Get an email alert when a competitor's price changes

flowchart TD trig(["scheduled price check"]):::trigtime s0[["Visit each tracked page"]]:::mi s1["Read price shown"]:::task s2["Compare to last known price"]:::task s3["Send email alert"]:::task trig --> s0 s0 --> s1 s1 --> s2 gx{"× did price change or fail"}:::gate s2 --> gx p00["send change alert"]:::task gx -->|"price changed"| p00 p10["send error alert"]:::task gx -->|"page unreadable"| p10 p00 --> s3 p10 --> s3 out[/"email sent on price change"/]:::out pay{{"catch competitor price moves early"}}:::pay s3 --> out out --> pay s2 -. "failures recorded, run continues" .-> out classDef task fill:#e7f6fe,stroke:#34b8f0,color:#2c2a29 classDef svc fill:#f6f8fa,stroke:#7c8795,color:#2c2a29 classDef mi fill:#e7f6fe,stroke:#0079a8,color:#2c2a29,stroke-width:2px classDef human fill:#fff,stroke:#0079a8,color:#0079a8 classDef store fill:#f6f8fa,stroke:#0079a8,color:#2c2a29 classDef trig fill:#00a4eb,stroke:#0079a8,color:#fff,font-weight:bold classDef trigtime fill:#00a4eb,stroke:#0079a8,color:#fff,font-weight:bold classDef trigdata fill:#8ad4f5,stroke:#0079a8,color:#06314c,font-weight:bold classDef gate fill:#fff,stroke:#e8a23d,color:#6b4708,font-weight:bold classDef out fill:#1f9d6b,stroke:#167a53,color:#fff,font-weight:bold classDef pay fill:#06314c,stroke:#021f33,color:#fff