implement GET /cover-dimensions

1 files changed, 85 insertions, 20 deletions

diff --git a/lulu.go b/lulu.go
index 2346749..af425f0 100644
--- a/lulu.go
+++ b/lulu.go
@@ -9,6 +9,7 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"strconv"
 
 	"golang.org/x/oauth2/clientcredentials"
 )
@@ -33,8 +34,8 @@ type Unit string
 
 const (
 	Points      Unit = "pt"
-	Millimeters      = "mm"
-	Inches           = "inch"
+	Millimeters Unit = "mm"
+	Inches      Unit = "inch"
 )
 
 type ValidationStatus string
@@ -77,6 +78,43 @@ type InteriorValidationRecord struct {
 	ValidPkgIds []PkgId `json:"valid_pod_package_ids"`
 }
 
+// coverDimensionsReq is the json body of a /cover-dimensions/ request.
+type coverDimensionsReq struct {
+	PkgId  PkgId `json:"pod_package_id"`
+	NPages uint  `json:"interior_page_count"`
+	Unit   Unit  `json:"unit"`
+}
+
+type CoverDimensions struct {
+	Width, Height float64
+	Unit          Unit
+}
+
+func (cd *CoverDimensions) UnmarshalJSON(data []byte) error {
+	s := string(data)
+	var alias struct {
+		Width, Height string
+		Unit          Unit
+	}
+	if err := json.Unmarshal(data, &alias); err != nil {
+		return fmt.Errorf("malformed %T: %q: %w", cd, s, err)
+	}
+
+	w, err := strconv.ParseFloat(alias.Width, 64)
+	if err != nil {
+		return fmt.Errorf("malformed %T.Width: %q: %w", cd, s, err)
+	}
+	h, err := strconv.ParseFloat(alias.Height, 64)
+	if err != nil {
+		return fmt.Errorf("malformed %T.Height: %q: %w", cd, s, err)
+	}
+
+	cd.Width = w
+	cd.Height = h
+	cd.Unit = alias.Unit
+	return nil
+}
+
 type Client struct {
 	c *http.Client
 }
@@ -132,20 +170,12 @@ func (c *Client) validateInterior(payload any) (uint, error) {
 	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)
+		return 0, errResp{resp}
 	}
 
-	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
+	err = decodeResponse(resp, &rec)
+	return rec.Id, err
 }
 
 // GetInteriorValidation retrieves information about an interior file
@@ -164,18 +194,53 @@ func (c *Client) GetInteriorValidation(id uint) (InteriorValidationRecord, error
 	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)
+		return InteriorValidationRecord{}, errResp{resp}
+	}
+
+	var rec InteriorValidationRecord
+	err = decodeResponse(resp, &rec)
+	return rec, err
+}
+
+// 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}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return CoverDimensions{}, fmt.Errorf("lulu: error encoding request body %v for %s: %w", payload, coverDimensionsPath, err)
+	}
+
+	url, err := url.JoinPath(ApiUrl, coverDimensionsPath)
+	if err != nil {
+		return CoverDimensions{}, fmt.Errorf("lulu: %w", err)
+	}
+	resp, err := c.c.Post(url, "application/json", bytes.NewBuffer(body))
+	if err != nil {
+		return CoverDimensions{}, fmt.Errorf("lulu: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusCreated {
+		return CoverDimensions{}, errResp{resp}
 	}
 
+	var dims CoverDimensions
+	err = decodeResponse(resp, &dims)
+	return dims, err
+}
+
+func decodeResponse(resp *http.Response, v any) error {
 	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)
+		return errReadResp{resp, 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)
+	if err := dec.Decode(v); err != nil {
+		return errDecResp{resp, buf.Bytes(), err}
 	}
-	return rec, nil
+	return nil
 }