package apify

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

const (
	apiBase     = "https://api.apify.com/v2"
	pollEvery   = 3 * time.Second
	pollTimeout = 5 * time.Minute
)

// Client is a thin wrapper around the Apify run-and-fetch lifecycle.
type Client struct {
	APIKey string
	HTTP   *http.Client
}

func New(apiKey string) *Client {
	return &Client{
		APIKey: apiKey,
		HTTP:   &http.Client{Timeout: 30 * time.Second},
	}
}

type runResponse struct {
	Data struct {
		ID              string `json:"id"`
		Status          string `json:"status"`
		DefaultDatasetID string `json:"defaultDatasetId"`
	} `json:"data"`
}

// Run starts an actor run, waits for SUCCEEDED, and returns dataset items as raw JSON.
func (c *Client) Run(ctx context.Context, actorID string, input any) ([]json.RawMessage, error) {
	if c.APIKey == "" {
		return nil, errors.New("apify api_key not configured")
	}
	if actorID == "" {
		return nil, errors.New("apify actor id is empty")
	}

	body, err := json.Marshal(input)
	if err != nil {
		return nil, err
	}

	// Apify URLs use "~" to separate username and actor name, never "/".
	// Accept either form in config and normalize before path-escaping.
	urlActorID := strings.ReplaceAll(actorID, "/", "~")
	startURL := fmt.Sprintf("%s/acts/%s/runs?token=%s", apiBase, url.PathEscape(urlActorID), url.QueryEscape(c.APIKey))
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, startURL, bytes.NewReader(body))
	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("start run: %w", err)
	}
	var runResp runResponse
	if err := decodeJSON(resp, &runResp); err != nil {
		return nil, fmt.Errorf("start run: %w", err)
	}
	if runResp.Data.ID == "" {
		return nil, errors.New("start run: missing run id")
	}

	deadline := time.Now().Add(pollTimeout)
	pollCtx, cancel := context.WithDeadline(ctx, deadline)
	defer cancel()

	status, datasetID, err := c.waitForRun(pollCtx, runResp.Data.ID)
	if err != nil {
		return nil, err
	}
	if status != "SUCCEEDED" {
		return nil, fmt.Errorf("apify run terminated with status %s", status)
	}

	return c.fetchDataset(ctx, datasetID)
}

func (c *Client) waitForRun(ctx context.Context, runID string) (string, string, error) {
	pollURL := fmt.Sprintf("%s/actor-runs/%s?token=%s", apiBase, url.PathEscape(runID), url.QueryEscape(c.APIKey))
	for {
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, pollURL, nil)
		if err != nil {
			return "", "", err
		}
		resp, err := c.HTTP.Do(req)
		if err != nil {
			return "", "", fmt.Errorf("poll run: %w", err)
		}
		var r runResponse
		if err := decodeJSON(resp, &r); err != nil {
			return "", "", fmt.Errorf("poll run: %w", err)
		}
		switch r.Data.Status {
		case "SUCCEEDED", "FAILED", "ABORTED", "TIMED-OUT":
			return r.Data.Status, r.Data.DefaultDatasetID, nil
		}
		select {
		case <-ctx.Done():
			return "", "", ctx.Err()
		case <-time.After(pollEvery):
		}
	}
}

func (c *Client) fetchDataset(ctx context.Context, datasetID string) ([]json.RawMessage, error) {
	if datasetID == "" {
		return nil, errors.New("missing dataset id")
	}
	dsURL := fmt.Sprintf("%s/datasets/%s/items?clean=true&format=json&token=%s", apiBase, url.PathEscape(datasetID), url.QueryEscape(c.APIKey))
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, dsURL, nil)
	if err != nil {
		return nil, err
	}
	resp, err := c.HTTP.Do(req)
	if err != nil {
		return nil, fmt.Errorf("fetch dataset: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		b, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
		return nil, fmt.Errorf("dataset returned %d: %s", resp.StatusCode, string(b))
	}
	var items []json.RawMessage
	if err := json.NewDecoder(resp.Body).Decode(&items); err != nil {
		return nil, fmt.Errorf("decode dataset: %w", err)
	}
	return items, nil
}

func decodeJSON(resp *http.Response, dst any) error {
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		b, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
		return fmt.Errorf("http %d: %s", resp.StatusCode, string(b))
	}
	return json.NewDecoder(resp.Body).Decode(dst)
}