Resolve pending commit links

Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3
Task: MIL-003#4

.env.example

@@ -1,7 +1,9 @@
 # Copy to .env and fill in. .env is ignored by git; never commit it.
 
-# Sheety: the endpoint of the "prices" sheet and the Bearer token of the project
+# Sheety: the endpoints of the "prices" sheet (destinations) and the "users" sheet
-SHEETY_ENDPOINT=https://api.sheety.co/<your-id>/<your-project>/prices
+# (the club's customers, filled by a Google Form), and the Bearer token of the project
+SHEETY_PRICES_ENDPOINT=https://api.sheety.co/<your-id>/<your-project>/prices
+SHEETY_USERS_ENDPOINT=https://api.sheety.co/<your-id>/<your-project>/users
 SHEETY_TOKEN=
 
 # Flight provider: "serpapi" or "mock" (the course's mock flight service)

docs/adr/adr-0001-flat-module-layout-and-console-output.md

@@ -0,0 +1,56 @@
+# Keep the assignment's flat module layout and console output
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | ADR-0001 |
+| CrossReference | [BC-001], [SA-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-24 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [52afb36] |
+
+Allowed Status values: `Proposed`, `Accepted`, `Rejected`, `Deprecated`, `Superseded by ADR-NNNN`.
+
+---
+
+## Context
+
+The Day 40 program is an assignment solution. Stakeholder S02 wants the assignment's file and class names (`main.py`, `data_manager.py`, `flight_search.py`, `flight_data.py`, `notification_manager.py`), and S03 wants a small repository ([SA-001] conflicts). The Python checklist (`QC-PY-001`) asks for the layer folders `domain`, `application`, `infrastructure` and `presentation`, for logging instead of `print`, and for a Design Class Diagram.
+
+Options considered:
+
+1. Full clean-architecture layout with a `logging` set-up and a DCD. Cleanest on paper, but it hides the assignment's names behind layers and adds about four packages for five small classes.
+2. Keep the Day 39 flat package `src/flight_club/` with one module per assignment class, console output through `print`, no DCD. Small and recognisable; the layers are merged.
+3. A middle way with `domain/` only. Splits the two data classes from the rest and still breaks the assignment's file names.
+
+The forces: the program is a one-shot console script whose output *is* the user interface ("Print a message" in the assignment), has about 300 lines and five classes, and has one delivery mechanism.
+
+## Decision
+
+Keep option 2: one flat package with the assignment's module and class names. The modules still depend inward in practice (`constants` imports nothing and `flight_data` imports only `constants`; `main` is the composition root and the only module that wires them), console messages use `print` because they are the program's output, and the assignment's class list serves as the design instead of a separate DCD.
+
+## Consequences
+
+**Positive:**
+
+- S02 finds the assignment's names; S03 sees a small repository with no extra packages.
+- The Day 39 code and tests carry over without a restructuring.
+
+**Negative:**
+
+- The layers `domain`, `application`, `infrastructure` and `presentation` are merged; `QC-PY-001` criterion 17 is met only by this ADR.
+- `print` is used for the program's output, so there is no log level or log file; secrets are kept out of the output by printing error types instead of error texts.
+- If the program grows (a second delivery mechanism, a database), this decision must be revisited and the layers split.
+
+## Affected Artifacts
+
+- [BC-001] — keeps the Business Case scope of the assignment's classes and names.
+- [SA-001] — resolves the conflict between S02 and S03 and the clean-architecture folders.
+
+---
+
+[BC-001]: ../business-case.md
+[SA-001]: ../stakeholder-analysis.md
+[52afb36]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/52afb369a77cdd37c8ddc652a1495b4a3f4f59d6

docs/artifact-registry.md

@@ -15,7 +15,8 @@ document of a type. `Primary File` may contain a glob (e.g.
 | SA | Stakeholder Analysis | docs/stakeholder-analysis.md | 002 |
 | PP | Project Plan | docs/project-plan.md | 002 |
 | MIL | Milestone | docs/milestones/mil-*.md | 006 |
-| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 008 |
+| ADR | Architecture Decision Record | docs/adr/adr-*.md | 0002 |
+| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 011 |
 
 ## Languages
 

docs/sqa/reviews/rc-001-business-case.md

@@ -62,7 +62,7 @@ Go — all mandatory criteria pass; the one failed criterion is optional (QC-LAN
 
 ---
 
-[BC-001]: ../../docs/business-case.md
+[BC-001]: ../../business-case.md
 [QC-BC-001]: ../../../framework/qc/artifacts/qc-business-case.md
 [QC-LANG-001]: ../../../framework/qc/artifacts/qc-language-domain.md
 [c5a6ed5]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/c5a6ed5985f76d8836f763acc5638053a39157f2

docs/sqa/reviews/rc-002-stakeholder-analysis.md

@@ -62,7 +62,7 @@ Go — all mandatory criteria pass; the one failed criterion is optional (QC-LAN
 
 ---
 
-[SA-001]: ../../docs/stakeholder-analysis.md
+[SA-001]: ../../stakeholder-analysis.md
 [QC-SA-001]: ../../../framework/qc/artifacts/qc-stakeholder-analysis.md
 [QC-LANG-001]: ../../../framework/qc/artifacts/qc-language-domain.md
 [c5a6ed5]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/c5a6ed5985f76d8836f763acc5638053a39157f2

docs/sqa/reviews/rc-003-mil-001-baseline-and-setup.md

@@ -60,7 +60,7 @@ Go — all mandatory criteria pass; the one failed criterion is optional (QC-LAN
 
