From d4521934ce342ebba4e32f4b3b9fb569d08fff61 Mon Sep 17 00:00:00 2001 From: 1e99 Date: Sat, 22 Mar 2025 13:19:55 +0100 Subject: [PATCH] first commit --- LICENSE.md | 355 ++++++++++++++++++++++++++++++++++++++++++ cron.go | 66 ++++++++ devices/devices.go | 6 + devices/raspi-gpio.go | 5 + devices/test.go | 31 ++++ example.sh | 23 +++ go.mod | 3 + index.tmpl | 83 ++++++++++ main.go | 59 +++++++ routes/api.go | 45 ++++++ routes/index.go | 72 +++++++++ sessions/mem.go | 74 +++++++++ sessions/sessions.go | 23 +++ 13 files changed, 845 insertions(+) create mode 100644 LICENSE.md create mode 100644 cron.go create mode 100644 devices/devices.go create mode 100644 devices/raspi-gpio.go create mode 100644 devices/test.go create mode 100755 example.sh create mode 100644 go.mod create mode 100644 index.tmpl create mode 100644 main.go create mode 100644 routes/api.go create mode 100644 routes/index.go create mode 100644 sessions/mem.go create mode 100644 sessions/sessions.go diff --git a/LICENSE.md b/LICENSE.md new file mode 100644 index 0000000..cd44203 --- /dev/null +++ b/LICENSE.md @@ -0,0 +1,355 @@ +Mozilla Public License Version 2.0 +================================== + +### 1. Definitions + +**1.1. “Contributor”** + means each individual or legal entity that creates, contributes to + the creation of, or owns Covered Software. + +**1.2. “Contributor Version”** + means the combination of the Contributions of others (if any) used + by a Contributor and that particular Contributor's Contribution. + +**1.3. “Contribution”** + means Covered Software of a particular Contributor. + +**1.4. “Covered Software”** + means Source Code Form to which the initial Contributor has attached + the notice in Exhibit A, the Executable Form of such Source Code + Form, and Modifications of such Source Code Form, in each case + including portions thereof. + +**1.5. “Incompatible With Secondary Licenses”** + means + +* **(a)** that the initial Contributor has attached the notice described + in Exhibit B to the Covered Software; or +* **(b)** that the Covered Software was made available under the terms of + version 1.1 or earlier of the License, but not also under the + terms of a Secondary License. + +**1.6. “Executable Form”** + means any form of the work other than Source Code Form. + +**1.7. “Larger Work”** + means a work that combines Covered Software with other material, in + a separate file or files, that is not Covered Software. + +**1.8. “License”** + means this document. + +**1.9. “Licensable”** + means having the right to grant, to the maximum extent possible, + whether at the time of the initial grant or subsequently, any and + all of the rights conveyed by this License. + +**1.10. “Modifications”** + means any of the following: + +* **(a)** any file in Source Code Form that results from an addition to, + deletion from, or modification of the contents of Covered + Software; or +* **(b)** any new file in Source Code Form that contains any Covered + Software. + +**1.11. “Patent Claims” of a Contributor** + means any patent claim(s), including without limitation, method, + process, and apparatus claims, in any patent Licensable by such + Contributor that would be infringed, but for the grant of the + License, by the making, using, selling, offering for sale, having + made, import, or transfer of either its Contributions or its + Contributor Version. + +**1.12. “Secondary License”** + means either the GNU General Public License, Version 2.0, the GNU + Lesser General Public License, Version 2.1, the GNU Affero General + Public License, Version 3.0, or any later versions of those + licenses. + +**1.13. “Source Code Form”** + means the form of the work preferred for making modifications. + +**1.14. “You” (or “Your”)** + means an individual or a legal entity exercising rights under this + License. For legal entities, “You” includes any entity that + controls, is controlled by, or is under common control with You. For + purposes of this definition, “control” means **(a)** the power, direct + or indirect, to cause the direction or management of such entity, + whether by contract or otherwise, or **(b)** ownership of more than + fifty percent (50%) of the outstanding shares or beneficial + ownership of such entity. + + +### 2. License Grants and Conditions + +#### 2.1. Grants + +Each Contributor hereby grants You a world-wide, royalty-free, +non-exclusive license: + +* **(a)** under intellectual property rights (other than patent or trademark) + Licensable by such Contributor to