<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;
use Illuminate\Database\Eloquent\Relations\HasMany;

class DocumentChunk extends Model
{
    // =========================================================================
    // STATUS CONSTANTS
    // =========================================================================

    /** Baru dicipta, belum di-embed */
    const STATUS_PENDING = 'pending';

    /** Berjaya di-embed, aktif dalam Qdrant */
    const STATUS_INDEXED = 'indexed';

    /** Ditandakan untuk semak admin, masih aktif dalam Qdrant */
    const STATUS_NEEDS_REVIEW = 'needs_review';

    /** final_text ditukar, perlu embed semula */
    const STATUS_NEEDS_REINDEX = 'needs_reindex';

    /** Admin kecualikan — is_active=false dalam Qdrant */
    const STATUS_EXCLUDED = 'excluded';

    /** Chunk asal selepas split — digantikan oleh child chunks */
    const STATUS_SUPERSEDED = 'superseded';

    /** Embedding gagal selepas semua retry */
    const STATUS_FAILED_EMBEDDING = 'failed_embedding';

    // =========================================================================
    // MODEL DEFINITION
    // =========================================================================

    protected $fillable = [
        'document_id',
        'document_version_id',
        'chunk_index',
        'page_number',
        'content',           // raw_text asal — TIDAK PERNAH DIUBAH
        'cleaned_text',      // auto-cleaned version (optional)
        'final_text',        // teks akhir untuk embedding (admin-edited)
        'token_count',
        'section_heading',
        'qdrant_point_id',
        'is_embedded',
        'is_active',
        'embedded_at',
        'chunk_status',
        'is_edited',
        'exclude_from_index',
        'needs_reindex',
        'parent_chunk_id',
        'split_group_id',
        'split_order',
        'edited_by',
        'edited_at',
        'last_embedded_at',
        'notes',
    ];

    protected $casts = [
        'is_embedded'        => 'boolean',
        'is_active'          => 'boolean',
        'is_edited'          => 'boolean',
        'exclude_from_index' => 'boolean',
        'needs_reindex'      => 'boolean',
        'embedded_at'        => 'datetime',
        'edited_at'          => 'datetime',
        'last_embedded_at'   => 'datetime',
    ];

    // =========================================================================
    // RELATIONSHIPS
    // =========================================================================

    public function document(): BelongsTo
    {
        return $this->belongsTo(Document::class);
    }

    public function documentVersion(): BelongsTo
    {
        return $this->belongsTo(DocumentVersion::class);
    }

    /** Chunk asal jika ini adalah hasil split */
    public function parentChunk(): BelongsTo
    {
        return $this->belongsTo(DocumentChunk::class, 'parent_chunk_id');
    }

    /** Child chunks jika chunk ini pernah di-split */
    public function childChunks(): HasMany
    {
        return $this->hasMany(DocumentChunk::class, 'parent_chunk_id')
            ->orderBy('split_order');
    }

    /** Admin yang terakhir edit chunk ini */
    public function editor(): BelongsTo
    {
        return $this->belongsTo(User::class, 'edited_by');
    }

    /** Audit trail khusus chunk ini */
    public function audits(): HasMany
    {
        return $this->hasMany(ChunkAudit::class, 'document_chunk_id')
            ->latest('created_at');
    }

    // =========================================================================
    // QUERY SCOPES
    // =========================================================================

    public function scopeActive(Builder $query): Builder
    {
        return $query->where('is_active', true);
    }

    public function scopeEmbedded(Builder $query): Builder
    {
        return $query->where('is_embedded', true);
    }

    public function scopeNotEmbedded(Builder $query): Builder
    {
        return $query->where('is_embedded', false);
    }

    public function scopeForVersion(Builder $query, int $versionId): Builder
    {
        return $query->where('document_version_id', $versionId);
    }

    /**
     * Chunk yang layak untuk indexing (digunakan oleh chatbot).
     * Tidak termasuk: excluded, superseded, failed_embedding.
     */
    public function scopeIndexable(Builder $query): Builder
    {
        return $query
            ->where('is_active', true)
            ->where('exclude_from_index', false)
            ->whereNotIn('chunk_status', [
                self::STATUS_EXCLUDED,
                self::STATUS_SUPERSEDED,
                self::STATUS_FAILED_EMBEDDING,
            ]);
    }

    public function scopeNeedsReindex(Builder $query): Builder
    {
        return $query->where('needs_reindex', true);
    }

    public function scopeByStatus(Builder $query, string $status): Builder
    {
        return $query->where('chunk_status', $status);
    }

    /** Hanya chunk asal (bukan hasil split) */
    public function scopeTopLevel(Builder $query): Builder
    {
        return $query->whereNull('parent_chunk_id');
    }

    // =========================================================================
    // TEXT HELPERS
    // =========================================================================

    /**
     * Teks yang digunakan untuk embedding.
     * Priority: final_text > cleaned_text > content
     *
     * Ini adalah SATU-SATUNYA method yang perlu digunakan untuk embedding.
     */
    public function getEmbeddableText(): string
    {
        return $this->final_text
            ?? $this->cleaned_text
            ?? $this->content;
    }

