package validator

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"strings"

	"browser.local/platform/domain"
)

const (
	MaxLogBatchEntries = 512
	MaxLogLineLength   = 8192
	MaxLogQueryLimit   = 10000
)

func ValidateLogBatchIngest(batch domain.LogBatchIngest) error {
	var violations []string
	violations = appendRequired(violations, "runEndpointId", batch.RunEndpointID)
	violations = appendRequired(violations, "sessionToken", batch.SessionToken)
	violations = appendRequired(violations, "logStreamId", batch.LogStreamID)
	violations = appendRequired(violations, "serverInstanceId", batch.ServerInstanceID)
	violations = appendRequired(violations, "streamKey", batch.StreamKey)
	violations = appendRequired(violations, "checksum", batch.Checksum)
	if !validLogStreamSource(batch.Source) {
		violations = append(violations, "source is invalid")
	}
	if batch.FirstSeq == 0 || batch.LastSeq == 0 {
		violations = append(violations, "sequence range must be positive")
	}
	if batch.FirstSeq > batch.LastSeq {
		violations = append(violations, "firstSeq must not exceed lastSeq")
	}
	if batch.Compression != "" && batch.Compression != "none" {
		violations = append(violations, "compression is invalid")
	}
	if len(batch.Entries) == 0 {
		violations = append(violations, "entries must not be empty")
	}
	if len(batch.Entries) > MaxLogBatchEntries {
		violations = append(violations, fmt.Sprintf("entries must not exceed %d", MaxLogBatchEntries))
	}
	if len(batch.Entries) > 0 {
		expectedCount := int(batch.LastSeq - batch.FirstSeq + 1)
		if expectedCount != len(batch.Entries) {
			violations = append(violations, "sequence range must match entry count")
		}
	}
	for i, entry := range batch.Entries {
		if entry.Seq != batch.FirstSeq+uint64(i) {
			violations = append(violations, fmt.Sprintf("entries[%d].seq must be contiguous", i))
		}
		if strings.TrimSpace(entry.Line) == "" {
			violations = append(violations, fmt.Sprintf("entries[%d].line is required", i))
		}
		if len(entry.Line) > MaxLogLineLength {
			violations = append(violations, fmt.Sprintf("entries[%d].line is too long", i))
		}
		for key := range entry.Fields {
			if strings.TrimSpace(key) == "" {
				violations = append(violations, fmt.Sprintf("entries[%d].fields key is required", i))
			}
		}
	}
	if batch.Checksum != "" {
		computed, err := LogEntriesChecksum(batch.Entries)
		if err != nil {
			violations = append(violations, "checksum cannot be computed")
		} else if batch.Checksum != computed && !logLineChecksumMatches(batch) {
			violations = append(violations, "checksum does not match entries")
		}
	}
	return finish(violations)
}

func ValidateLogStreamCursorQuery(query domain.LogStreamCursorQuery) error {
	var violations []string
	violations = appendRequired(violations, "logStreamId", query.LogStreamID)
	if query.Limit < 0 {
		violations = append(violations, "limit must not be negative")
	}
	if query.Limit > MaxLogQueryLimit {
		violations = append(violations, fmt.Sprintf("limit must not exceed %d", MaxLogQueryLimit))
	}
	return finish(violations)
}

func ValidateRunLogStreamProgress(request domain.RunLogStreamProgress) error {
	var violations []string
	violations = appendRequired(violations, "runEndpointId", request.RunEndpointID)
	violations = appendRequired(violations, "sessionToken", request.SessionToken)
	violations = appendRequired(violations, "serverInstanceId", request.ServerInstanceID)
	violations = appendRequired(violations, "logStreamId", request.LogStreamID)
	return finish(violations)
}

func LogEntriesChecksum(entries []domain.LogEntry) (string, error) {
	stable := make([]logEntryChecksumBody, len(entries))
	for i, entry := range entries {
		stable[i] = logEntryChecksumBody{
			Seq:       entry.Seq,
			Timestamp: entry.Timestamp.UTC().Format("2006-01-02T15:04:05.000000000Z07:00"),
			Level:     entry.Level,
			Line:      entry.Line,
			Fields:    entry.Fields,
			Redacted:  entry.Redacted,
		}
	}
	encoded, err := json.Marshal(stable)
	if err != nil {
		return "", err
	}
	sum := sha256.Sum256(encoded)
	return "sha256:" + hex.EncodeToString(sum[:]), nil
}

func logLineChecksumMatches(batch domain.LogBatchIngest) bool {
	if len(batch.Entries) != 1 {
		return false
	}
	return batch.Checksum == LogLineChecksum(batch.Entries[0].Line)
}

func LogLineChecksum(value string) string {
	sum := sha256.Sum256([]byte(value))
	return "sha256:" + hex.EncodeToString(sum[:])
}

type logEntryChecksumBody struct {
	Seq       uint64            `json:"seq"`
	Timestamp string            `json:"timestamp"`
	Level     string            `json:"level,omitempty"`
	Line      string            `json:"line"`
	Fields    map[string]string `json:"fields,omitempty"`
	Redacted  bool              `json:"redacted"`
}