Add write support for assignments (POST, PUT, DELETE)

api.go

@@ -1,6 +1,7 @@
 package forecast
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -25,6 +26,19 @@ func New(url string, accountID string, accessToken string) *API {
 	}
 }
 
+func (api *API) initClient() error {
+	if api.client == nil {
+		jar, err := cookiejar.New(nil)
+		if err != nil {
+			return err
+		}
+		api.client = &http.Client{
+			Jar: jar,
+		}
+	}
+	return nil
+}
+
 func get[T any](api *API, path string) (T, error) {
 	var result T
 	req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("%s/%s", api.URL, path), nil)
@@ -33,29 +47,79 @@ func get[T any](api *API, path string) (T, error) {
 	}
 	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", api.token))
 	req.Header.Set("Forecast-Account-ID", api.AccountID)
-	if api.client == nil {
-		jar, err := cookiejar.New(nil)
+	err = api.initClient()
+	if err != nil {
+		return result, err
+	}
+	r, err := api.client.Do(req)
+	if err != nil {
+		return result, err
+	}
+	defer r.Body.Close()
+	if r.StatusCode >= http.StatusBadRequest {
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			return result, err
 		}
-		api.client = &http.Client{
-			Jar: jar,
-		}
+
+		return result, fmt.Errorf("%s: %s", r.Status, string(body))
+	}
+
+	err = json.NewDecoder(r.Body).Decode(&result)
+	return result, err
+}
+
+func mutate[TBody any, TResult any](api *API, method string, path string, content TBody) (TResult, error) {
+	var result TResult
+	b, err := json.Marshal(content)
+	if err != nil {
+		return result, err
+	}
+	req, err := http.NewRequest(method, fmt.Sprintf("%s/%s", api.URL, path), bytes.NewReader(b))
+	if err != nil {
+		return result, err
+	}
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", api.token))
+	req.Header.Set("Forecast-Account-ID", api.AccountID)
+	req.Header.Set("Content-Type", "application/json;charset=utf-8")
+
+	return doRequest[TResult](api, req)
+}
+
+func mutateNoBody(api *API, method string, path string) error {
+	req, err := http.NewRequest(method, fmt.Sprintf("%s/%s", api.URL, path), nil)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", api.token))
+	req.Header.Set("Forecast-Account-ID", api.AccountID)
+	_, err = doRequest[struct{}](api, req)
+	return err
+}
+
+func doRequest[T any](api *API, req *http.Request) (T, error) {
+	var result T
+	err := api.initClient()
+	if err != nil {
+		return result, err
 	}
 	r, err := api.client.Do(req)
 	if err != nil {
 		return result, err
 	}
+
 	defer r.Body.Close()
 	if r.StatusCode >= http.StatusBadRequest {
 		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			return result, err
 		}
-
 		return result, fmt.Errorf("%s: %s", r.Status, string(body))
 	}
 
 	err = json.NewDecoder(r.Body).Decode(&result)
+	if err == io.EOF { // empty response body, nothing to decode
+		err = nil
+	}
 	return result, err
 }

assignment.go

@@ -2,13 +2,18 @@ package forecast
 
 import (
 	"encoding/csv"
+	"fmt"
 	"io"
+	"net/http"
 	"net/url"
 	"strconv"
 	"strings"
 	"time"
 )
 
+type assignmentContainer struct {
+	Assignment Assignment `json:"assignment"`
+}
 type assignmentsContainer struct {
 	Assignments Assignments `json:"assignments"`
 }
@@ -33,6 +38,24 @@ type Assignment struct {
 	ActiveOnDaysOff         bool      `json:"active_on_days_off"`
 }
 
+type assignmentRequestContainer struct {
+	Assignment AssignmentRequest `json:"assignment"`
+}
+
+// AssignmentRequest is used as a payload when sending a mutation request for a Forecast assignment
+type AssignmentRequest struct {
+	StartDate               string `json:"start_date"`
+	EndDate                 string `json:"end_date"`
+	Allocation              *int   `json:"allocation"`
+	Notes                   string `json:"notes"`
+	HarvestProjectTaskID    *int   `json:"harvest_project_task_id"`
+	ProjectID               int    `json:"project_id"`
+	PersonID                int    `json:"person_id"`
+	PlaceholderID           *int   `json:"placeholder_id"`
+	RepeatedAssignmentSetID *int   `json:"repeated_assignment_set_id"`
+	ActiveOnDaysOff         bool   `json:"active_on_days_off"`
+}
+
 // AssignmentFilter is used to filter assignments
 type AssignmentFilter struct {
 	ProjectID               int
@@ -135,6 +158,36 @@ func (api *API) AssignmentsWithFilter(filter AssignmentFilter) (Assignments, err
 	return container.Assignments, nil
 }
 
+// CreateAssignment creates a new assignment on the Forecast account
+// A PersonID of '0' will include "Everyone"
+func (api *API) CreateAssignment(assignment AssignmentRequest) (Assignment, error) {
+	if assignment.ProjectID < 1 {
+		return Assignment{}, fmt.Errorf("unable to create assignment - project_id is not valid")
+	}
+	aContainer, err := mutate[assignmentRequestContainer, assignmentContainer](api, http.MethodPost, "assignments", assignmentRequestContainer{Assignment: assignment})
+	return aContainer.Assignment, err
+}
+
+// UpdateAssignment updates an existing assignment on the Forecast account
+func (api *API) UpdateAssignment(assignment AssignmentRequest, assignmentID int) (Assignment, error) {
+	if assignment.ProjectID < 1 {
+		return Assignment{}, fmt.Errorf("unable to update assignment - project_id is not valid")
+	}
+	if assignmentID < 1 {
+		return Assignment{}, fmt.Errorf("unable to update assignment - assignment_id is not valid")
+	}
+	aContainer, err := mutate[assignmentRequestContainer, assignmentContainer](api, http.MethodPut, fmt.Sprintf("assignments/%d", assignmentID), assignmentRequestContainer{Assignment: assignment})
+	return aContainer.Assignment, err
+}
+
+// DeleteAssignment deletes an assignment on the Forecast account
+func (api *API) DeleteAssignment(assignmentID int) error {
+	if assignmentID < 1 {
+		return fmt.Errorf("unable to delete assignment - assignment_id is not valid")
+	}
+	return mutateNoBody(api, http.MethodDelete, fmt.Sprintf("assignments/%d", assignmentID))
+}
+
 // ToParams formats url.Values as a string
 func ToParams(values url.Values) string {
 	if len(values) == 0 {