package fetcher

import (
	"context"
	"errors"
	"log/slog"
	"time"

	"git.avsdev.uk/Go/job-search/internal/config"
	"git.avsdev.uk/Go/job-search/internal/findatender"
	"git.avsdev.uk/Go/job-search/internal/types"
	"git.avsdev.uk/Go/job-search/internal/util"
)

// findATenderSource is the Source of the opportunities Find a Tender's
// converter makes, and so of the ones the Find a Tender source fetches.
const findATenderSource = "FindATender"

// runFindATender polls Find a Tender every configured interval until ctx
// is cancelled, passing what each run fetches to save, even when the run
// fails partway. A long window is backfilled first (see backfill).
func runFindATender(
	ctx context.Context,
	logger *slog.Logger,
	conf *config.JSCSourceFindATender,
	save saveFunc,
	since time.Time,
) error {
	if conf.APIRoot == "" {
		return errors.New("fetcher: sources.find_a_tender.api_root is not set")
	}

	fetch := func(
		ctx context.Context, since, until time.Time,
	) ([]*types.Opportunity, error) {
		return fetchFindATender(ctx, logger, conf, since, until)
	}

	since = backfill(
		ctx,
		logger,
		findATenderSource,
		conf.Interval,
		fetch,
		save,
		since,
	)

	worker := util.Worker{
		Logger:   tagged(logger),
		Name:     findATenderSource,
		Interval: conf.Interval,
		Task: func(ctx context.Context, since time.Time) error {
			opportunities, err := fetch(ctx, since, time.Time{})
			return saveFetched(ctx, logger, save, opportunities, err)
		},
	}
	return worker.Run(ctx, since)
}

// fetchFindATender fetches everything updated from since up to until (zero:
// no bound) from Find a Tender. If it fails partway, what it fetched before
// the error is returned along with it. Finding nothing returns
// ErrNoNewReleases, so the worker still moves its checkpoint on.
func fetchFindATender(
	ctx context.Context,
	logger *slog.Logger,
	conf *config.JSCSourceFindATender,
	since, until time.Time,
) ([]*types.Opportunity, error) {
	opportunities, err := util.AwaitTask(
		ctx,
		func() ([]*types.Opportunity, error) {
			findATender := findatender.New(
				conf.APIRoot, findatender.WithLogger(logger),
			)
			defer findATender.Shutdown()
			return findATender.With(ctx).FetchAll(findatender.RequestOptions{
				Since:            since,
				Until:            until,
				RateLimitRetries: conf.RateLimitRetries,
			})
		},
	)
	if errors.Is(err, findatender.ErrNoReleases) {
		return nil, ErrNoNewReleases
	}

	tagged(logger).Info(
		"fetched opportunities",
		"source", findATenderSource,
		"count", len(opportunities),
	)

	return opportunities, err
}