use, reproduce, make available, + modify, display, perform, distribute, and otherwise exploit its + Contributions, either on an unmodified basis, with Modifications, or + as part of a Larger Work; and +* **(b)** under Patent Claims of such Contributor to make, use, sell, offer + for sale, have made, import, and otherwise transfer either its + Contributions or its Contributor Version. + +#### 2.2. Effective Date + +The licenses granted in Section 2.1 with respect to any Contribution +become effective for each Contribution on the date the Contributor first +distributes such Contribution. + +#### 2.3. Limitations on Grant Scope + +The licenses granted in this Section 2 are the only rights granted under +this License. No additional rights or licenses will be implied from the +distribution or licensing of Covered Software under this License. +Notwithstanding Section 2.1(b) above, no patent license is granted by a +Contributor: + +* **(a)** for any code that a Contributor has removed from Covered Software; + or +* **(b)** for infringements caused by: **(i)** Your and any other third party's + modifications of Covered Software, or **(ii)** the combination of its + Contributions with other software (except as part of its Contributor + Version); or +* **(c)** under Patent Claims infringed by Covered Software in the absence of + its Contributions. + +This License does not grant any rights in the trademarks, service marks, +or logos of any Contributor (except as may be necessary to comply with +the notice requirements in Section 3.4). + +#### 2.4. Subsequent Licenses + +No Contributor makes additional grants as a result of Your choice to +distribute the Covered Software under a subsequent version of this +License (see Section 10.2) or under the terms of a Secondary License (if +permitted under the terms of Section 3.3). + +#### 2.5. Representation + +Each Contributor represents that the Contributor believes its +Contributions are its original creation(s) or it has sufficient rights +to grant the rights to its Contributions conveyed by this License. + +#### 2.6. Fair Use + +This License is not intended to limit any rights You have under +applicable copyright doctrines of fair use, fair dealing, or other +equivalents. + +#### 2.7. Conditions + +Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted +in Section 2.1. + + +### 3. Responsibilities + +#### 3.1. Distribution of Source Form + +All distribution of Covered Software in Source Code Form, including any +Modifications that You create or to which You contribute, must be under +the terms of this License. You must inform recipients that the Source +Code Form of the Covered Software is governed by the terms of this +License, and how they can obtain a copy of this License. You may not +attempt to alter or restrict the recipients' rights in the Source Code +Form. + +#### 3.2. Distribution of Executable Form + +If You distribute Covered Software in Executable Form then: + +* **(a)** such Covered Software must also be made available in Source Code + Form, as described in Section 3.1, and You must inform recipients of + the Executable Form how they can obtain a copy of such Source Code + Form by reasonable means in a timely manner, at a charge no more + than the cost of distribution to the recipient; and + +* **(b)** You may distribute such Executable Form under the terms of this + License, or sublicense it under different terms, provided that the + license for the Executable Form does not attempt to limit or alter + the recipients' rights in the Source Code Form under this License. + +#### 3.3. Distribution of a Larger Work + +You may create and distribute a Larger Work under terms of Your choice, +provided that You also comply with the requirements of this License for +the Covered Software. If the Larger Work is a combination of Covered +Software with a work governed by one or more Secondary Licenses, and the +Covered Software is not Incompatible With Secondary Licenses, this +License permits You to additionally distribute such Covered Software +under the terms of such Secondary License(s), so that the recipient of +the Larger Work may, at their option, further distribute the Covered +Software under the terms of either this License or such Secondary +License(s). + +#### 3.4. Notices + +You may not remove or alter the substance of any license notices +(including copyright notices, patent notices, disclaimers of warranty, +or limitations of liability) contained within the Source Code Form of +the Covered Software, except that