.Reason }

// Client talks to the Ory Kratos public and admin APIs.
type Client struct {
	publicURL string
	adminURL  string
	http      *http.Client
}

// NewClient builds a Kratos client. publicURL is the public-API base used for
// session validation (e.g. http://kratos:4433 in-cluster); adminURL is the
// admin-API base used for identity management (e.g. http://kratos:4434).
// Either may be empty when the corresponding API is unused.
func NewClient(publicURL, adminURL string) *Client {
	return &Client{
		publicURL: strings.TrimRight(publicURL, "/"),
		adminURL:  strings.TrimRight(adminURL, "/"),
		http:      &http.Client{Timeout: 5 * time.Second},
	}
}

// Identity is the subset of a Kratos identity honeyDue consumes. It mirrors
// the identity schema in deploy-k3s/manifests/kratos/configmap.yaml.
type Identity struct {
	ID     string `json:"id"` // UUID — the stable identity identifier
	Traits struct {
		Email string `json:"email"`
		Name  struct {
			First string `json:"first"`
			Last  string `json:"last"`
		} `json:"name"`
	} `json:"traits"`
	VerifiableAddresses []struct {
		Value    string `json:"value"`
		Verified bool   `json:"verified"`
	} `json:"verifiable_addresses"`
}

// Session is a Kratos session as returned by GET /sessions/whoami.
type Session struct {
	ID       string   `json:"id"`
	Active   bool     `json:"active"`
	Identity Identity `json:"identity"`
}

// EmailVerified reports whether any of the identity's email addresses is
// verified — the source of truth for honeyDue's RequireVerified gate.
func (s *Session) EmailVerified() bool {
	for _, a := range s.Identity.VerifiableAddresses {
		if a.Verified {
			return true
		}
	}
	return false
}

// Whoami validates a session against Kratos. Supply the mobile session token
// (sessionToken) OR the browser cookie header (cookie) — whichever is
// non-empty is forwarded to Kratos. Returns ErrUnauthorized for an invalid or
// inactive session.
func (c *Client) Whoami(ctx context.Context, sessionToken, cookie string) (*Session, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.publicURL+"/sessions/whoami", nil)
	if err != nil {
		return nil, err
	}
	if sessionToken != "" {
		req.Header.Set("X-Session-Token", sessionToken)
	}
	if cookie != "" {
		req.Header.Set("Cookie", cookie)
	}

	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("kratos whoami: %w", err)
	}
	defer resp.Body.Close()

	switch {
	case resp.StatusCode == http.StatusUnauthorized, resp.StatusCode == http.StatusForbidden:
		return nil, ErrUnauthorized
	case resp.StatusCode != http.StatusOK:
		return nil, fmt.Errorf("kratos whoami: unexpected status %d", resp.StatusCode)
	}

	var s Session
	if err := json.NewDecoder(resp.Body).Decode(&s); err != nil {
		return nil, fmt.Errorf("kratos whoami: decode: %w", err)
	}
	if !s.Active || s.Identity.ID == "" {
		return nil, ErrUnauthorized
	}
	return &s, nil
}

// CreateIdentity admin-creates a Kratos identity with a password credential and
// an UNVERIFIED email, returning the created identity (with its UUID).
//
// Why admin-create instead of the self-service registration flow: self-service
// registration always auto-emails a verification code to a flow whose id Kratos
// never returns to the client (verified 2026-06-03 — true with and without the
// session after-hook), so the client can never submit the user's code to the
// right flow. Admin creation runs no registration hooks and sends no email, so
// honeyDue drives verification explicitly afterward: the client starts its own
// verification flow (the single code) and the user enters it. The new identity
// is fully usable immediately — the client logs in right after to get a session
// (Kratos permits login for unverified identities; app access is gated on the
// verified flag, not on Kratos login).
//
// password is sent in cleartext over the in-cluster admin API (never exposed
// publicly); Kratos hashes it with the configured bcrypt cost and applies the
// password policy, returning 400 on a weak/breached password and 409 on a
// duplicate email.
func (c *Client) CreateIdentity(ctx context.Context, email, firstName, lastName, password string) (*Identity, error) {
	if c.adminURL == "" {
		return nil, errors.New("kratos: admin URL not configured")
	}
	payload := map[string]any{
		"schema_id": "honeydue",
		"traits": map[string]any{
			"email": email,
			"name":  map[string]any{"first": firstName, "last": lastName},
		},
		"credentials": map[string]any{
			"password": map[string]any{
				"config": map[string]any{"password": password},
			},
		},
	}
	buf, err := json.Marshal(payload)
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.adminURL+"/admin/identities", bytes.NewReader(buf))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("kratos create identity: %w", err)
	}
	defer resp.Body.Close()

	switch resp.StatusCode {
	case http.StatusCreated, http.StatusOK:
		var id Identity
		if err := json.NewDecoder(resp.Body).Decode(&id); err != nil {
			return nil, fmt.Errorf("kratos create identity: decode: %w", err)
		}
		return &id, nil
	case http.StatusConflict:
		return nil, ErrIdentityExists
	case http.StatusBadRequest:
		body, _ := io.ReadAll(resp.Body)
		return nil, &ErrInvalidCredentials{Reason: kratosReason(body)}
	default:
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("kratos create identity: unexpected status %d: %s", resp.StatusCode, string(body))
	}
}

// kratosReason pulls a human-readable reason out of a Kratos error body
// ({"error":{"reason":"...","message":"..."}}), falling back to the raw body.
func kratosReason(body []byte) string {
	var env struct {
		Error struct {
			Reason  string `json:"reason"`
			Message string `json:"message"`
		} `json:"error"`
	}
	if json.Unmarshal(body, &env) == nil {
		if env.Error.Reason != "" {
			return env.Error.Reason
		}
		if env.Error.Message != "" {
			return env.Error.Message
		}
	}
	return strings.TrimSpace(string(body))
}

// DeleteIdentity permanently removes a Kratos identity by its UUID via the
// admin API (DELETE /admin/identities/{id}). A 404 is treated as success —
// the identity is already gone, which is the desired end state, so the call
// is idempotent across retries. Called when a honeyDue account is deleted so
// no orphaned, still-loginable identity is left behind.
func (c *Client) DeleteIdentity(ctx context.Context, identityID string) error {
	if c.adminURL == "" {
		return errors.New("kratos: admin URL not configured")
	}
	if identityID == "" {
		return errors.New("kratos: empty identity id")
	}
	endpoint := c.adminURL + "/admin/identities/" + url.PathEscape(identityID)
	req, err := http.NewRequestWithContext(ctx, http.MethodDelete, endpoint, nil)
	if err != nil {
		return err
	}

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("kratos delete identity: %w", err)
	}
	defer resp.Body.Close()

	switch resp.StatusCode {
	case http.StatusNoContent, http.StatusNotFound:
		return nil
	default:
		return fmt.Errorf("kratos delete identity: unexpected status %d", resp.StatusCode)
	}
}