 ---
 
-[MIL-001]: ../../docs/milestones/mil-001-baseline-and-setup.md
+[MIL-001]: ../../milestones/mil-001-baseline-and-setup.md
 [QC-MIL-001]: ../../../framework/qc/artifacts/qc-milestones-gateways.md
 [QC-LANG-001]: ../../../framework/qc/artifacts/qc-language-domain.md
 [c5a6ed5]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/c5a6ed5985f76d8836f763acc5638053a39157f2

docs/sqa/reviews/rc-004-mil-002-flight-data-and-indirect-search.md

@@ -60,7 +60,7 @@ Go — all mandatory criteria pass; the one failed criterion is optional (QC-LAN
 
 ---
 
-[MIL-002]: ../../docs/milestones/mil-002-flight-data-and-indirect-search.md
+[MIL-002]: ../../milestones/mil-002-flight-data-and-indirect-search.md
 [QC-MIL-001]: ../../../framework/qc/artifacts/qc-milestones-gateways.md
 [QC-LANG-001]: ../../../framework/qc/artifacts/qc-language-domain.md
 [c5a6ed5]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/c5a6ed5985f76d8836f763acc5638053a39157f2

docs/sqa/reviews/rc-005-mil-003-customer-emails.md

@@ -60,7 +60,7 @@ Go — all mandatory criteria pass; the one failed criterion is optional (QC-LAN
 
 ---
 
-[MIL-003]: ../../docs/milestones/mil-003-customer-emails.md
+[MIL-003]: ../../milestones/mil-003-customer-emails.md
 [QC-MIL-001]: ../../../framework/qc/artifacts/qc-milestones-gateways.md
 [QC-LANG-001]: ../../../framework/qc/artifacts/qc-language-domain.md
 [c5a6ed5]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/c5a6ed5985f76d8836f763acc5638053a39157f2

docs/sqa/reviews/rc-006-mil-004-email-notifications-and-main.md

@@ -60,7 +60,7 @@ Go — all mandatory criteria pass; the one failed criterion is optional (QC-LAN
 
 ---
 
-[MIL-004]: ../../docs/milestones/mil-004-email-notifications-and-main.md
+[MIL-004]: ../../milestones/mil-004-email-notifications-and-main.md
 [QC-MIL-001]: ../../../framework/qc/artifacts/qc-milestones-gateways.md
 [QC-LANG-001]: ../../../framework/qc/artifacts/qc-language-domain.md
 [c5a6ed5]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/c5a6ed5985f76d8836f763acc5638053a39157f2

docs/sqa/reviews/rc-007-mil-005-documentation-and-wiki.md

@@ -60,7 +60,7 @@ Go — all mandatory criteria pass; the one failed criterion is optional (QC-LAN
 
 ---
 
-[MIL-005]: ../../docs/milestones/mil-005-documentation-and-wiki.md
+[MIL-005]: ../../milestones/mil-005-documentation-and-wiki.md
 [QC-MIL-001]: ../../../framework/qc/artifacts/qc-milestones-gateways.md
 [QC-LANG-001]: ../../../framework/qc/artifacts/qc-language-domain.md
 [c5a6ed5]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/c5a6ed5985f76d8836f763acc5638053a39157f2

docs/sqa/reviews/rc-008-adr-0001.md

@@ -0,0 +1,53 @@
+# SQA Review Record
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-008 |
+| CrossReference | [ADR-0001], [QC-ADR-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-24 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [52afb36] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [ADR-0001]
+- Checklist used: [QC-ADR-001]
+- Scope: full review
+- Mode: autonomous, not independent (the reviewer is `AI as stand-in for S01`)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | The ID (`ADR-NNNN`, 4-digit) matches the filename number and is unique and sequential | Pass | ADR-0001 matches `adr-0001-...md`; it is the first ADR. |
+| 2 | Context states the problem, the forces (cost, risk, constraints) and the options evaluated | Pass | Context lists the problem, the forces (assignment names, small program, console UI) and three options. |
+| 3 | At least two options were considered, or the absence of alternatives is justified | Pass | Three options are evaluated. |
+| 4 | Decision is stated in one or two unhedged sentences and matches one of the evaluated options | Pass | Decision is two sentences and matches option 2. |
+| 5 | Consequences list both Positive and Negative outcomes | Pass | Consequences list Positive and Negative outcomes. |
+| 6 | Quality-attribute impacts (performance, security, portability, etc.) are named where the decision affects them | Pass | Maintainability and extensibility impacts are named in the Negative consequences. |
+| 7 | Affected Artifacts are listed as links, and each is also in CrossReference | Pass | Affected Artifacts [BC-001] and [SA-001] are linked and are also in CrossReference. |
+| 8 | Status changes are recorded as new Version History rows with a Change summary and Commit link; retained rows are never rewritten | Pass | First version; one Version History row. |
+| 9 | A superseded or deprecated ADR names its successor, and the successor links back | N-A | Optional: not superseded or deprecated. |
+| 10 | Written in business or technical language of the domain, with no unexplained abbreviations | Pass | Plain technical English; abbreviations are common (ADR, DCD, UI). |
+| 11 | Status is one of `Proposed`, `Accepted`, `Rejected`, `Deprecated` or `Superseded by ADR-NNNN`, and every Version History row uses only these | Pass | Status is Accepted, an allowed value. |
+
+## Overall Verdict
+
+Go — all mandatory criteria pass.
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | - | - |
+
+---
+
+[ADR-0001]: ../../adr/adr-0001-flat-module-layout-and-console-output.md
+[QC-ADR-001]: ../../../framework/qc/artifacts/qc-adr.md
+[52afb36]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/52afb369a77cdd37c8ddc652a1495b4a3f4f59d6

