// 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

// Unit is a unit of length measurement.
type Unit string

const (
	Points      Unit = "pt"
	Millimeters      = "mm"
	Inches           = "inch"
)

type ValidationStatus string

const (
	StatusNull        ValidationStatus = "NULL"        // file validation is not started yet
	StatusValidating  ValidationStatus = "VALIDATING"  // file validation is still running
	StatusValidated   ValidationStatus = "VALIDATED"   // file validation finished without any errors
	StatusNormalizing ValidationStatus = "NORMALIZING" // file normalization (next step of validation, available only if pod_package_id is was passed in the payload) is still running
	StatusNormalized  ValidationStatus = "NORMALIZED"  // file normalization finished without any errors
	StatusError       ValidationStatus = "ERROR"       // file is invalid, list of errors is included in the response
)

func (s ValidationStatus) IsFinal() bool {
	switch s {
	case StatusValidated, StatusNormalized, StatusError:
		return true
	}
	return false
}

// validateInteriorReq is the json body of a /validate-interior/ request.
type validateInteriorReq struct {
	SrcUrl string `json:"source_url"`
	PkgId  PkgId  `json:"pod_package_id"`
}

// validateInteriorReq is the json body of a /validate-interior/ request without the optional pod_package_id.
type validateInteriorBasicReq struct {
	SrcUrl string `json:"source_url"`
}

// InteriorValidationRecord contains the validation status of an interior file.
type InteriorValidationRecord struct {
	Id          uint
	SrcUrl      string `json:"source_url"`
	NPages      uint   `json:"page_count"`
	Errors      string
	Status      ValidationStatus
	ValidPkgIds []PkgId `json:"valid_pod_package_ids"`
}

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, err
	}

	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) {
	return c.validateInterior(validateInteriorReq{srcUrl, mfg})
}

// 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) {
	return c.validateInterior(validateInteriorBasicReq{srcUrl})
}

func (c *Client) validateInterior(payload any) (uint, error) {
	body, err := json.Marshal(payload)
	if err != nil {
		return 0, fmt.Errorf("lulu: error encoding request body %v for %s: %w", payload, validateInteriorPath, err)
	}

	url, err := url.JoinPath(ApiUrl, validateInteriorPath)
	if err != nil {
		return 0, fmt.Errorf("lulu: %w", err)
	}
	resp, err := c.c.Post(url, "application/json", bytes.NewBuffer(body))
	if err != nil {
		return 0, fmt.Errorf("lulu: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusCreated {
		body, _ := io.ReadAll(resp.Body)
		return 0, fmt.Errorf("lulu: POST %s: %s: %s", url, resp.Status, body)
	}

	buf := new(bytes.Buffer)
	if _, err := io.Copy(buf, resp.Body); err != nil {
		return 0, fmt.Errorf("lulu: POST %s: error reading response body: %w", url, err)
	}
	dec := json.NewDecoder(buf)
	var rec InteriorValidationRecord
	if err := dec.Decode(&rec); err != nil {
		return 0, fmt.Errorf("lulu: POST %s: error decoding response body %q: %w", url, buf, err)
	}
	return rec.Id, nil
}

// 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) {
	url, err := url.JoinPath(ApiUrl, validateInteriorPath, fmt.Sprint(id))
	if err != nil {
		return InteriorValidationRecord{}, fmt.Errorf("lulu: %w", err)
	}
	resp, err := c.c.Get(url)
	if err != nil {
		return InteriorValidationRecord{}, fmt.Errorf("lulu: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return InteriorValidationRecord{}, fmt.Errorf("lulu: GET %s: %s: %s", url, resp.Status, body)
	}

	buf := new(bytes.Buffer)
	if _, err := io.Copy(buf, resp.Body); err != nil {
		return InteriorValidationRecord{}, fmt.Errorf("lulu: GET %s: error reading response body: %w", url, err)
	}
	dec := json.NewDecoder(buf)
	var rec InteriorValidationRecord
	if err := dec.Decode(&rec); err != nil {
		return rec, fmt.Errorf("lulu: GET %s: error decoding response body %q: %w", url, buf, err)
	}
	return rec, nil
}