// Package chatto implements a minimal ConnectRPC (Connect protocol, JSON
// codec) client for Chatto servers (tested against 0.5.0-beta.27+).
//
// Why hand-built: the Chatto server repository (github.com/chattocorp/chatto) keeps its
// generated protobuf code and Connect handlers under internal/ — they cannot
// be imported from outside the module. But the server exposes the same API as
// plain Connect JSON over HTTP:
//
//	POST {base}/api/connect/chatto.api.v1.<Service>/<Method>
//	Body: JSON of the request message (proto3 JSON field names)
//	Auth: Authorization: Bearer <token>
//
// See proto/chatto/api/v1/*.proto in the Chatto repository for the message
// schemas; only the subset needed by cheapo is modelled here.
package chatto

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

// Client talks to a Chatto server via the Connect JSON protocol.
type Client struct {
	BaseURL string // e.g. https://chat.example.com
	Token   string // bearer token
	HTTP    *http.Client
}

// NewClient returns a client with a 30 s HTTP timeout.
func NewClient(baseURL, token string) *Client {
	return &Client{
		BaseURL: strings.TrimRight(baseURL, "/"),
		Token:   token,
		HTTP:    &http.Client{Timeout: 30 * time.Second},
	}
}

// connectError models the Connect error envelope
// ({"code": "...", "message": "..."} with HTTP != 200).
type connectError struct {
	Code    string `json:"code"`
	Message string `json:"message"`
}

func (e *connectError) Error() string {
	if e.Message == "" {
		return "chatto: connect error " + e.Code
	}
	return fmt.Sprintf("chatto: %s: %s", e.Code, e.Message)
}

// call performs one Connect unary call with JSON codec.
func call[Req any, Resp any](ctx context.Context, c *Client, service, method string, req *Req) (*Resp, error) {
	url := fmt.Sprintf("%s/api/connect/chatto.api.v1.%s/%s", c.BaseURL, service, method)

	body, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("chatto: encode request: %w", err)
	}
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("chatto: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("Connect-Protocol-Version", "1")
	if c.Token != "" {
		httpReq.Header.Set("Authorization", "Bearer "+c.Token)
	}

	resp, err := c.HTTP.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("chatto: request failed: %w", err)
	}
	defer resp.Body.Close()

	raw, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("chatto: read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		var ce connectError
		if json.Unmarshal(raw, &ce) == nil && ce.Code != "" {
			return nil, &ce
		}
		// Some error paths return HTML (e.g. SPA shell on wrong path).
		snippet := string(raw)
		if len(snippet) > 120 {
			snippet = snippet[:120]
		}
		return nil, fmt.Errorf("chatto: HTTP %s: %s", resp.Status, snippet)
	}

	var out Resp
	if err := json.Unmarshal(raw, &out); err != nil {
		return nil, fmt.Errorf("chatto: decode response: %w", err)
	}
	return &out, nil
}

// --- RoomDirectoryService ---

type Room struct {
	ID          string `json:"id"`
	Kind        string `json:"kind"`
	Name        string `json:"name"`
	Description string `json:"description,omitempty"`
	Archived    bool   `json:"archived,omitempty"`
	GroupID     string `json:"group_id,omitempty"`
	Universal   bool   `json:"universal,omitempty"`
}

type listRoomsRequest struct {
	Page *pageRequest `json:"page,omitempty"`
}

type pageRequest struct {
	PageSize int32 `json:"pageSize,omitempty"`
}

type listRoomsResponse struct {
	Rooms []Room `json:"rooms"`
	Page  struct {
		TotalCount int64 `json:"total_count"`
		HasMore    bool  `json:"has_more"`
	} `json:"page"`
}

// ListRooms returns rooms visible to the token's user (single page, up to 100).
func (c *Client) ListRooms(ctx context.Context) ([]Room, error) {
	resp, err := call[struct{}, listRoomsResponse](ctx, c,
		"RoomDirectoryService", "ListRooms", &struct{}{})
	if err != nil {
		return nil, err
	}
	return resp.Rooms, nil
}

// --- MessageService ---

type Message struct {
	EventID      string `json:"event_id"`
	RoomID       string `json:"room_id"`
	ThreadRoot   string `json:"thread_root_event_id,omitempty"`
	AuthorUserID string `json:"author_user_id,omitempty"`
	Body         string `json:"body,omitempty"`
	CreatedAt    string `json:"created_at,omitempty"`
}

type createMessageRequest struct {
	RoomID            string `json:"room_id"`
	Body              string `json:"body"`
	ThreadRootEventID string `json:"thread_root_event_id,omitempty"`
	InReplyTo         string `json:"in_reply_to,omitempty"`
	AlsoSendToChannel bool   `json:"also_send_to_channel,omitempty"`
}

type createMessageResponse struct {
	Message Message `json:"message"`
}

// CreateMessage posts a message to a room (or thread reply when
// threadRootEventID is set).
func (c *Client) CreateMessage(ctx context.Context, roomID, body string, threadRootEventID string) (*Message, error) {
	req := &createMessageRequest{RoomID: roomID, Body: body}
	if threadRootEventID != "" {
		req.ThreadRootEventID = threadRootEventID
	}
	resp, err := call[createMessageRequest, createMessageResponse](ctx, c,
		"MessageService", "CreateMessage", req)
	if err != nil {
		return nil, err
	}
	return &resp.Message, nil
}

type getMessageRequest struct {
	RoomID  string `json:"room_id"`
	EventID string `json:"event_id"`
}

type getMessageResponse struct {
	Message Message `json:"message"`
}

// GetMessage fetches a single message.
func (c *Client) GetMessage(ctx context.Context, roomID, eventID string) (*Message, error) {
	resp, err := call[getMessageRequest, getMessageResponse](ctx, c,
		"MessageService", "GetMessage", &getMessageRequest{RoomID: roomID, EventID: eventID})
	if err != nil {
		return nil, err
	}
	return &resp.Message, nil
}