package main

// The container runtime's log rotation, checked before it reaches daemon.json (novox/hq issue 452).
//
// **Why a step and not the file alone.** daemon.json's log-driver and log-opts are filled by the controller
// from this module's settings log-max-size and log-max-file, pasted as text (novox/hq issue 346): the
// controller judges nothing but that a value is one line. The runtime is the only reader of daemon.json and
// reads log-opts only when it starts, so a bad value would be found at the runtime's next start, as a runtime
// that does not start, and a value with a quote in it could add any key to the file. So the module's
// manifest writes the same two values into log-rotation.conf first, and runs this as a step before daemon.json:
// a value refused here fails the step, and the host skips the rest of the module (novox/hq ADR 0136), so
// daemon.json keeps what it had, and the refusal is in the apply's report.

import (
	"fmt"
	"os"
	"regexp"
	"strings"
)

// logRotation is what log-rotation.conf says, both values as the runtime takes them: text.
type logRotation struct{ Size, Files string }

var (
	// A size as the json-file driver reads it, with the unit required and in lower case, as decided on issue
	// 452: a whole number from 1 with k, m or g, at most nine digits, so no value overflows the runtime's count.
	logSize = regexp.MustCompile(`^[1-9][0-9]{0,8}[kmg]$`)
	// A count of files from 1 to 99, without a leading zero.
	logFiles = regexp.MustCompile(`^[1-9][0-9]?$`)
)

// parseLogRotation reads `size=` and `files=` once each; a comment or an empty line is skipped, and any other
// line is refused, so a value that brought a line of its own is never read past.
func parseLogRotation(text string) (logRotation, error) {
	var got logRotation
	seen := map[string]bool{}
	for _, line := range strings.Split(text, "\n") {
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		key, value, ok := strings.Cut(line, "=")
		if !ok || (key != "size" && key != "files") {
			return logRotation{}, fmt.Errorf("log-rotation.conf has a line that is not size= or files=: %q", line)
		}
		if seen[key] {
			return logRotation{}, fmt.Errorf("log-rotation.conf says %s twice", key)
		}
		seen[key] = true
		switch key {
		case "size":
			if !logSize.MatchString(value) {
				return logRotation{}, fmt.Errorf("log-max-size %q is not a size: a whole number from 1 with k, m or g "+
					"after it, such as 100m; daemon.json was left as it is", value)
			}
			got.Size = value
		case "files":
			if !logFiles.MatchString(value) {
				return logRotation{}, fmt.Errorf("log-max-file %q is not a count from 1 to 99; daemon.json was left "+
					"as it is", value)
			}
			got.Files = value
		}
	}
	for _, key := range []string{"size", "files"} {
		if !seen[key] {
			return logRotation{}, fmt.Errorf("log-rotation.conf does not say %s", key)
		}
	}
	return got, nil
}

// checkLogRotationFile is the step: the file the manifest wrote, judged.
func checkLogRotationFile(path string) error {
	raw, err := os.ReadFile(path)
	if err != nil {
		return err
	}
	_, err = parseLogRotation(string(raw))
	return err
}