package weed_server

import (
	"strings"

	"github.com/seaweedfs/seaweedfs/weed/filer"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
)

// conditionIsSet reports whether a condition asks for any check at all.
func conditionIsSet(cond *filer_pb.WriteCondition) bool {
	return cond != nil && len(cond.Clauses) > 0
}

// writeConditionSatisfied reports whether the precondition holds against the
// current entry (nil if absent), evaluated under the path lock. Every clause
// must hold (logical AND).
func writeConditionSatisfied(cond *filer_pb.WriteCondition, current *filer.Entry) bool {
	for _, c := range cond.Clauses {
		if !clauseSatisfied(c, current) {
			return false
		}
	}
	return true
}

// clauseSatisfied evaluates one primitive against the current entry. For the
// ETag kinds, etags is a set: IF_ETAG_MATCH holds when the current ETag equals
// any member, IF_ETAG_NOT_MATCH when it equals none.
func clauseSatisfied(c *filer_pb.WriteCondition_Clause, current *filer.Entry) bool {
	exists := current != nil
	switch c.Kind {
	case filer_pb.WriteCondition_IF_NOT_EXISTS:
		return !exists
	case filer_pb.WriteCondition_IF_EXISTS:
		return exists
	case filer_pb.WriteCondition_IF_ETAG_MATCH:
		return exists && etagInSet(storedEntryETag(current), c.Etags, c.AllowWeak)
	case filer_pb.WriteCondition_IF_ETAG_NOT_MATCH:
		return !exists || !etagInSet(storedEntryETag(current), c.Etags, c.AllowWeak)
	case filer_pb.WriteCondition_IF_UNMODIFIED_SINCE:
		return !exists || current.Attr.Mtime.Unix() <= c.UnixTime
	case filer_pb.WriteCondition_IF_MODIFIED_SINCE:
		return !exists || current.Attr.Mtime.Unix() > c.UnixTime
	default:
		return true
	}
}

// etagInSet reports whether stored matches any candidate. A strong comparison
// (allowWeak false) treats a weak ETag as never equal; a weak comparison
// ignores the W/ marker on both sides.
func etagInSet(stored string, candidates []string, allowWeak bool) bool {
	for _, c := range candidates {
		if etagEqual(stored, c, allowWeak) {
			return true
		}
	}
	return false
}

func etagEqual(stored, expected string, allowWeak bool) bool {
	sv, sWeak := canonicalETag(stored)
	ev, eWeak := canonicalETag(expected)
	// RFC 7232 strong comparison: a weak ETag on either side never matches.
	if !allowWeak && (sWeak || eWeak) {
		return false
	}
	return sv == ev
}

// canonicalETag splits off the weak (W/) marker before stripping quotes, so a
// weak ETag like W/"abc" yields ("abc", true).
func canonicalETag(etag string) (value string, weak bool) {
	etag = strings.TrimSpace(etag)
	if strings.HasPrefix(etag, "W/") {
		return strings.Trim(etag[len("W/"):], `"`), true
	}
	return strings.Trim(etag, `"`), false
}

// storedEntryETag mirrors the S3 gateway's ETag precedence (the stored
// Seaweed ETag extended attribute, then the chunk/Md5 fallback) so conditional
// comparisons match what the gateway computes, without coupling the filer to
// S3 request handling.
func storedEntryETag(entry *filer.Entry) string {
	if v, ok := entry.Extended[s3_constants.ExtETagKey]; ok && len(v) > 0 {
		return normalizeETag(string(v))
	}
	return normalizeETag(filer.ETagEntry(entry))
}

func normalizeETag(etag string) string {
	return strings.Trim(etag, `"`)
}