// Package matrix wraps mautrix-go for agent use.
package matrix

import (
	"context"
	"crypto/sha256"
	"fmt"
	"io"
	"os"
	"path/filepath"

	"maunium.net/go/mautrix"
	"maunium.net/go/mautrix/crypto/cryptohelper"
	"maunium.net/go/mautrix/event"
	"maunium.net/go/mautrix/id"

	"github.com/enmanuel/agents/internal/config"
)

// Client wraps a mautrix client with agent-relevant helpers.
type Client struct {
	raw *mautrix.Client
	cfg config.MatrixCfg
}

// New creates and authenticates a Matrix client from config.
// The access token is read from the env var specified in cfg.AccessTokenEnv.
func New(cfg config.MatrixCfg) (*Client, error) {
	token := os.Getenv(cfg.AccessTokenEnv)
	if token == "" {
		return nil, fmt.Errorf("env var %s is not set", cfg.AccessTokenEnv)
	}

	raw, err := mautrix.NewClient(cfg.Homeserver, id.UserID(cfg.UserID), token)
	if err != nil {
		return nil, fmt.Errorf("create matrix client: %w", err)
	}

	if cfg.DeviceID != "" {
		raw.DeviceID = id.DeviceID(cfg.DeviceID)
	}

	return &Client{raw: raw, cfg: cfg}, nil
}

// InitCrypto sets up end-to-end encryption using the mautrix cryptohelper.
// storePath is the SQLite file path for crypto material (e.g. "./data/crypto/crypto.db").
// agentID is used to namespace the crypto state so multiple agents can share a database.
// Returns an io.Closer that must be called on agent shutdown to flush the crypto store.
func (c *Client) InitCrypto(ctx context.Context, storePath, agentID string) (io.Closer, error) {
	// Resolve the actual device ID from the server — the value in config may differ
	// from what the registration process assigned.
	whoami, err := c.raw.Whoami(ctx)
	if err != nil {
		return nil, fmt.Errorf("whoami for crypto init: %w", err)
	}
	c.raw.DeviceID = whoami.DeviceID

	// Derive a stable pickle key from the access token.
	// If the token changes (bot re-registered), delete the crypto store to reset.
	sum := sha256.Sum256([]byte(c.raw.AccessToken))
	pickleKey := sum[:]

	if err := os.MkdirAll(filepath.Dir(storePath), 0700); err != nil {
		return nil, fmt.Errorf("create crypto store dir: %w", err)
	}

	helper, err := cryptohelper.NewCryptoHelper(c.raw, pickleKey, storePath)
	if err != nil {
		return nil, fmt.Errorf("create crypto helper: %w", err)
	}
	helper.DBAccountID = agentID

	if err := helper.Init(ctx); err != nil {
		return nil, fmt.Errorf("init e2ee: %w", err)
	}

	c.raw.Crypto = helper
	return helper, nil
}

// SendText sends a plain-text message to a room.
// If the room has E2EE enabled and crypto is initialized, the message is encrypted automatically.
func (c *Client) SendText(ctx context.Context, roomID, text string) error {
	_, err := c.raw.SendText(ctx, id.RoomID(roomID), text)
	return err
}

// SendMarkdown sends a formatted (Markdown) message to a room.
func (c *Client) SendMarkdown(ctx context.Context, roomID, markdown string) error {
	content := event.MessageEventContent{
		MsgType:       event.MsgText,
		Body:          markdown,
		Format:        event.FormatHTML,
		FormattedBody: markdown, // mautrix can render markdown -> HTML if needed
	}
	_, err := c.raw.SendMessageEvent(ctx, id.RoomID(roomID), event.EventMessage, content)
	return err
}

// SendReaction sends a reaction to an event.
func (c *Client) SendReaction(ctx context.Context, roomID, eventID, reaction string) error {
	_, err := c.raw.SendReaction(ctx, id.RoomID(roomID), id.EventID(eventID), reaction)
	return err
}

// SendTyping sets the typing indicator in a room.
func (c *Client) SendTyping(ctx context.Context, roomID string, typing bool) error {
	_, err := c.raw.UserTyping(ctx, id.RoomID(roomID), typing, 5000)
	return err
}

// Raw returns the underlying mautrix.Client for advanced use.
func (c *Client) Raw() *mautrix.Client {
	return c.raw
}