// 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"

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

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

	tokenPath            = "/auth/realms/glasstree/protocol/openid-connect/token"
	validateInteriorPath = "/validate-interior"
	coverDimensionsPath  = "/cover-dimensions"
	validateCoverPath    = "/validate-cover"
)

// ApiUrl is the location of the API server. It is set to the sandbox
// environment by default; change it to the production environment when
// you are ready to deploy.
var ApiUrl = SandboxUrl

type Client struct {
	c *http.Client
}

// NewClient returns a client that will use the given client-key and
// client-secret to connect to the API server.
func NewClient(ctx context.Context, key, secret string) (*Client, error) {
	tokenUrl, err := url.JoinPath(ApiUrl, tokenPath)
	if err != nil {
		return nil, pkgErrf(err, "error creating client")
	}

	cfg := &clientcredentials.Config{
		ClientID:     key,
		ClientSecret: secret,
		TokenURL:     tokenUrl,
	}
	return &Client{cfg.Client(ctx)}, nil
}

// ValidateInterior 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 GetInteriorValidation() to poll the
// status of the job.
//
// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Interior_create
func (c *Client) ValidateInterior(srcUrl string, mfg PkgId) (uint, error) {
	id, err := c.validateInterior(validateInteriorReq{srcUrl, mfg})
	if err != nil {
		return 0, pkgErr(err)
	}
	return id, nil
}

// ValidateInteriorBasic is like ValidateInterior but without the
// optional pod_package_id.
//
// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Interior_create
func (c *Client) ValidateInteriorBasic(srcUrl string) (uint, error) {
	id, err := c.validateInterior(validateInteriorBasicReq{srcUrl})
	if err != nil {
		return 0, pkgErr(err)
	}
	return id, nil
}

func (c *Client) validateInterior(payload any) (uint, error) {
	var rec InteriorValidationRecord
	err := c.postDecode(validateInteriorPath, payload, http.StatusCreated, &rec)
	return rec.Id, err
}

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

// 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
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
}

// ValidateCover 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
// GetCoverValidation() to poll the status of the job.
//
// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Cover_create
func (c *Client) ValidateCover(srcUrl string, mfg PkgId, npages uint) (uint, error) {
	payload := validateCoverReq{srcUrl, mfg, npages}
	var rec CoverValidationRecord
	err := c.postDecode(validateCoverPath, payload, http.StatusCreated, &rec)
	if err != nil {
		return 0, pkgErr(err)
	}
	return rec.Id, nil
}

// GetCoverValidiation retrieves information about a cover file
// validation job that was started by ValidiateCover().
//
// https://api.lulu.com/docs/#tag/Files-validation/operation/Validate-Cover_read
func (c *Client) GetCoverValidation(id uint) (CoverValidationRecord, error) {
	path, err := url.JoinPath(validateCoverPath, fmt.Sprint(id))
	if err != nil {
		return CoverValidationRecord{}, pkgErr(err)
	}
	var rec CoverValidationRecord
	if err := c.getDecode(path, &rec); err != nil {
		return CoverValidationRecord{}, pkgErr(err)
	}
	return rec, nil
}

func (c *Client) getDecode(path string, v any) error {
	url, err := url.JoinPath(ApiUrl, path)
	if err != nil {
		return err
	}
	resp, err := c.c.Get(url)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return errResp{resp}
	}
	return decodeResponse(resp, v)
}

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 errResp{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 := url.JoinPath(ApiUrl, path)
	if err != nil {
		return nil, err
	}
	return c.c.Post(url, "application/json", bytes.NewBuffer(body))
}

func decodeResponse(resp *http.Response, v any) error {
	buf := new(bytes.Buffer)
	if _, err := io.Copy(buf, resp.Body); err != nil {
		return errReadResp{resp, err}
	}
	dec := json.NewDecoder(buf)
	if err := dec.Decode(v); err != nil {
		return errDecResp{resp, buf.Bytes(), err}
	}
	return nil
}