// Package lulu is a client library for the Lulu book printing API.
package lulu

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

	"golang.org/x/oauth2/clientcredentials"
)

const (
	sandbox    = "https://api.sandbox.lulu.com/"
	production = "https://api.lulu.com/"

	productionKeyPage = "https://developers.lulu.com/user-profile/api-keys"
	sandboxKeyPage    = "https://developers.sandbox.lulu.com/user-profile/api-keys"

	PollPeriod = time.Second

	tokenPath            = "/auth/realms/glasstree/protocol/openid-connect/token"
	validateInteriorPath = "/validate-interior"
	coverDimensionsPath  = "/cover-dimensions"
	validateCoverPath    = "/validate-cover"
	printJobCostPath     = "/print-job-cost-calculations"
	printJobsPath        = "/print-jobs"
)

// A Client connects to the Lulu API server.
type Client interface {
	// StartInteriorValidation starts a server-side validation job for the
	// interior file located at srcUrl using manufacturing settings given
	// by mfg. It returns the ID of the job. Use
	// [Client.GetInteriorValidation] to poll the status of the job.
	//
	// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Interior_create
	StartInteriorValidation(srcUrl string, mfg PkgId) (uint, error)

	// StartInteriorValidationBasic is like
	// [Client.StartInteriorValidation] but without the optional
	// pod_package_id.
	//
	// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Interior_create
	StartInteriorValidationBasic(srcUrl string) (uint, error)

	// GetInteriorValidation retrieves information about an interior file
	// validation job that was started by ValidateInterior().
	//
	// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Interior_read
	GetInteriorValidation(id uint) (InteriorValidation, error)

	// CoverDimensions calculates the required dimensions of the cover for
	// a book with the given manufacturing settings and number of pages.
	// The returned dimensions are given in the specified units of
	// measurement.
	//
	// https://api.lulu.com/docs/#tag/Files-validation/operation/Cover-Dimensions_create
	CoverDimensions(mfg PkgId, npages uint, unit Unit) (CoverDimensions, error)

	// StartCoverValidation starts a server-side validation job for the
	// cover file located at srcUrl, returning the job ID. mfg is the
	// manufacturing settings of the book, and npages is the number of
	// interior pages. Use [Client.GetCoverValidation] to poll the status
	// of the job.
	//
	// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Cover_create
	StartCoverValidation(srcUrl string, mfg PkgId, npages uint) (uint, error)

	// GetCoverValidiation retrieves information about a cover file
	// validation job that was started by ValidateCover().
	//
	// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Cover_read
	GetCoverValidation(id uint) (CoverValidation, error)

	// Cost calculates the cost of a hypothetical print order without
	// actually creating a print job.
	//
	// https://api.lulu.com/docs/#tag/Print-Job-Cost-Calculations/operation/Print-Job-cost-calculations_create
	Cost(items []CostLineItem, addr ShippingAddress, shipOpt ShippingLevel) (Cost, ShippingAddressValidation, error)

	// Print creates a new print job.
	//
	// 	contact: Email address that should be contacted if
	// 	questions regarding the Print-Job arise. Lulu recommends to
	// 	use the email of a person who is responsible for placing
	// 	the Print-Job like a developer or business owner.
	//
	// 	externalId: Arbitrary string to identify and connect a
	// 	print job to your systems. Set it to an order number, a
	// 	purchase order or whatever else works for your particular
	// 	use case.
	//
	// 	productionDelay: Delay before a newly created Print-Job is
	// 	sent to production. Must be
	// 	[[MinProductionDelay],[MaxProductionDelay]]. This gives
	// 	some time for the order to be cancelled before the books
	// 	are printed. Once production has started, orders cannot be
	// 	canceled anymore.
	//
	// 	addr: The postal address of the customer that the order
	// 	will be sent to.
	//
	// 	shipOpt: Shipping method.
	//
	// 	items: List of books to print.
	//
	// https://api.lulu.com/docs/#tag/Print-Jobs/operation/Print-Jobs_create
	Print(contact EmailAddress, externalId string, productionDelay time.Duration, addr ShippingAddress, shipOpt ShippingLevel, items []Printable) (PrintJob, error)

	// Reprint creates a print job, printing books whose PrintableIds are
	// known from (one or more) prior calls to [Client.Print].
	//
	// https://api.lulu.com/docs/#tag/Print-Jobs/operation/Print-Jobs_reprint
	Reprint(contact EmailAddress, externalId string, productionDelay time.Duration, addr ShippingAddress, shipOpt ShippingLevel, items []Reprintable) (PrintJob, error)

