package agent

import (
	"fmt"
	"regexp"
	"strconv"
)

// MinVersions defines the minimum required CLI version for each agent type.
// Versions below these will be rejected during daemon registration.
var MinVersions = map[string]string{
	"claude": "2.0.0",
	"codex":  "0.100.0", // app-server --listen stdio:// added in 0.100.0
}

// semver holds a parsed semantic version (major.minor.patch).
type semver struct {
	Major, Minor, Patch int
}

// versionRe matches version strings like "2.1.100", "v2.0.0", or
// "2.1.100 (Claude Code)" — it extracts the first three numeric components.
var versionRe = regexp.MustCompile(`v?(\d+)\.(\d+)\.(\d+)`)

// parseSemver extracts a semver from a version string.
func parseSemver(raw string) (semver, error) {
	m := versionRe.FindStringSubmatch(raw)
	if m == nil {
		return semver{}, fmt.Errorf("cannot parse version %q", raw)
	}
	major, _ := strconv.Atoi(m[1])
	minor, _ := strconv.Atoi(m[2])
	patch, _ := strconv.Atoi(m[3])
	return semver{Major: major, Minor: minor, Patch: patch}, nil
}

// lessThan returns true if v < other.
func (v semver) lessThan(other semver) bool {
	if v.Major != other.Major {
		return v.Major < other.Major
	}
	if v.Minor != other.Minor {
		return v.Minor < other.Minor
	}
	return v.Patch < other.Patch
}

// CheckMinVersion validates that detectedVersion meets the minimum for agentType.
// Returns nil if the version is acceptable or no minimum is defined.
func CheckMinVersion(agentType, detectedVersion string) error {
	minRaw, ok := MinVersions[agentType]
	if !ok {
		return nil
	}
	min, err := parseSemver(minRaw)
	if err != nil {
		return fmt.Errorf("invalid minimum version %q for %s: %w", minRaw, agentType, err)
	}
	detected, err := parseSemver(detectedVersion)
	if err != nil {
		return fmt.Errorf("cannot parse detected %s version %q: %w", agentType, detectedVersion, err)
	}
	if detected.lessThan(min) {
		return fmt.Errorf("%s version %s is below minimum required %s — please upgrade", agentType, detectedVersion, minRaw)
	}
	return nil
}