package github

import (

"context"

"strconv"

)

// Metric names for the optional `fields` response-filtering feature. They let a

// dashboard answer two questions on real traffic: how often the model actually

// filters (adoption) and how many bytes that filtering removes (effectiveness).

//

// Cardinality is kept deliberately low: the only tags ever attached are `tool`

// (a small fixed set of tool names) and `filtered` (a boolean). Unbounded values

// such as repository, owner, user, the query, or the requested field list are

// never used as tags.

//

// The realized savings (bytes_full - bytes_sent) is intentionally not emitted as

// its own metric: it is derivable on the dashboard from the two byte counters,

// since sum(bytes_full) - sum(bytes_sent) equals the total saved at any rollup.

const (

metricFieldsToolCall = "mcp.fields.tool_call"

metricFieldsBytesFull = "mcp.fields.bytes_full"

metricFieldsBytesSent = "mcp.fields.bytes_sent"

)

// recordFieldsUsage emits telemetry for a single call to a tool that supports

// the `fields` parameter. It is best-effort: the local server wires a no-op

// metrics sink, while hosted deployments inject a real sink.

//

// Every call increments mcp.fields.tool_call tagged by tool and whether the

// response was filtered, which yields the adoption rate (filtered / total). When

// the response was filtered, it also records the unfiltered (fullBytes) and

// returned (sentBytes) payload sizes. Byte counters are only emitted for

// filtered calls so that "percent saved" (1 - bytes_sent / bytes_full) is

// computed over the population where filtering actually applied.

func recordFieldsUsage(ctx context.Context, deps ToolDependencies, tool string, filtered bool, fullBytes, sentBytes int) {

m := deps.Metrics(ctx)

if m == nil {

return

}

m.Increment(metricFieldsToolCall, map[string]string{

"tool": tool,

"filtered": strconv.FormatBool(filtered),

})

if !filtered {

return

}

toolTag := map[string]string{"tool": tool}

m.Counter(metricFieldsBytesFull, toolTag, int64(fullBytes))

m.Counter(metricFieldsBytesSent, toolTag, int64(sentBytes))

}