package api

import (
	"context"
	"errors"
	"net/http"

	"git.golem15.com/golem15/sm-seo-plugin/classes"
)

// ApplyBatchInput is the body of POST /_seo/api/v1/batch.
type ApplyBatchInput struct {
	DryRun  bool                  `json:"dry_run,omitempty" jsonschema:"answer the diff and the conflicts without writing anything"`
	Changes []classes.BatchChange `json:"changes" jsonschema:"the changes, applied in order: op set_seo (url, locale, values, force_rule), create_redirect and update_redirect (id, redirect), delete_redirect (id), create_rule and update_rule (id, rule), delete_rule (id)"`
}

// ApplyBatch serves POST /_seo/api/v1/batch (D-12, P-26): the changes run
// in one transaction. With dry_run the answer is every change's diff and
// the conflicts (redirect loops and chains, noindex on a published
// record's address, a canonical pointing to a redirected or noindex
// address) and nothing is written. Without it the batch is applied as a
// whole under one batch id, which history and undo_batch use. A refused
// change refuses the whole batch with 422: redirect_loop with the change
// and the loop's path, or batch_refused with the change's errors.
func ApplyBatch(service func() *classes.Service) http.HandlerFunc {
	return manage(service, func(ctx context.Context, svc *classes.Service, r *http.Request) (int, any, error) {
		var in ApplyBatchInput
		if err := decode(r, 4*maxBody, &in); err != nil {
			return 0, nil, err
		}
		res, err := svc.RunBatch(ctx, in.Changes, classes.BatchOptions{DryRun: in.DryRun})
		var refused *classes.BatchRefusedError
		if errors.As(err, &refused) {
			return 0, nil, &apiError{Status: http.StatusUnprocessableEntity, Body: BatchRefusal(refused.Result)}
		}
		if err != nil {
			return 0, nil, err
		}
		return http.StatusOK, res, nil
	})
}

// BatchRefusal is the 422 answer of a refused batch: the first refused
// change, its error, path or field errors, and every change's outcome.
func BatchRefusal(res classes.BatchResult) map[string]any {
	item := res.Refused()
	out := map[string]any{"error": "batch_refused", "changes": res.Changes}
	if item == nil {
		return out
	}
	out["change"] = item.Index
	out["message"] = item.Message
	if item.Error == classes.ConflictLoop {
		out["error"] = "redirect_loop"
		out["path"] = item.Path
	}
	if len(item.Errors) > 0 {
		out["errors"] = item.Errors
	}
	return out
}