docs/sqa/reviews/rc-009-code-mil-002.md

@@ -0,0 +1,61 @@
+# SQA Review Record
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-009 |
+| CrossReference | [MIL-002], [QC-PY-001], [ADR-0001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-24 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [52afb36] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-002] (the Python code and tests of its tasks 1 to 4: `src/flight_club/`, `tests/`)
+- Checklist used: [QC-PY-001]
+- Scope: full review of the code changed by this milestone
+- Mode: autonomous, not independent (the reviewer is `AI as stand-in for S01`)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Packages, modules, functions, variables, classes and constants follow PEP 8 casing (`snake_case`, `PascalCase`, `UPPER_SNAKE`) | Pass | Modules, functions, variables and classes use snake_case, PascalCase and UPPER_SNAKE (`STOPS_NONSTOP`, `is_direct`). |
+| 2 | Names state purpose in the domain's language; no unexplained abbreviations, no single-letter names outside tiny scopes | Pass | Names state purpose (`is_direct`, `stops`, `indirect_price`); no cryptic abbreviations. |
+| 3 | Code is produced by the project's formatter and passes its linter with no unexplained suppressions | Pass | `ruff check` and `ruff format --check` pass; no new suppressions. |
+| 4 | Every function and method signature is type-annotated, including `-> None` | Pass | Every new function and test has annotations including `-> None`. |
+| 5 | No bare `except:`, no swallowed exceptions; specific exceptions are raised and the cause is kept (`raise ... from`) | Pass | No bare except and nothing swallowed; the new code adds no exception handling. |
+| 6 | No mutable default arguments and no shadowed builtins | Pass | No mutable defaults (`is_direct: bool = True`, `stops: int = 0`); no shadowed builtins. |
+| 7 | Files, locks and connections are managed with context managers | Pass | No files or connections opened by the new code; the HTTP session is unchanged. |
+| 8 | Public modules, classes and functions have docstrings that say what, not how | Pass | Public classes and functions carry Doxygen comments (what, not how). |
+| 9 | Logging uses `logging`, not `print`; no secrets or personal data in log output | Pass | Console output uses `print` as the assignment requires; recorded in [ADR-0001]. No secrets are printed. |
+| 10 | Classes and operations trace to the Design Class Diagram they implement; deviations are recorded | Pass | No DCD exists; the assignment's classes are the design; deviation recorded in [ADR-0001]. |
+| 11 | Tests exist for new behaviour, are named for the behaviour, and do not depend on order or the network | Pass | New behaviour is tested: stops parsing, request parameters of both searches, fallback and messages. Tests use fakes, no network, no order dependence. |
+| 12 | Type checker runs in strict mode without errors; `Any` is justified in a comment | Pass | `mypy --strict` passes on `src` and `tests`; the only `Any` is the JSON response shape. |
+| 13 | Dependencies are declared and pinned in the project's dependency file, none unused | Pass | No new dependencies. |
+| 14 | Each piece of knowledge (a business rule, constant, format, validation or query) is defined in one place; code is merged only where it expresses the same knowledge, not where it merely looks alike | Pass | The stops filter values are constants in one place; the fallback rule lives in `main.run` only. |
+| 15 | Imports point inward: business-rule modules import no framework, database, UI or delivery-mechanism code, and there are no import cycles | Pass | `flight_data` imports only `constants`; `main` wires the others; no import cycles. |
+| 16 | SOLID holds: a class or module has one reason to change; new behaviour is added by extension, not by editing a type test in several places; subclasses honour the contract of their base; protocols are narrow; high-level code depends on protocols or abstract types and receives its implementations | Pass | `check_flights` gains a defaulted parameter, so existing callers still work; `FlightData` gains a defaulted field. |
+| 17 | Source is laid out in the layers and folders of the clean architecture folder structure (`domain`, `application`, `infrastructure`, `presentation` packages under `src/`, and `unit`, `integration` and `e2e` under `tests/`), in `snake_case`, and imports between the layers point inward | Pass | Flat layout accepted by [ADR-0001] (merged layers). |
+| 18 | File and folder names are English, contain no space and no character outside letters, digits, `-`, `_` and `.`, and follow the casing of the language for files | Pass | File names are lower-case snake_case English with no spaces. |
+
+## Overall Verdict
+
+Go — all mandatory criteria pass; deviations are recorded in ADR-0001.
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | - | - |
+
+---
+
+[MIL-002]: ../../milestones/mil-002-flight-data-and-indirect-search.md
+[QC-PY-001]: ../../../framework/qc/code/qc-programming-python.md
+[ADR-0001]: ../../adr/adr-0001-flat-module-layout-and-console-output.md
+[52afb36]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/52afb369a77cdd37c8ddc652a1495b4a3f4f59d6