	// Job retrieves the print job with the given ID, which is a
	// [PrintJob.Id] returned by [Client.Print] or [Client.Reprint].
	//
	// https://api.lulu.com/docs/#tag/Print-Jobs/operation/Print-Jobs_read
	Job(id uint64) (PrintJob, error)

	// Jobs retrieves a list of all print jobs that have been created,
	// filtered by a set of optional query parameters.
	//
	// https://api.lulu.com/docs/#tag/Print-Jobs/operation/Print-Jobs_list
	Jobs(queries ...PrintJobQuery) ([]PrintJob, error)

	// Cancel cancels the print job with the given ID. jobId is from a
	// [PrintJob] returned by [Client.Print] or [Client.Reprint].
	//
	// https://api.lulu.com/docs/#tag/Print-Jobs/operation/Print-Jobs_status_cancel
	Cancel(jobId uint64) error
}

// ValidateInterior starts a server-side validation job for the given
// interior file and polls its status until it finishes or the context
// expires. See [Client.StartInteriorValidation], [Client.GetInteriorValidation],
// and [PollPeriod].
func ValidateInterior(ctx context.Context, c Client, srcUrl string, mfg PkgId) (InteriorValidation, error) {
	id, err := c.StartInteriorValidation(srcUrl, mfg)
	if err != nil {
		return InteriorValidation{}, err
	}
	return pollInteriorValidation(ctx, c, id, InteriorStatusNormalized)
}

// ValidateInteriorBasic is like [Client.ValidateInterior] but without the
// optional pod_package_id.
func ValidateInteriorBasic(ctx context.Context, c Client, srcUrl string) (InteriorValidation, error) {
	id, err := c.StartInteriorValidationBasic(srcUrl)
	if err != nil {
		return InteriorValidation{}, err
	}
	return pollInteriorValidation(ctx, c, id, InteriorStatusValidated)
}

func pollInteriorValidation(ctx context.Context, c Client, id uint, wantStatus InteriorValidationStatus) (InteriorValidation, error) {
	return poll(ctx, func() (InteriorValidation, bool, error) {
		val, err := c.GetInteriorValidation(id)
		done := val.Status == wantStatus ||
			val.Status == InteriorStatusError
		return val, done, err
	})
}

// ValidateCover starts a server-side validation job for the given
// cover file and polls its status until it finishes or the context
// expires. See [Client.StartCoverValidation],
// [Client.GetCoverValidation], and [PollPeriod].
func ValidateCover(ctx context.Context, c Client, srcUrl string, mfg PkgId, npages uint) (CoverValidation, error) {
	id, err := c.StartCoverValidation(srcUrl, mfg, npages)
	if err != nil {
		return CoverValidation{}, err
	}
	return poll(ctx, func() (CoverValidation, bool, error) {
		val, err := c.GetCoverValidation(id)
		return val, val.Status.IsFinal(), err
	})
}

type client struct {
	ctx        context.Context
	c          *http.Client
	apiUrl     string
	keyPageUrl string
}

// Credentials contains the client-key and client-secret used to
// authenticate to the API.
type Credentials struct {
	Key, Secret string
}

// NewClient creates a client that will use creds to connect to the
// production API server.
//
// ctx is used by the OAuth2 client. If you don't care about this, use
// [context.Background]. See [clientcredentials.Config.Client].
func NewClient(ctx context.Context, creds Credentials) (Client, error) {
	return newClient(ctx, creds, production, productionKeyPage)
}

// NewClient creates a client that will connect to the sandbox API
// server. See [NewClient].
func NewSandboxClient(ctx context.Context, creds Credentials) (Client, error) {
	return newClient(ctx, creds, sandbox, sandboxKeyPage)
}

func newClient(ctx context.Context, creds Credentials, apiUrl, keyPageUrl string) (*client, error) {
	tokenUrl, err := url.JoinPath(apiUrl, tokenPath)
	if err != nil {
		return nil, pkgErrf(err, "error creating client")
	}

	cfg := &clientcredentials.Config{
		ClientID:     creds.Key,
		ClientSecret: creds.Secret,
		TokenURL:     tokenUrl,
	}
	return &client{ctx, cfg.Client(ctx), apiUrl, keyPageUrl}, nil
}

func (c *client) StartInteriorValidation(srcUrl string, mfg PkgId) (uint, error) {
	id, err := c.startInteriorValidation(validateInteriorReq{srcUrl, mfg})
	if err != nil {
		return 0, pkgErr(err)
	}
	return id, nil
}

