package buildstep

import (
	"encoding/json"
	"os"

	"git.novox.be/novox/mesh-sdk/go/buildcpu"
)

// NodeLimits is what one step on node is held to (novox/hq issue 1806): the node's processor cap from the module's
// settings file at path (buildcpu.Setting, its default when the file does not set it), the machine's processors, and
// the node's capacity, so the steps that run at once start no more threads together than the cap gives. Read at every
// call, like the capacity, so a change takes effect at the next step. A file or a setting that cannot be read gives the
// default cap and says why: a step still runs with a bound, never without one.
func NodeLimits(path, node string, slots int, logf func(string, ...any)) buildcpu.Limits {
	setting := buildcpu.Defaults
	if path != "" {
		if raw, err := os.ReadFile(path); err != nil {
			sayTo(logf, "the processor cap cannot be read, so %s builds under the default cap: %v", node, err)
		} else {
			var s map[string]any
			if err := json.Unmarshal(raw, &s); err != nil {
				sayTo(logf, "the settings file %s is not JSON, so %s builds under the default cap: %v", path, node, err)
			} else if v, ok := s[buildcpu.Setting].(string); ok {
				setting = v
			}
		}
	}
	l, err := buildcpu.LimitsFor(setting, node, slots)
	if err != nil {
		sayTo(logf, "%v, so %s builds under the default cap of %d%%", err, node, buildcpu.DefaultPercent)
	}
	return l
}

func sayTo(logf func(string, ...any), format string, args ...any) {
	if logf != nil {
		logf(format, args...)
	}
}