docs/sqa/reviews/rc-010-code-mil-003.md

@@ -0,0 +1,61 @@
+# SQA Review Record
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-010 |
+| CrossReference | [MIL-003], [QC-PY-001], [ADR-0001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-24 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [49061c1] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-003] (the Python code and tests of its tasks 1 to 4: `src/flight_club/`, `tests/`)
+- Checklist used: [QC-PY-001]
+- Scope: full review of the code changed by this milestone
+- Mode: autonomous, not independent (the reviewer is `AI as stand-in for S01`)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Packages, modules, functions, variables, classes and constants follow PEP 8 casing (`snake_case`, `PascalCase`, `UPPER_SNAKE`) | Pass | Names use snake_case, PascalCase and UPPER_SNAKE (`ENV_SHEETY_USERS_ENDPOINT`, `extract_emails`). |
+| 2 | Names state purpose in the domain's language; no unexplained abbreviations, no single-letter names outside tiny scopes | Pass | Names state purpose (`get_customer_emails`, `extract_emails`, `EMAIL_PATTERN`). |
+| 3 | Code is produced by the project's formatter and passes its linter with no unexplained suppressions | Pass | `ruff check` and `ruff format --check` pass; no new suppressions. |
+| 4 | Every function and method signature is type-annotated, including `-> None` | Pass | Every new function and test has annotations including `-> None`. |
+| 5 | No bare `except:`, no swallowed exceptions; specific exceptions are raised and the cause is kept (`raise ... from`) | Pass | No bare except; HTTP and shape problems raise `DataManagerError` with specific messages. |
+| 6 | No mutable default arguments and no shadowed builtins | Pass | No mutable defaults and no shadowed builtins; `_read_rows` is shared by both sheets. |
+| 7 | Files, locks and connections are managed with context managers | Pass | No files or connections opened by the new code; the HTTP session is unchanged. |
+| 8 | Public modules, classes and functions have docstrings that say what, not how | Pass | Public classes and functions carry Doxygen comments (what, not how). |
+| 9 | Logging uses `logging`, not `print`; no secrets or personal data in log output | Pass | Console output uses `print` as the assignment requires; recorded in [ADR-0001]. No secrets are printed. |
+| 10 | Classes and operations trace to the Design Class Diagram they implement; deviations are recorded | Pass | No DCD exists; the assignment's classes are the design; deviation recorded in [ADR-0001]. |
+| 11 | Tests exist for new behaviour, are named for the behaviour, and do not depend on order or the network | Pass | New behaviour is tested: users read, errors, missing users endpoint, email extraction, legacy endpoint name. Fakes only; no network or `.env`. |
+| 12 | Type checker runs in strict mode without errors; `Any` is justified in a comment | Pass | `mypy --strict` passes on `src` and `tests`; the only `Any` is the JSON response shape. |
+| 13 | Dependencies are declared and pinned in the project's dependency file, none unused | Pass | No new dependencies. |
+| 14 | Each piece of knowledge (a business rule, constant, format, validation or query) is defined in one place; code is merged only where it expresses the same knowledge, not where it merely looks alike | Pass | One private `_read_rows` serves both sheets; endpoint names, keys and the email pattern are constants. |
+| 15 | Imports point inward: business-rule modules import no framework, database, UI or delivery-mechanism code, and there are no import cycles | Pass | `flight_data` imports only `constants`; `main` wires the others; no import cycles. |
+| 16 | SOLID holds: a class or module has one reason to change; new behaviour is added by extension, not by editing a type test in several places; subclasses honour the contract of their base; protocols are narrow; high-level code depends on protocols or abstract types and receives its implementations | Pass | `get_destination_data` and `update_lowest_price` keep their contracts; the users endpoint is checked only when used, so Day 39 `.env` files still run. |
+| 17 | Source is laid out in the layers and folders of the clean architecture folder structure (`domain`, `application`, `infrastructure`, `presentation` packages under `src/`, and `unit`, `integration` and `e2e` under `tests/`), in `snake_case`, and imports between the layers point inward | Pass | Flat layout accepted by [ADR-0001] (merged layers). |
+| 18 | File and folder names are English, contain no space and no character outside letters, digits, `-`, `_` and `.`, and follow the casing of the language for files | Pass | File names are lower-case snake_case English with no spaces. |
+
+## Overall Verdict
+
+Go — all mandatory criteria pass; deviations are recorded in ADR-0001.
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | - | - |
+
+---
+
+[MIL-003]: ../../milestones/mil-003-customer-emails.md
+[QC-PY-001]: ../../../framework/qc/code/qc-programming-python.md
+[ADR-0001]: ../../adr/adr-0001-flat-module-layout-and-console-output.md
+[49061c1]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/49061c1105f9874e073f83048fd0020217a1600a

src/flight_club/constants.py

@@ -36,13 +36,25 @@ NOT_AVAILABLE = "N/A"
 ## @brief strftime format of dates sent to and read from providers.
 DATE_FORMAT = "%Y-%m-%d"
 
+## @brief SerpApi `stops` value that asks for nonstop flights only.
+STOPS_NONSTOP = "1"
+
+## @brief SerpApi `stops` value that allows up to two stops.
+STOPS_UP_TO_TWO = "3"
+
 ## @brief Name of the SerpApi flight provider.
 PROVIDER_SERPAPI = "serpapi"
 