You may alter any license notices to +the extent required to remedy known factual inaccuracies. + +#### 3.5. Application of Additional Terms + +You may choose to offer, and to charge a fee for, warranty, support, +indemnity or liability obligations to one or more recipients of Covered +Software. However, You may do so only on Your own behalf, and not on +behalf of any Contributor. You must make it absolutely clear that any +such warranty, support, indemnity, or liability obligation is offered by +You alone, and You hereby agree to indemnify every Contributor for any +liability incurred by such Contributor as a result of warranty, support, +indemnity or liability terms You offer. You may include additional +disclaimers of warranty and limitations of liability specific to any +jurisdiction. + + +### 4. Inability to Comply Due to Statute or Regulation + +If it is impossible for You to comply with any of the terms of this +License with respect to some or all of the Covered Software due to +statute, judicial order, or regulation then You must: **(a)** comply with +the terms of this License to the maximum extent possible; and **(b)** +describe the limitations and the code they affect. Such description must +be placed in a text file included with all distributions of the Covered +Software under this License. Except to the extent prohibited by statute +or regulation, such description must be sufficiently detailed for a +recipient of ordinary skill to be able to understand it. + + +### 5. Termination + +**5.1.** The rights granted under this License will terminate automatically +if You fail to comply with any of its terms. However, if You become +compliant, then the rights granted under this License from a particular +Contributor are reinstated **(a)** provisionally, unless and until such +Contributor explicitly and finally terminates Your grants, and **(b)** on an +ongoing basis, if such Contributor fails to notify You of the +non-compliance by some reasonable means prior to 60 days after You have +come back into compliance. Moreover, Your grants from a particular +Contributor are reinstated on an ongoing basis if such Contributor +notifies You of the non-compliance by some reasonable means, this is the +first time You have received notice of non-compliance with this License +from such Contributor, and You become compliant prior to 30 days after +Your receipt of the notice. + +**5.2.** If You initiate litigation against any entity by asserting a patent +infringement claim (excluding declaratory judgment actions, +counter-claims, and cross-claims) alleging that a Contributor Version +directly or indirectly infringes any patent, then the rights granted to +You by any and all Contributors for the Covered Software under Section +2.1 of this License shall terminate. + +**5.3.** In the event of termination under Sections 5.1 or 5.2 above, all +end user license agreements (excluding distributors and resellers) which +have been validly granted by You or Your distributors under this License +prior to termination shall survive termination. + + +### 6. Disclaimer of Warranty + +> Covered Software is provided under this License on an “as is” +> basis, without warranty of any kind, either expressed, implied, or +> statutory, including, without limitation, warranties that the +> Covered Software is free of defects, merchantable, fit for a +> particular purpose or non-infringing. The entire risk as to the +> quality and performance of the Covered Software is with You. +> Should any Covered Software prove defective in any respect, You +> (not any Contributor) assume the cost of any necessary servicing, +> repair, or correction. This disclaimer of warranty constitutes an +> essential part of this License. No use of any Covered Software is +> authorized under this License except under this disclaimer. + +### 7. Limitation of Liability + +> Under no circumstances and under no legal theory, whether tort +> (including negligence), contract, or otherwise, shall any +> Contributor, or anyone who distributes Covered Software as +> permitted above, be liable to You for any direct, indirect, +> special, incidental, or consequential damages of any character +> including, without limitation, damages for lost profits, loss of +> goodwill, work stoppage, computer failure or malfunction, or any +> and all other commercial damages or losses, even if such party +> shall have been informed of the possibility of such damages. This +> limitation of liability shall not apply to liability for death or +> personal injury resulting from such party's negligence to the +> extent applicable law prohibits such limitation. Some +> jurisdictions do not allow the exclusion or limitation of +> incidental or consequential damages, so this exclusion and +> limitation may not apply to You. + + +### 8. Litigation + +Any litigation relating to this License may be brought only in the +courts of a jurisdiction where the defendant maintains its principal +place of business and such litigation shall be governed by laws of that +jurisdiction, without reference to its conflict-of-law provisions. +Nothing in this Section shall prevent a party's ability to bring +cross-claims or counter-claims. + + +### 9. Miscellaneous + +This License represents the complete agreement concerning the subject +matter hereof. If any provision of this License is held to be +unenforceable, such provision shall be reformed only to the extent +necessary to make it enforceable. Any law or regulation which provides +that the language of a contract shall be construed against the drafter +shall not be used to construe this License against a Contributor. + + +### 10. Versions of the License + +#### 10.1. New Versions + +Mozilla Foundation is the license steward. Except as provided in Section +10.3, no one other than the license steward has the right to modify or +publish new versions of this License. Each version will be given a +distinguishing version number. + +#### 10.2. Effect of New Versions + +You may distribute the Covered Software under the terms of the version +of the License under which You originally received the Covered Software, +or under the terms of any subsequent version published by the license +steward. + +#### 10.3. Modified Versions + +If you create software not governed by this License, and you want to +create a new license for such software, you may create and use a +modified version of this License if you rename the license and remove +any references to the name of the license steward (except to note that +such modified license differs from this License). + +#### 10.4. Distributing Source Code Form that is Incompatible With Secondary Licenses + +If You choose to distribute Source Code Form that is Incompatible With +Secondary Licenses under the terms of this version of the License, the +notice described in Exhibit B of this License must be attached. + +## Exhibit A - Source Code Form License Notice + + This Source Code Form is subject to the terms of the Mozilla Public + License, v. 2.0. If a copy of the MPL was not distributed with this + file, You can obtain one at http://mozilla.org/MPL/2.0/. + +If it is not possible or desirable to put the notice in a particular +file, then You may include the notice in a location (such as a LICENSE +file in a relevant directory) where a recipient would be likely to look +for such a notice. + +You may add additional accurate notices of copyright ownership. + +## Exhibit B - “Incompatible With Secondary Licenses” Notice + + This Source Code Form is "Incompatible With Secondary Licenses", as + defined by the Mozilla Public License, v. 2.0. diff --git a/cron.go b/cron.go new file mode 100644 index 0000000..011e7e6 --- /dev/null +++ b/cron.go @@ -0,0 +1,66 @@ +package main + +import ( + "log" + "time" + + "git.1e99.eu/1e99/wolbodge/devices" + "git.1e99.eu/1e99/wolbodge/sessions" +) + +func DeviceCheck(logger *log.Logger, device devices.Device, wantStatus func() (bool, error), exit <-chan bool) { + for { + select { + case <-exit: + break + default: + status, err := device.Status() + if err != nil { + logger.Printf("Failed to fetch device status, waiting 1 minute until next attempt: %s", err) + time.Sleep(1 * time.Minute) + continue + } + + want, err := wantStatus() + if err != nil { + logger.Printf("Failed to fetch want status, waiting 1 minute until next attempt: %s", err) + time.Sleep(1 * time.Minute) + continue + } + + if status == want { + // Don't lock up our single-threaded session storage too much + time.Sleep(2 * time.Second) + continue + } + + err = device.PushPowerButton() + if err != nil { + logger.Printf("Failed to push power button, waiting 2 minutes until next attempt: %s", err) + // Cooldown to not overwhelm the device with start/stop requests + time.Sleep(2 * time.Minute) + return + } + + logger.Printf("Pushed power button") + time.Sleep(2 * time.Minute) + } + } +} + +func PruneStorage(logger *log.Logger, storage sessions.Storage, interval time.Duration, exit <-chan bool) { + for { + select { + case <-exit: + break + default: + /*pruned, err := storage.PruneTickets() + if err != nil { + logger.Printf("Failed to prune tickets: %s", err) + } + + logger.Printf("Pruned %d tickets", pruned) + time.Sleep(interval)*/ + } + } +} diff --git a/devices/devices.go b/devices/devices.go new file mode 100644 index 0000000..19eeb91 --- /dev/null +++ b/devices/devices.go @@ -0,0 +1,6 @@ +package devices + +type Device interface { + Status() (bool, error) + PushPowerButton() error +} diff --git a/devices/raspi-gpio.go b/devices/raspi-gpio.go new file mode 100644 index 0000000..400b72b --- /dev/null +++ b/devices/raspi-gpio.go @@ -0,0 +1,5 @@ +package devices + +func NewRaspiGPIO() Device { + return nil +} diff --git a/devices/test.go b/devices/test.go new file mode 100644 index 0000000..d714ab0 --- /dev/null +++ b/devices/test.go @@ -0,0 +1,31 @@ +package devices + +import "sync" + +func NewTest(initialStatus bool) Device { + device := &test{ + lock: sync.Mutex{}, + status: initialStatus, + } + return device +} + +type test struct { + lock sync.Mutex + status bool +} + +func (d *test) Status() (bool, error) { + d.lock.Lock() + defer d.lock.Unlock() + + return d.status, nil +} + +func (d *test) PushPowerButton() error { + d.lock.Lock() + defer d.lock.Unlock() + + d.status = !d.status + return nil +} diff --git a/example.sh b/example.sh new file mode 100755 index 0000000..df728a5 --- /dev/null +++ b/example.sh @@ -0,0 +1,23 @@ +#!/usr/bin/env sh +# Example for a backup script + +# Start a new session +session_id=$(curl -s -X POST -F "description=Daily backup" http://localhost:3000/api/session) +exit_code=$? +if [ $exit_code != 0 ]; then + echo "Failed to create session" + exit 1 +fi + +echo "Aquired session with id $session_id" + +# Do your backup here and wait for the PC to come online using a ping-loop for example +sleep 5 + +# Delete the session after we are done using it +curl -s -X DELETE http://localhost:3000/api/session/$session_id +exit_code=$? +if [ $exit_code != 0 ]; then + echo "Failed to delete session" + exit 1 +fi diff --git a/go.mod b/go.mod new file mode 100644 index 0000000..a0deefa --- /dev/null +++ b/go.mod @@ -0,0 +1,3 @@ +module git.1e99.eu/1e99/wolbodge + +go 1.23.2 diff --git a/index.tmpl b/index.tmpl new file mode 100644 index 0000000..f2c3eeb --- /dev/null +++ b/index.tmpl @@ -0,0 +1,83 @@ + + + + + WoLBodge + + + + + + + +
+
+
Status
+ +

+ {{ if .DeviceStatus }} + On + {{ else }} + Off + {{ end }} +

+
+ +
+
Start a new session
+ +
+ + + +
+
+ +

Active sessions

+ +
+ + + + + + + + + + + + {{ range $session := .Sessions }} + + + + + + + {{ end }} + +
IDDescriptionCreated atActions
{{ $session.Id }}{{ $session.Description }}{{ $session.CreatedAt.Format "02.01.2006 15:04:05" }} +
+ + +
+
+
+
+ + diff --git a/main.go b/main.go new file mode 100644 index 0000000..6f7a11f --- /dev/null +++ b/main.go @@ -0,0 +1,59 @@ +package main + +import ( + "fmt" + "html/template" + "log" + "net/http" + "time" + + "git.1e99.eu/1e99/wolbodge/devices" + "git.1e99.eu/1e99/wolbodge/routes" + "git.1e99.eu/1e99/wolbodge/sessions" + + _ "embed" +) + +//go:embed index.tmpl +var embed string + +func Run() error { + address := ":3000" + + tmpl := template.New("") + _, err := tmpl.Parse(embed) + if err != nil { + return fmt.Errorf("failed to parse template: %w", err) + } + + device := devices.NewTest(false) + storage := sessions.NewMemStorage() + logger := log.Default() + mux := http.NewServeMux() + + mux.Handle("GET /", routes.GetIndex(device, storage, tmpl)) + mux.Handle("POST /start_session", routes.StartSession(storage)) + mux.Handle("POST /end_session", routes.EndSession(storage)) + + mux.Handle("POST /api/session", routes.APIStartSession(storage)) + mux.Handle("DELETE /api/session/{session_id}", routes.APIEndSession(storage)) + + exit := make(chan bool) + go PruneStorage(logger, storage, 10*time.Second, exit) + go DeviceCheck(logger, device, storage.HasSessions, exit) + + logger.Printf("Listening on %s", address) + err = http.ListenAndServe(address, mux) + if err != nil { + return fmt.Errorf("failed to listen: %w", err) + } + + return nil +} + +func main() { + err := Run() + if err != nil { + log.Fatalf("%s", err) + } +} diff --git a/routes/api.go b/routes/api.go new file mode 100644 index 0000000..0883354 --- /dev/null +++ b/routes/api.go @@ -0,0 +1,45 @@ +package routes + +import ( + "fmt" + "net/http" + "strings" + "time" + + "git.1e99.eu/1e99/wolbodge/sessions" +) + +func APIStartSession(storage sessions.Storage) http.HandlerFunc { + return func(res http.ResponseWriter, req *http.Request) { + err := req.ParseMultipartForm(10 * 1024) + if err != nil { + http.Error(res, "", http.StatusBadRequest) + return + } + + description := req.FormValue("description") + if strings.TrimSpace(description) == "" { + description = "description" + } + + session, err := storage.StartSession(description, time.Now()) + if err != nil { + http.Error(res, "", http.StatusInternalServerError) + return + } + + fmt.Fprintf(res, "%s", session.Id) + } +} + +func APIEndSession(storage sessions.Storage) http.HandlerFunc { + return func(res http.ResponseWriter, req *http.Request) { + sessionId := req.PathValue("session_id") + + err := storage.EndSession(sessionId) + if err != nil { + http.Error(res, "", http.StatusInternalServerError) + return + } + } +} diff --git a/routes/index.go b/routes/index.go new file mode 100644 index 0000000..57fb8a8 --- /dev/null +++ b/routes/index.go @@ -0,0 +1,72 @@ +package routes + +import ( + "html/template" + "net/http" + "strings" + "time" + + "git.1e99.eu/1e99/wolbodge/devices" + "git.1e99.eu/1e99/wolbodge/sessions" +) + +func GetIndex(device devices.Device, storage sessions.Storage, tmpl *template.Template) http.HandlerFunc { + return func(res http.ResponseWriter, req *http.Request) { + status, err := device.Status() + if err != nil { + return + } + + sessions, err := storage.GetSessions() + if err != nil { + return + } + + tmpl.Execute(res, map[string]any{ + "DeviceStatus": status, + "Sessions": sessions, + }) + } +} + +func StartSession(storage sessions.Storage) http.HandlerFunc { + return func(res http.ResponseWriter, req *http.Request) { + err := req.ParseMultipartForm(10 * 1024) + if err != nil { + http.Error(res, "", http.StatusBadRequest) + return + } + + description := req.FormValue("description") + if strings.TrimSpace(description) == "" { + description = "unknown" + } + + _, err = storage.StartSession(description, time.Now()) + if err != nil { + http.Error(res, "", http.StatusInternalServerError) + return + } + + http.Redirect(res, req, "/", http.StatusFound) + } +} + +func EndSession(storage sessions.Storage) http.HandlerFunc { + return func(res http.ResponseWriter, req *http.Request) { + err := req.ParseMultipartForm(10 * 1024) + if err != nil { + http.Error(res, "", http.StatusBadRequest) + return + } + + sessionId := req.FormValue("session_id") + err = storage.EndSession(sessionId) + if err != nil { + http.Error(res, "", http.StatusInternalServerError) + return + } + + http.Redirect(res, req, "/", http.StatusFound) + } +} diff --git a/sessions/mem.go b/sessions/mem.go new file mode 100644 index 0000000..a013159 --- /dev/null +++ b/sessions/mem.go @@ -0,0 +1,74 @@ +package sessions + +import ( + "strconv" + "sync" + "time" +) + +func NewMemStorage() Storage { + storage := &memStorage{ + sessions: make(map[string]Session), + idCounter: 0, + lock: sync.Mutex{}, + } + return storage +} + +type memStorage struct { + sessions map[string]Session + idCounter uint64 + lock sync.Mutex +} + +func (s *memStorage) HasSessions() (bool, error) { + s.lock.Lock() + defer s.lock.Unlock() + return len(s.sessions) > 0, nil +} + +func (s *memStorage) GetSessions() ([]Session, error) { + s.lock.Lock() + defer s.lock.Unlock() + + sessions := make([]Session, len(s.sessions)) + id := 0 + + for _, session := range s.sessions { + sessions[id] = session + id += 1 + } + + return sessions, nil +} + +func (s *memStorage) StartSession(description string, createdAt time.Time) (Session, error) { + s.lock.Lock() + defer s.lock.Unlock() + + rawId := s.idCounter + s.idCounter = rawId + 1 + id := strconv.FormatUint(rawId, 10) + + session := Session{ + Id: id, + Description: description, + CreatedAt: createdAt, + } + s.sessions[id] = session + + return session, nil +} + +func (s *memStorage) EndSession(id string) error { + s.lock.Lock() + defer s.lock.Unlock() + + _, found := s.sessions[id] + if !found { + //return ErrNotFound + } + + delete(s.sessions, id) + return nil +} diff --git a/sessions/sessions.go b/sessions/sessions.go new file mode 100644 index 0000000..401e9f5 --- /dev/null +++ b/sessions/sessions.go @@ -0,0 +1,23 @@ +package sessions + +import "time" + +type Session struct { + Id string + Description string + CreatedAt time.Time +} + +type Storage interface { + // Check if the storage contains any sessions + HasSessions() (bool, error) + + // List all sessions + GetSessions() ([]Session, error) + + // Start a new session + StartSession(description string, createdAt time.Time) (Session, error) + + // End an old session + EndSession(id string) error +}