// Package legal is the "Legal Sentinel" — license compliance & policy
// enforcement for the Coven.
//
// It acts as a Pre-Forge Filter: every cast request is intercepted and
// compared against the active Compliance Profile. Three templates ship
// out-of-the-box:
//
//   strict_copyleft   — FSF/GNU style, blocks all proprietary blobs
//   corporate_lite    — MIT/Apache friendly, AGPL/SSPL blacklisted
//   lawless           — "for the brave", silent audit only
//
// The package also generates SBOM exports (SPDX / CycloneDX) so the legal
// department can audit the fleet from a single command.
package legal

import (
	"fmt"
	"strings"
)

// Policy is the active posture of the Coven.
type Policy struct {
	Name                  string
	AllowedFamilies       []string
	Blacklist             []string
	FailOnProprietary     bool
	FailOnCopyleftViral   bool
	AllowInternalProprietary bool
	RequireAttribution    bool
	SilentMode            bool // lawless — log only, never block
	AutoAcceptEULA        bool
}

// LicenseInfo is what the Grimoire parser yields up about a spell.
type LicenseInfo struct {
	SpellName   string
	License     string
	IsCopyleft  bool
	IsProprietary bool
	Internal    bool
}

// Sentinel is the engine that validates casts.
type Sentinel struct {
	Policy Policy
}

// Validate runs the policy against a spell's license. Returns an error if
// the cast must be blocked; nil if it's allowed (possibly with a warning
// stored in `warnings`).
func (s *Sentinel) Validate(info LicenseInfo) (warnings []string, err error) {
	// Lawless — never blocks.
	if s.Policy.SilentMode {
		return nil, nil
	}
	// 1. Blacklist check.
	for _, b := range s.Policy.Blacklist {
		if strings.EqualFold(info.License, b) {
			return nil, fmt.Errorf("legal: license %s is blacklisted by policy %q", info.License, s.Policy.Name)
		}
	}
	// 2. Proprietary check.
	if info.IsProprietary && s.Policy.FailOnProprietary {
		if info.Internal && s.Policy.AllowInternalProprietary {
			warnings = append(warnings, "internal proprietary spell — verify deployment target")
			return warnings, nil
		}
		return nil, fmt.Errorf("legal: proprietary licenses blocked by policy %q", s.Policy.Name)
	}
	// 3. Viral copyleft check.
	if info.IsCopyleft && s.Policy.FailOnCopyleftViral {
		return nil, fmt.Errorf("legal: viral copyleft (%s) blocked by policy %q", info.License, s.Policy.Name)
	}
	// 4. Allowed families.
	if len(s.Policy.AllowedFamilies) > 0 && !contains(s.Policy.AllowedFamilies, familyOf(info.License)) {
		if s.Policy.SilentMode {
			warnings = append(warnings, fmt.Sprintf("license %s outside allowed families", info.License))
			return warnings, nil
		}
		return nil, fmt.Errorf("legal: license %s not in allowed families %v", info.License, s.Policy.AllowedFamilies)
	}
	if info.IsCopyleft {
		warnings = append(warnings, "copyleft spell — audit required for proprietary Essence integration")
	}
	return warnings, nil
}

// familyOf reduces a specific license string ("GPL-3.0-only") to its family
// ("GPL") so the policy can be expressed at family granularity.
func familyOf(license string) string {
	license = strings.ToUpper(strings.TrimSpace(license))
	for _, fam := range []string{"GPL", "LGPL", "AGPL", "MIT", "BSD", "APACHE", "ISC", "MPL", "SSPL", "WTFPL", "UNLICENSE"} {
		if strings.HasPrefix(license, fam) {
			return fam
		}
	}
	return license
}

func contains(haystack []string, needle string) bool {
	for _, h := range haystack {
		if strings.EqualFold(h, needle) {
			return true
		}
	}
	return false
}

// StrictCopyleft is the FSF/GNU posture.
func StrictCopyleft() Policy {
	return Policy{
		Name:                  "strict_copyleft",
		AllowedFamilies:       []string{"GPL", "LGPL", "MIT", "BSD", "APACHE", "ISC", "MPL", "UNLICENSE"},
		Blacklist:             []string{"CC-BY-NC-ND", "SSPL", "WTFPL"},
		FailOnProprietary:     true,
		RequireAttribution:    true,
	}
}

// CorporateLite is the MIT/Apache-friendly posture.
func CorporateLite() Policy {
	return Policy{
		Name:                  "corporate_lite",
		AllowedFamilies:       []string{"MIT", "BSD", "APACHE", "ISC", "UNLICENSE"},
		Blacklist:             []string{"AGPL", "SSPL"},
		FailOnCopyleftViral:   true,
		AllowInternalProprietary: true,
	}
}

// Lawless is the "for the brave" posture — never blocks, only audits.
func Lawless() Policy {
	return Policy{
		Name:           "lawless",
		SilentMode:     true,
		AutoAcceptEULA: true,
	}
}

// LoadPolicy returns the matching Policy object for a profile name.
func LoadPolicy(name string) (Policy, error) {
	switch name {
	case "strict_copyleft":
		return StrictCopyleft(), nil
	case "corporate_lite":
		return CorporateLite(), nil
	case "lawless":
		return Lawless(), nil
	}
	return Policy{}, fmt.Errorf("legal: unknown profile %q", name)
}