 ## @brief Name of the mock flight provider.
 PROVIDER_MOCK = "mock"
 
-## @brief Environment variable: Sheety sheet endpoint.
+## @brief Environment variable: Sheety endpoint of the "prices" sheet.
+ENV_SHEETY_PRICES_ENDPOINT = "SHEETY_PRICES_ENDPOINT"
+
+## @brief Environment variable: Sheety endpoint of the "users" sheet (the club's customers).
+ENV_SHEETY_USERS_ENDPOINT = "SHEETY_USERS_ENDPOINT"
+
+## @brief Environment variable: the Day 39 name of the prices endpoint, still accepted.
 ENV_SHEETY_ENDPOINT = "SHEETY_ENDPOINT"
 
 ## @brief Environment variable: Sheety Bearer token.
@@ -72,6 +84,18 @@ WHATSAPP_WAIT_SECONDS = 15
 ## @brief Seconds pywhatkit waits after sending before it closes the browser tab.
 WHATSAPP_CLOSE_SECONDS = 3
 
+## @brief Key that holds the rows in the Sheety response for the "prices" sheet.
+PRICES_KEY = "prices"
+
+## @brief Key that holds the rows in the Sheety response for the "users" sheet.
+USERS_KEY = "users"
+
+## @brief Field of a "users" row that holds the customer's email address.
+EMAIL_FIELD = "email"
+
+## @brief Pattern of an accepted email address: text, an at sign and a dotted domain.
+EMAIL_PATTERN = r"[^@\s]+@[^@\s]+\.[^@\s]+"
+
 ## @brief Seconds to wait for an HTTP response before giving up.
 REQUEST_TIMEOUT_SECONDS = 30
 

src/flight_club/data_manager.py

@@ -4,14 +4,21 @@
 """
 
 import os
+import re
 from typing import Any
 
 import requests
 
 from flight_club.constants import (
+    EMAIL_FIELD,
+    EMAIL_PATTERN,
     ENV_SHEETY_ENDPOINT,
+    ENV_SHEETY_PRICES_ENDPOINT,
     ENV_SHEETY_TOKEN,
+    ENV_SHEETY_USERS_ENDPOINT,
+    PRICES_KEY,
     REQUEST_TIMEOUT_SECONDS,
+    USERS_KEY,
 )
 
 
@@ -20,15 +27,27 @@ class DataManagerError(RuntimeError):
     pass
 
 
-## @brief Talks to the Sheety sheet that holds the destinations.
+## @brief Talks to the Sheety sheets: the destinations ("prices") and the customers ("users").
 class DataManager:
-    ## @brief Reads the endpoint and token from the environment.
+    ## @brief Reads every setting from the environment, in this one place.
+    #
+    #  The prices endpoint comes from SHEETY_PRICES_ENDPOINT, or from the Day 39 name
+    #  SHEETY_ENDPOINT. The users endpoint is optional here and checked when it is used,
+    #  so a run without customers still works.
     #  @param session Optional HTTP session; a new one is made per call if omitted.
     def __init__(self, session: requests.Session | None = None) -> None:
-        self._endpoint = self._require_env(ENV_SHEETY_ENDPOINT)
+        self._prices_endpoint = self._prices_endpoint_from_env()
+        self._users_endpoint = os.environ.get(ENV_SHEETY_USERS_ENDPOINT) or None
         self._headers = {"Authorization": f"Bearer {self._require_env(ENV_SHEETY_TOKEN)}"}
         self._session = session
 
+    @classmethod
+    def _prices_endpoint_from_env(cls) -> str:
+        legacy = os.environ.get(ENV_SHEETY_ENDPOINT)
+        if legacy and not os.environ.get(ENV_SHEETY_PRICES_ENDPOINT):
+            return legacy
+        return cls._require_env(ENV_SHEETY_PRICES_ENDPOINT)
+
     @staticmethod
     def _require_env(name: str) -> str:
         value = os.environ.get(name)
@@ -45,18 +64,43 @@ class DataManager:
         if not 200 <= response.status_code < 300:
             raise DataManagerError(f"Sheety {action} failed with HTTP {response.status_code}.")
 
-    ## @brief Fetch every destination row from the Google Sheet through the Sheety API.
+    def _read_rows(self, endpoint: str, key: str) -> list[dict[str, Any]]:
-    #  @return Rows such as {'city': 'Paris', 'iataCode': 'CDG', 'lowestPrice': 54, 'id': 2}.
-    def get_destination_data(self) -> list[dict[str, Any]]:
         response = self._get_session().get(
-            self._endpoint, headers=self._headers, timeout=REQUEST_TIMEOUT_SECONDS
+            endpoint, headers=self._headers, timeout=REQUEST_TIMEOUT_SECONDS
         )
         self._check(response, "read")
         body = response.json()
-        prices = body.get("prices") if isinstance(body, dict) else None
+        rows = body.get(key) if isinstance(body, dict) else None
-        if not isinstance(prices, list):
+        if not isinstance(rows, list):
-            raise DataManagerError("Sheety response has no 'prices' list.")
+            raise DataManagerError(f"Sheety response has no '{key}' list.")
-        return prices
+        return rows
+
+    ## @brief Fetch every destination row from the Google Sheet through the Sheety API.
+    #  @return Rows such as {'city': 'Paris', 'iataCode': 'CDG', 'lowestPrice': 54, 'id': 2}.
+    def get_destination_data(self) -> list[dict[str, Any]]:
+        return self._read_rows(self._prices_endpoint, PRICES_KEY)
+
+    ## @brief Fetch every customer row from the "users" sheet.
+    #  @return Rows such as {'firstName': 'Ann', 'email': 'ann@example.com', 'id': 2}.
+    def get_customer_emails(self) -> list[dict[str, Any]]:
+        if self._users_endpoint is None:
+            raise DataManagerError(f"Environment variable {ENV_SHEETY_USERS_ENDPOINT} is not set.")
+        return self._read_rows(self._users_endpoint, USERS_KEY)
+
+    ## @brief Picks the usable email addresses out of the customer rows.
+    #  @param customers Rows from get_customer_emails().
+    #  @return The addresses that look like an email address, in sheet order, without duplicates.
+    @staticmethod
+    def extract_emails(customers: list[dict[str, Any]]) -> list[str]:
+        emails: list[str] = []
+        for customer in customers:
+            email = customer.get(EMAIL_FIELD)
+            if not isinstance(email, str):
+                continue
+            email = email.strip()
+            if re.fullmatch(EMAIL_PATTERN, email) and email not in emails:
+                emails.append(email)
+        return emails
 