func (c *client) StartInteriorValidationBasic(srcUrl string) (uint, error) {
	id, err := c.startInteriorValidation(validateInteriorBasicReq{srcUrl})
	if err != nil {
		return 0, pkgErr(err)
	}
	return id, nil
}

func (c *client) startInteriorValidation(payload any) (uint, error) {
	var val InteriorValidation
	err := c.postDecode(validateInteriorPath, payload, http.StatusCreated, &val)
	return val.Id, err
}

func (c *client) GetInteriorValidation(id uint) (InteriorValidation, error) {
	path, err := url.JoinPath(validateInteriorPath, fmt.Sprint(id))
	if err != nil {
		return InteriorValidation{}, pkgErr(err)
	}
	var val InteriorValidation
	if err := c.getDecode(path, &val); err != nil {
		return InteriorValidation{}, pkgErr(err)
	}
	return val, nil
}

func (c *client) CoverDimensions(mfg PkgId, npages uint, unit Unit) (CoverDimensions, error) {
	payload := coverDimensionsReq{mfg, npages, unit}
	var dims CoverDimensions
	err := c.postDecode(coverDimensionsPath, payload, http.StatusCreated, &dims)
	if err != nil {
		return CoverDimensions{}, pkgErr(err)
	}
	return dims, nil
}

func (c *client) StartCoverValidation(srcUrl string, mfg PkgId, npages uint) (uint, error) {
	payload := validateCoverReq{srcUrl, mfg, npages}
	var val CoverValidation
	err := c.postDecode(validateCoverPath, payload, http.StatusCreated, &val)
	if err != nil {
		return 0, pkgErr(err)
	}
	return val.Id, nil
}

func (c *client) GetCoverValidation(id uint) (CoverValidation, error) {
	path, err := url.JoinPath(validateCoverPath, fmt.Sprint(id))
	if err != nil {
		return CoverValidation{}, pkgErr(err)
	}
	var val CoverValidation
	if err := c.getDecode(path, &val); err != nil {
		return CoverValidation{}, pkgErr(err)
	}
	return val, nil
}

func (c *client) Cost(items []CostLineItem, addr ShippingAddress, shipOpt ShippingLevel) (Cost, ShippingAddressValidation, error) {
	payload := costReq{items, addr, shipOpt}
	var resp costResp
	err := c.postDecode(printJobCostPath, payload, http.StatusCreated, &resp)
	if err != nil {
		return Cost{}, ShippingAddressValidation{}, pkgErr(err)
	}
	return resp.cost(), resp.AddressValidation, nil
}

func (c *client) Print(contact EmailAddress, externalId string, productionDelay time.Duration, addr ShippingAddress, shipOpt ShippingLevel, items []Printable) (PrintJob, error) {
	job, err := print(c, contact, externalId, productionDelay, addr, shipOpt, items)
	if err != nil {
		err = pkgErr(err)
	}
	return job, err
}

func (c *client) Reprint(contact EmailAddress, externalId string, productionDelay time.Duration, addr ShippingAddress, shipOpt ShippingLevel, items []Reprintable) (PrintJob, error) {
	job, err := print(c, contact, externalId, productionDelay, addr, shipOpt, items)
	if err != nil {
		err = pkgErr(err)
	}
	return job, err
}

func print[P Printable | Reprintable](c *client, contact EmailAddress, externalId string, productionDelay time.Duration, addr ShippingAddress, shipOpt ShippingLevel, items []P) (PrintJob, error) {
	if err := verifyProductionDelay(productionDelay); err != nil {
		return PrintJob{}, err
	}
	req := printReq[P]{
		Contact:             contact,
		ExternalId:          externalId,
		Items:               items,
		ProductionDelayMins: uint(productionDelay.Round(time.Minute).Minutes()),
		ShipAddr:            addr,
		ShipOpt:             shipOpt,
	}
	var job PrintJob
	err := c.postDecode(printJobsPath, req, http.StatusCreated, &job)
	return job, err
}

func verifyProductionDelay(delay time.Duration) error {
	if delay < MinProductionDelay || delay > MaxProductionDelay {
		return fmt.Errorf("production delay %s out of range: must be [%s, %s]",
			delay, MinProductionDelay, MaxProductionDelay)
	}
	return nil
}

