mesh-controller/cmd/mesh-control/readable.go

package main

import (
	"encoding/json"
	"fmt"
	"time"

	"github.com/novox/mesh-control/internal/inventory"
)

// The same answers, in a shape something other than a person can read.
//
// A board reads through interfaces and holds nothing (novox/hq 03-DESIGN/01-to-be/11-a-board.md).
// Everything it needs is already answered by these commands — as text, for people, which is not
// something a page can read. So each of them can say it again as JSON.
//
// **`--json` rather than a serving API**, because nothing needs one yet: whatever serves a board
// runs the command, and the constraint in the design holds either way — the board never touches a
// context's store. An API is the larger thing and should wait until something is asking for it.
//
// **These shapes are hard to change once anything is built against them.** So they stay close to
// what the domain already calls things, and carry no summary field that would have to be kept
// true. Nothing here is derived that a reader could not derive.

// meshStatus is what `status --json` says: the three questions, in the order they are asked.
type meshStatus struct {
	// Wrong is every machine whose last declaration was refused or partly failed.
	Wrong []machineDoing `json:"wrong"`
	// Quiet is every machine not heard from lately. Not the same as wrong: new, switched off and
	// unreachable are not "tried and could not".
	Quiet []machineQuiet `json:"quiet"`
	// Behind is every module built from something older than its source has.
	Behind []moduleBehind `json:"behind"`
	// Machines is how many the mesh knows about, so a reader can tell "none wrong" from
	// "none at all".
	Machines int `json:"machines"`
}

type machineDoing struct {
	Node string `json:"node"`
	// Outcome is refused or failed. Kept distinct all the way out: they are fixed in different
	// places, and one word for both sends half the readers to the wrong one.
	Outcome string `json:"outcome"`
	Refused string `json:"refused,omitempty"`
	Failed  []struct {
		ID    string `json:"id"`
		Error string `json:"error"`
	} `json:"failed,omitempty"`
	Applied int       `json:"applied"`
	At      time.Time `json:"at"`
}

type machineQuiet struct {
	Node string `json:"node"`
	// LastSeen is absent when the machine has never spoken, which is a different thing from
	// having been quiet for a while.
	LastSeen *time.Time `json:"lastSeen,omitempty"`
}

type moduleBehind struct {
	Module    string   `json:"module"`
	BuiltFrom string   `json:"builtFrom"`
	Head      string   `json:"head"`
	On        []string `json:"on"`
}

// statusAsJSON answers the same three questions as the text form, from the same calls.
func statusAsJSON(wrong []inventory.Doing, nodes []inventory.Node, quiet []inventory.Node,
	behind map[string][]string, sources map[string]inventory.Source) ([]byte, error) {

	out := meshStatus{Machines: len(nodes), Wrong: []machineDoing{},
		Quiet: []machineQuiet{}, Behind: []moduleBehind{}}

	for _, d := range wrong {
		row := machineDoing{
			Node: d.Node, Outcome: d.Outcome, Refused: d.Refused, Applied: d.Applied, At: d.At,
		}
		for _, f := range d.Failed {
			row.Failed = append(row.Failed, struct {
				ID    string `json:"id"`
				Error string `json:"error"`
			}{ID: f.ID, Error: f.Error})
		}
		out.Wrong = append(out.Wrong, row)
	}
	for _, n := range quiet {
		row := machineQuiet{Node: n.Name}
		if !n.LastSeen.IsZero() {
			seen := n.LastSeen
			row.LastSeen = &seen
		}
		out.Quiet = append(out.Quiet, row)
	}
	for module, on := range behind {
		from := sources[module]
		out.Behind = append(out.Behind, moduleBehind{
			Module: module, BuiltFrom: from.BuiltFrom, Head: from.Head, On: on,
		})
	}
	return json.MarshalIndent(out, "", "  ")
}

// say prints a value as JSON, for the commands that can answer either way.
func say(value any) error {
	body, err := json.MarshalIndent(value, "", "  ")
	if err != nil {
		return err
	}
	fmt.Println(string(body))
	return nil
}