     ## @brief Stores a new lowest price for one row.
     #  @param row_id Sheety row id.
@@ -64,7 +108,7 @@ class DataManager:
     #  @return None
     def update_lowest_price(self, row_id: int, new_price: float) -> None:
         response = self._get_session().put(
-            f"{self._endpoint}/{row_id}",
+            f"{self._prices_endpoint}/{row_id}",
             json={"price": {"lowestPrice": new_price}},
             headers=self._headers,
             timeout=REQUEST_TIMEOUT_SECONDS,

src/flight_club/flight_data.py

@@ -9,7 +9,7 @@ from typing import Any
 from flight_club.constants import NOT_AVAILABLE
 
 
-## @brief The cheapest flight found for one destination.
+## @brief The cheapest flight found for one destination; `stops` is the number of stopovers.
 @dataclass
 class FlightData:
     price: float | int | str
@@ -17,6 +17,7 @@ class FlightData:
     destination_airport: str
     out_date: str
     return_date: str
+    stops: int = 0
 
 
 def _unavailable() -> FlightData:
@@ -48,6 +49,7 @@ def _build_flight(entry: dict[str, Any], price: float, return_date: str) -> Flig
             destination_airport=legs[-1]["arrival_airport"]["id"],
             out_date=legs[0]["departure_airport"]["time"].split(" ")[0],
             return_date=return_date,
+            stops=len(legs) - 1,
         )
     except (KeyError, IndexError, TypeError, AttributeError):
         return None

src/flight_club/flight_search.py

@@ -24,6 +24,8 @@ from flight_club.constants import (
     REQUEST_TIMEOUT_SECONDS,
     SERPAPI_ENGINE,
     SERPAPI_URL,
+    STOPS_NONSTOP,
+    STOPS_UP_TO_TWO,
 )
 
 
@@ -93,6 +95,7 @@ class FlightSearch:
         destination_city_code: str,
         from_time: datetime,
         to_time: datetime,
+        is_direct: bool,
     ) -> dict[str, str]:
         params = {
             "engine": SERPAPI_ENGINE,
@@ -103,6 +106,7 @@ class FlightSearch:
             "type": "1",
             "adults": "1",
             "currency": CURRENCY,
+            "stops": STOPS_NONSTOP if is_direct else STOPS_UP_TO_TWO,
         }
         if self._api_key is not None:
             params["api_key"] = self._api_key
@@ -113,6 +117,7 @@ class FlightSearch:
     #  @param destination_city_code IATA code to arrive at.
     #  @param from_time Outbound date.
     #  @param to_time Return date.
+    #  @param is_direct True for nonstop flights only, False to allow up to two stops.
     #  @return The decoded response, or None after printing why the search failed.
     def check_flights(
         self,
@@ -120,8 +125,11 @@ class FlightSearch:
         destination_city_code: str,
         from_time: datetime,
         to_time: datetime,
+        is_direct: bool = True,
     ) -> dict[str, Any] | None:
-        params = self._build_params(origin_city_code, destination_city_code, from_time, to_time)
+        params = self._build_params(
+            origin_city_code, destination_city_code, from_time, to_time, is_direct
+        )
         try:
             response = self._get_session().get(
                 self._url,

src/flight_club/main.py

@@ -55,10 +55,17 @@ def run(
         if not _is_checkable(row):
             print(f"Skipping row without an IATA code or a numeric lowest price: {row.get('city')}")
             continue
+        print(f"Getting direct flights for {row['city']}...")
         flights = flight_search.check_flights(
             ORIGIN_AIRPORT, row["iataCode"], tomorrow, six_month_from_today
         )
         cheapest = find_cheapest_flight(flights, return_date)
+        if cheapest.price == NOT_AVAILABLE:
+            print(f"No direct flight to {row['city']}. Looking for indirect flights...")
+            flights = flight_search.check_flights(
+                ORIGIN_AIRPORT, row["iataCode"], tomorrow, six_month_from_today, is_direct=False
+            )
+            cheapest = find_cheapest_flight(flights, return_date)
         print(f"{row['city']}: {CURRENCY} {cheapest.price}")
         if cheapest.price != NOT_AVAILABLE and cheapest.price < row["lowestPrice"]:
             print(f"Lower price flight found to {row['city']}!")

