FIT File CLI (processFitFile)

Small CLI to process a .fit activity file and print a compact JSON summary.

Purpose

This binary was extracted from an AWS Lambda function. It decodes a FIT file, extracts activity records, runs the existing analysis logic, and prints a JSON object with only the fields you care about.

The CLI prints the following JSON fields:

• HeartAnalysis (map / zone buckets)
• ElevationGain (float)
• StoppedTime (seconds)
• ElapsedTime (seconds)
• NormalizedPower (float)
• PowerAnalysis (map / zone buckets) The CLI may also include these additional fields when available:
• SimplifiedCoordinates (array of [lon, lat, elevation] points)
• SimplifiedDistances (array of distances aligned with simplified coordinates)
• SimplifiedElevations (array of elevations aligned with simplified coordinates)

Prerequisites

• Go 1.20+ (module-aware). Ensure go is on your PATH.
• Run commands from the src directory (this repository's CLI package lives here).

Build

To build a local binary:

cd /path/to/.../processFitFile/src
go build -o processFitFile

Run (development)

You can run without building:

# run against the included fixture
go run . --fit fixtures/Morning_Ride-8.fit

# or with a built binary
./processFitFile --fit fixtures/Morning_Ride-8.fit

Testing

Run all tests across the module (root and subpackages):

go test ./...

Verbose output:

go test -v ./...

Run a single test (by name pattern):

go test -run TestName ./...

Run tests in a specific package (from repo root):

go test -v .            # root package
go test -v ./fitHelper  # example subpackage

With race detector:

go test -race ./...

Coverage summary and HTML report:

go test -coverprofile=coverage.out ./...
go tool cover -func=coverage.out
go tool cover -html=coverage.out

Notes:

• Ensure Go is installed and your working directory is the repository root.
• Some tests may read from fixtures/ or testdata/; paths are relative to the package under test.

Example output

The program prints a single JSON object to stdout. Example (trimmed):

{
  "HeartAnalysis": { "1": 255, "10": 255, ... },
  "ElevationGain": 0,
  "StoppedTime": 15899,
  "ElapsedTime": 35276,
  "NormalizedPower": 183.89182,
  "PowerAnalysis": { "1": 738, "10": 607, ... }
}

If the CLI includes the optional simplified timeseries, the output can also contain:

"SimplifiedCoordinates": [[-122.4, 45.5, 123.4], [-122.401, 45.501, 124.3], ...],
"SimplifiedDistances": [0, 12.3, 24.6, ...],
"SimplifiedElevations": [123.4, 124.3, 125.0, ...]

How it works (brief)

• main.go is the CLI entry. It reads the .fit file, calls ProcessActivityRecords, and prints the requested JSON fields.
• process.go contains the activity processing logic (power, cadence, simplification, etc.).
• fitHelper decodes the FIT file and returns a fit.ActivityFile.
• The program reuses existing dynamo types for the shape of analysis results.

Notes and next steps

• Units: Elevation/Distance conversions follow the original code. If you want different units, we can change conversions in process.go.
• Output file: I can add a --out <file> flag to write the JSON to disk.
• Tests: Add small unit tests for ProcessActivityRecords to guard behavior on small fixture files.

JSON Schema (validation)

You can validate the CLI output against the included JSON Schema. A schema is available at src/output.schema.json and matches the fields printed by the CLI (including the optional simplified arrays).

Example validation with ajv (recommended):

# install ajv-cli if you don't have it
npm install -g ajv-cli

# validate output.json against schema
ajv validate -s output.schema.json -d output.json --strict=false

The schema is also embedded below for quick reference.

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "HeartAnalysis": { "type": "object", "additionalProperties": { "type": "integer" } },
    "PowerAnalysis": { "type": "object", "additionalProperties": { "type": "integer" } },
    "ElevationGain": { "type": "number" },
    "StoppedTime": { "type": "integer" },
    "ElapsedTime": { "type": "integer" },
    "NormalizedPower": { "type": "number" },
    "SimplifiedCoordinates": {
      "type": "array",
      "items": { "type": "array", "minItems": 3, "maxItems": 3, "items": { "type": "number" } }
    },
    "SimplifiedDistances": { "type": "array", "items": { "type": "number" } },
    "SimplifiedElevations": { "type": "array", "items": { "type": "number" } }
  },
  "required": ["HeartAnalysis","PowerAnalysis","ElevationGain","StoppedTime","ElapsedTime","NormalizedPower"]
}

If you want any changes to the JSON shape or extra CLI flags, tell me which fields or flags and I will add them.