func (c *client) Job(id uint64) (PrintJob, error) {
	var job PrintJob
	path, err := url.JoinPath(printJobsPath, fmt.Sprint(id))
	if err != nil {
		return job, pkgErr(err)
	}
	if err := c.getDecode(path, &job); err != nil {
		return job, pkgErr(err)
	}
	return job, nil
}

func (c *client) Jobs(queries ...PrintJobQuery) ([]PrintJob, error) {
	var q printJobQueries
	q.apply(queries...)
	qvals := q.vals()

	var jobs []PrintJob
	var cnt uint
	for page := 1; ; page++ {
		qvals.Set("page", fmt.Sprint(page))
		var resp jobsResp
		if err := c.getQueryDecode(printJobsPath, qvals, &resp); err != nil {
			return jobs, pkgErr(err)
		}

		cnt = resp.Count
		if len(resp.Results) == 0 && resp.Next != "" {
			return jobs, pkgErr(fmt.Errorf("no results on this page, but server returned a next page: %s", resp.Next))
		}
		if len(resp.Results) > 0 {
			jobs = append(jobs, resp.Results...)
		}
		if len(resp.Results) == 0 || len(resp.Next) == 0 {
			break
		}
	}
	if uint(len(jobs)) != cnt {
		return jobs, pkgErr(fmt.Errorf("expected %d jobs, got %d", cnt, len(jobs)))
	}
	return jobs, nil
}

func (c *client) Cancel(jobId uint64) error {
	path, err := url.JoinPath(printJobsPath, fmt.Sprint(jobId), "status")
	if err != nil {
		return pkgErr(err)
	}
	req := map[string]OrderStatus{"name": OrderCanceled}
	var status PrintJobStatus
	if err := c.putDecode(path, req, &status); err != nil {
		return pkgErr(err)
	}
	if status.Status != OrderCanceled {
		return pkgErr(fmt.Errorf("cancel job %d: expected %s, got %s", jobId, OrderCanceled, status.Status))
	}
	return nil
}

// getDecode sends a GET request and unmarshals the response.
func (c *client) getDecode(path string, v any) error {
	return c.getQueryDecode(path, url.Values{}, v)
}

// getQueryDecode sends a GET path?query request and unmarshals the response into v.
func (c *client) getQueryDecode(path string, query url.Values, v any) error {
	url, err := c.url(path)
	if err != nil {
		return err
	}
	url += "?" + query.Encode()

	resp, err := c.c.Get(url)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return errRespStatus{resp}
	}
	return decodeResponse(resp, v)
}

// postDecode sends a POST request and unmarshals the response.
func (c *client) postDecode(path string, payload any, wantStatus int, v any) error {
	resp, err := c.post(path, payload)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != wantStatus {
		return errRespStatus{resp}
	}
	return decodeResponse(resp, v)
}

func (c *client) post(path string, payload any) (*http.Response, error) {
	body, err := json.Marshal(payload)
	if err != nil {
		return nil, errEncReq{payload, path, err}
	}
	url, err := c.url(path)
	if err != nil {
		return nil, err
	}

	debugf("POST %s request: `%s`\n", url, body)

	return c.c.Post(url, "application/json", bytes.NewBuffer(body))
}

// putDecode sends a PUT request and unmarshals the response.
func (c *client) putDecode(path string, payload any, v any) error {
	body, err := json.Marshal(payload)
	if err != nil {
		return errEncReq{payload, path, err}
	}
	url, err := c.url(path)
	if err != nil {
		return err
	}

	debugf("PUT %s request: `%s`\n", url, body)

	req, err := http.NewRequest(http.MethodPut, url, bytes.NewBuffer(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := c.c.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return errRespStatus{resp}
	}
	return decodeResponse(resp, v)
}

func (c *client) url(path string) (string, error) {
	return url.JoinPath(c.apiUrl, path)
}

func decodeResponse(resp *http.Response, v any) error {
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return errReadResp{resp, err}
	}

	debugf("%s %s response: `%s`\n", resp.Request.Method, resp.Request.URL, body)

	if err := json.Unmarshal(body, v); err != nil {
		return errDecResp{resp, body, err}
	}
	return nil
}

func poll[T any](ctx context.Context, f func() (v T, done bool, err error)) (T, error) {
	timer := time.NewTimer(0)
	for {
		select {
		case <-timer.C:
			v, done, err := f()
			if err != nil {
				return v, err
			} else if done {
				return v, nil
			}
			timer.Reset(PollPeriod)
		case <-ctx.Done():
			var v T
			return v, ctx.Err()
		}
	}
}