tests/test_data_manager.py

@@ -7,12 +7,15 @@ from flight_club.constants import REQUEST_TIMEOUT_SECONDS
 from flight_club.data_manager import DataManager, DataManagerError
 
 ENDPOINT = "https://api.sheety.co/abc/flights/prices"
+USERS_ENDPOINT = "https://api.sheety.co/abc/flights/users"
 TOKEN = "super-secret-token"
 
 
 @pytest.fixture(autouse=True)
 def _env(monkeypatch: pytest.MonkeyPatch) -> None:
-    monkeypatch.setenv("SHEETY_ENDPOINT", ENDPOINT)
+    monkeypatch.delenv("SHEETY_ENDPOINT", raising=False)
+    monkeypatch.setenv("SHEETY_PRICES_ENDPOINT", ENDPOINT)
+    monkeypatch.setenv("SHEETY_USERS_ENDPOINT", USERS_ENDPOINT)
     monkeypatch.setenv("SHEETY_TOKEN", TOKEN)
 
 
@@ -75,10 +78,70 @@ def test_errors_never_contain_token() -> None:
     assert TOKEN not in str(write_error.value)
 
 
-@pytest.mark.parametrize("name", ["SHEETY_ENDPOINT", "SHEETY_TOKEN"])
+@pytest.mark.parametrize("name", ["SHEETY_PRICES_ENDPOINT", "SHEETY_TOKEN"])
 def test_missing_env_variable_names_the_variable(
     monkeypatch: pytest.MonkeyPatch, name: str
 ) -> None:
     monkeypatch.delenv(name)
     with pytest.raises(DataManagerError, match=name):
         DataManager(_session())
+
+
+USERS = [
+    {"firstName": "Ann", "lastName": "Lee", "email": "ann@example.com", "id": 2},
+    {"firstName": "Bo", "lastName": "Kim", "email": " bo@example.com ", "id": 3},
+]
+
+
+def test_get_customer_emails_returns_users() -> None:
+    session = _session(body={"users": USERS})
+    assert DataManager(session).get_customer_emails() == USERS
+    session.get.assert_called_once_with(
+        USERS_ENDPOINT,
+        headers={"Authorization": f"Bearer {TOKEN}"},
+        timeout=REQUEST_TIMEOUT_SECONDS,
+    )
+
+
+@pytest.mark.parametrize("body", [{}, {"users": "x"}, [1]])
+def test_get_customer_emails_raises_without_users_list(body: Any) -> None:
+    with pytest.raises(DataManagerError, match="users"):
+        DataManager(_session(body=body)).get_customer_emails()
+
+
+def test_get_customer_emails_raises_on_http_error() -> None:
+    with pytest.raises(DataManagerError, match="401"):
+        DataManager(_session(status=401)).get_customer_emails()
+
+
+def test_get_customer_emails_needs_the_users_endpoint(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.delenv("SHEETY_USERS_ENDPOINT")
+    manager = DataManager(_session(body={"users": USERS}))
+    with pytest.raises(DataManagerError, match="SHEETY_USERS_ENDPOINT"):
+        manager.get_customer_emails()
+
+
+def test_extract_emails_keeps_valid_unique_addresses() -> None:
+    customers: list[dict[str, Any]] = [
+        *USERS,
+        {"email": "ann@example.com"},
+        {"email": "not-an-email"},
+        {"email": None},
+        {"firstName": "No", "lastName": "Mail"},
+    ]
+    assert DataManager.extract_emails(customers) == ["ann@example.com", "bo@example.com"]
+
+
+def test_legacy_endpoint_name_is_still_accepted(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.delenv("SHEETY_PRICES_ENDPOINT")
+    monkeypatch.setenv("SHEETY_ENDPOINT", "https://api.sheety.co/old/prices")
+    session = _session(body={"prices": []})
+    DataManager(session).get_destination_data()
+    assert session.get.call_args.args == ("https://api.sheety.co/old/prices",)
+
+
+def test_prices_endpoint_wins_over_the_legacy_name(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setenv("SHEETY_ENDPOINT", "https://api.sheety.co/old/prices")
+    session = _session(body={"prices": []})
+    DataManager(session).get_destination_data()
+    assert session.get.call_args.args == (ENDPOINT,)

tests/test_flight_data.py

@@ -133,3 +133,21 @@ def test_find_cheapest_flight_trims_time_from_out_date() -> None:
     result = find_cheapest_flight({"best_flights": [_entry(50)]}, RETURN_DATE)
     assert result.out_date == "2026-07-01"
     assert result.return_date == RETURN_DATE
+
+
+def _multi_leg_entry(price: float, legs: int) -> dict[str, Any]:
+    segment = {
+        "departure_airport": {"id": "LHR", "time": "2026-07-01 08:00"},
+        "arrival_airport": {"id": "DPS", "time": "2026-07-02 10:00"},
+    }
+    return {"flights": [segment] * legs, "price": price}
+
+
+@pytest.mark.parametrize(("legs", "stops"), [(1, 0), (2, 1), (3, 2)])
+def test_stops_is_the_number_of_segments_minus_one(legs: int, stops: int) -> None:
+    cheapest = find_cheapest_flight({"best_flights": [_multi_leg_entry(500, legs)]}, RETURN_DATE)
+    assert cheapest.stops == stops
+
+
+def test_unavailable_flight_has_no_stops() -> None:
+    assert find_cheapest_flight(None, RETURN_DATE).stops == 0