    /**
     * raw_text = alias untuk content (teks asal extraction).
     * Digunakan dalam views untuk kejelasan.
     */
    public function getRawTextAttribute(): string
    {
        return $this->content;
    }

    /**
     * Bina Qdrant payload untuk chunk ini.
     * Panggil selepas eager load: document.category, documentVersion.
     */
    public function toQdrantPayload(): array
    {
        $document = $this->document;
        $version  = $this->documentVersion;
        $category = $document->category;

        return [
            'knowledge_type'      => 'pdf_chunk',
            'source_type'         => 'pdf',
            'category_id'         => $category->id,
            'category_name'       => $category->name,
            'category_slug'       => $category->slug,
            'document_id'         => $document->id,
            'document_version_id' => $version->id,
            'document_chunk_id'   => $this->id,
            'knowledge_item_id'   => null,
            'title'               => $document->title,
            'page_number'         => $this->page_number,
            'chunk_index'         => $this->chunk_index,
            'section_heading'     => $this->section_heading,
            'text'                => mb_substr($this->getEmbeddableText(), 0, 1000),
            'is_active'           => true,
            'status'              => 'active',
            'is_edited'           => (bool) $this->is_edited,
            'tags'                => $document->tags ?? [],
            'effective_date'      => $document->effective_date?->toDateString(),
            'language'            => $document->language,
            'created_at'          => now()->toIso8601String(),
        ];
    }

    // =========================================================================
    // STATE MUTATORS
    // =========================================================================

    /**
     * Deactivate chunk — digunakan bila versi baru diupload.
     */
    public function deactivate(): void
    {
        $this->update(['is_active' => false]);
    }

    /**
     * Tandakan chunk berjaya di-embed.
     * Dipanggil selepas upsert ke Qdrant berjaya.
     */
    public function markAsEmbedded(string $qdrantPointId): void
    {
        $this->update([
            'qdrant_point_id'  => $qdrantPointId,
            'is_embedded'      => true,
            'embedded_at'      => $this->embedded_at ?? now(), // kekalkan masa embed pertama
            'last_embedded_at' => now(),
            'chunk_status'     => self::STATUS_INDEXED,
            'needs_reindex'    => false,
        ]);
    }

    /**
     * Tandakan chunk sebagai superseded (selepas split).
     */
    public function markAsSuperseded(): void
    {
        $this->update([
            'is_active'          => false,
            'exclude_from_index' => true,
            'chunk_status'       => self::STATUS_SUPERSEDED,
        ]);
    }

    /**
     * Tandakan chunk sebagai excluded (admin kecualikan).
     */
    public function markAsExcluded(): void
    {
        $this->update([
            'is_active'          => false,
            'exclude_from_index' => true,
            'chunk_status'       => self::STATUS_EXCLUDED,
        ]);
    }

    /**
     * Kembalikan chunk ke indexing selepas excluded.
     */
    public function markAsIncluded(): void
    {
        $status = $this->is_embedded
            ? self::STATUS_INDEXED
            : self::STATUS_NEEDS_REINDEX;

        $this->update([
            'is_active'          => true,
            'exclude_from_index' => false,
            'chunk_status'       => $status,
            'needs_reindex'      => !$this->is_embedded,
        ]);
    }

    // =========================================================================
    // STATUS HELPERS (untuk views)
    // =========================================================================

    public function isIndexable(): bool
    {
        return $this->is_active
            && ! $this->exclude_from_index
            && ! in_array($this->chunk_status, [
                self::STATUS_EXCLUDED,
                self::STATUS_SUPERSEDED,
                self::STATUS_FAILED_EMBEDDING,
            ]);
    }

    public function isSuperseded(): bool
    {
        return $this->chunk_status === self::STATUS_SUPERSEDED;
    }

    public function getStatusBadgeClass(): string
    {
        return match ($this->chunk_status) {
            self::STATUS_INDEXED          => 'bg-success',
            self::STATUS_NEEDS_REINDEX    => 'bg-warning text-dark',
            self::STATUS_NEEDS_REVIEW     => 'bg-info text-dark',
            self::STATUS_EXCLUDED         => 'bg-secondary',
            self::STATUS_SUPERSEDED       => 'bg-dark',
            self::STATUS_FAILED_EMBEDDING => 'bg-danger',
            default                       => 'bg-light text-dark border',
        };
    }

    public function getStatusLabel(): string
    {
        return match ($this->chunk_status) {
            self::STATUS_PENDING          => 'Menunggu',
            self::STATUS_INDEXED          => 'Diindex',
            self::STATUS_NEEDS_REVIEW     => 'Perlu Semak',
            self::STATUS_NEEDS_REINDEX    => 'Perlu Reindex',
            self::STATUS_EXCLUDED         => 'Dikecualikan',
            self::STATUS_SUPERSEDED       => 'Digantikan',
            self::STATUS_FAILED_EMBEDDING => 'Gagal Embed',
            default                       => ucfirst($this->chunk_status),
        };
    }

    /** Anggaran token berdasarkan teks yang akan di-embed */
    public function estimateTokenCount(): int
    {
        return (int) ceil(mb_strlen($this->getEmbeddableText()) / 4);
    }
}