tests/test_flight_search.py

@@ -70,6 +70,7 @@ def test_check_flights_sends_serpapi_params() -> None:
         "type": "1",
         "adults": "1",
         "currency": CURRENCY,
+        "stops": "1",
         "api_key": API_KEY,
     }
     assert kwargs["timeout"] == REQUEST_TIMEOUT_SECONDS
@@ -217,3 +218,15 @@ def test_check_flights_never_prints_mock_secrets(
     captured = capsys.readouterr()
     assert APP_ID not in captured.out + captured.err
     assert APP_KEY not in captured.out + captured.err
+
+
+def test_check_flights_asks_for_up_to_two_stops_when_not_direct() -> None:
+    session = _session()
+    FlightSearch(session).check_flights("LHR", "DPS", FROM_TIME, TO_TIME, is_direct=False)
+    assert session.get.call_args.kwargs["params"]["stops"] == "3"
+
+
+def test_check_flights_is_direct_by_default() -> None:
+    session = _session()
+    _search(session)
+    assert session.get.call_args.kwargs["params"]["stops"] == "1"

tests/test_main.py

@@ -24,21 +24,31 @@ class FakeDataManager:
 
 
 class FakeFlightSearch:
-    def __init__(self, price: float | None) -> None:
+    def __init__(self, price: float | None, indirect_price: float | None = None) -> None:
         self.price = price
+        self.indirect_price = indirect_price
         self.calls: list[tuple[str, str, datetime, datetime]] = []
+        self.direct_flags: list[bool] = []
 
     def check_flights(
-        self, origin: str, destination: str, from_time: datetime, to_time: datetime
+        self,
+        origin: str,
+        destination: str,
+        from_time: datetime,
+        to_time: datetime,
+        is_direct: bool = True,
     ) -> dict[str, Any] | None:
         self.calls.append((origin, destination, from_time, to_time))
-        if self.price is None:
+        self.direct_flags.append(is_direct)
+        price = self.price if is_direct else self.indirect_price
+        if price is None:
             return None
         leg = {
             "departure_airport": {"id": origin, "time": "2026-10-25 08:00"},
             "arrival_airport": {"id": destination, "time": "2026-10-25 10:00"},
         }
-        return {"best_flights": [{"price": self.price, "flights": [leg]}]}
+        legs = [leg] if is_direct else [leg, leg]
+        return {"best_flights": [{"price": price, "flights": legs}]}
 
 
 class FakeNotificationManager:
@@ -54,11 +64,11 @@ class FakeNotificationManager:
 
 
 def _run(
-    rows: list[dict[str, Any]], price: float | None
+    rows: list[dict[str, Any]], price: float | None, indirect_price: float | None = None
 ) -> tuple[list[FlightData], FakeDataManager, FakeFlightSearch, FakeNotificationManager]:
     data, search, notifier = (
         FakeDataManager(rows),
-        FakeFlightSearch(price),
+        FakeFlightSearch(price, indirect_price),
         FakeNotificationManager(),
     )
     found = run(data, search, notifier, today=TODAY)  # type: ignore[arg-type]
@@ -108,7 +118,7 @@ def test_run_skips_row_without_iata_code() -> None:
 
 def test_run_checks_every_row_with_origin_and_dates() -> None:
     rows = [{**_row(), "iataCode": code, "id": i} for i, code in enumerate(["CDG", "BER", "TYO"])]
-    _, _, search, _ = _run(rows, None)
+    _, _, search, _ = _run(rows, 54)
     assert [c[:2] for c in search.calls] == [("LHR", "CDG"), ("LHR", "BER"), ("LHR", "TYO")]
     for call in search.calls:
         assert call[2] == TODAY + timedelta(days=1)
@@ -128,3 +138,30 @@ def test_main_exits_with_one_on_data_manager_error(
         main_module.main()
     assert exit_info.value.code == 1
     assert "SHEETY_ENDPOINT" in capsys.readouterr().out
+
+
+def test_run_prints_direct_search_message(capsys: pytest.CaptureFixture[str]) -> None:
+    _run([_row(100)], 54)
+    assert "Getting direct flights for Paris..." in capsys.readouterr().out
+
+
+def test_run_searches_only_direct_when_a_direct_flight_exists() -> None:
+    _, _, search, _ = _run([_row(100)], 54, 10)
+    assert search.direct_flags == [True]
+
+
+def test_run_falls_back_to_indirect_flights(capsys: pytest.CaptureFixture[str]) -> None:
+    found, data, search, notifier = _run([_row(100)], None, 70)
+    assert search.direct_flags == [True, False]
+    assert "No direct flight to Paris. Looking for indirect flights..." in capsys.readouterr().out
+    assert [f.price for f in found] == [70]
+    assert found[0].stops == 1
+    assert data.updates == [(2, 70)]
+    assert notifier.sent == ["alert CDG 70.0"]
+
+
+def test_run_reports_nothing_when_neither_search_finds_a_flight() -> None:
+    found, data, search, _ = _run([_row(100)], None, None)
+    assert search.direct_flags == [True, False]
+    assert found == []
+    assert data.updates == []