<?php

namespace Leantime\Core\WorkStructure\Services;

use Leantime\Core\Events\DispatchesEvents;
use Leantime\Core\WorkStructure\Models\WorkStructure;
use Leantime\Core\WorkStructure\Repositories\WorkStructureRepository;

/**
 * Cross-structure mapping query service.
 *
 * Resolves element type mappings between different work structures
 * (e.g., Logic Model "output" → Project "milestone").
 *
 * @api
 */
class MappingService
{
    use DispatchesEvents;

    /**
     * @param  WorkStructureRepository  $repo  WorkStructure repository
     */
    public function __construct(
        private WorkStructureRepository $repo
    ) {}

    /**
     * Get all mappings between two structures.
     *
     * @param  int  $sourceStructureId  Source structure ID
     * @param  int  $targetStructureId  Target structure ID
     * @return \Leantime\Core\WorkStructure\Models\StructureMapping[]
     *
     * @api
     */
    public function getMappings(int $sourceStructureId, int $targetStructureId): array
    {
        return $this->repo->getMappings($sourceStructureId, $targetStructureId);
    }

    /**
     * Get the target element type key for a given source element type key.
     *
     * @param  int  $sourceStructureId  Source structure ID
     * @param  string  $sourceTypeKey  Source element type key
     * @param  int  $targetStructureId  Target structure ID
     * @return string|null Target element type key, or null if no mapping exists
     *
     * @api
     */
    public function getTargetElementKey(int $sourceStructureId, string $sourceTypeKey, int $targetStructureId): ?string
    {
        $sourceElement = $this->repo->getElementByTypeKey($sourceStructureId, $sourceTypeKey);

        if ($sourceElement === null) {
            return null;
        }

        $mappings = $this->repo->getMappings($sourceStructureId, $targetStructureId);

        // Resolve target element IDs → typeKeys with a single fetch instead of
        // re-querying all target elements inside the mappings loop.
        $targetIdToKey = [];
        foreach ($this->repo->getElements($targetStructureId) as $el) {
            $targetIdToKey[$el->id] = $el->typeKey;
        }

        foreach ($mappings as $mapping) {
            if ($mapping->sourceElementId === $sourceElement->id) {
                return $targetIdToKey[$mapping->targetElementId] ?? null;
            }
        }

        return null;
    }

    /**
     * Get all target structures that have mappings from a given source structure.
     *
     * Each returned structure includes its elements populated.
     *
     * @param  int  $sourceStructureId  Source structure ID
     * @return WorkStructure[]
     *
     * @api
     */
    public function getTargetStructures(int $sourceStructureId): array
    {
        $targetIds = $this->repo->getTargetStructureIds($sourceStructureId);
        $structures = [];

        foreach ($targetIds as $targetId) {
            $structure = $this->repo->getStructure($targetId);

            if ($structure !== null) {
                $structure->elements = $this->repo->getElements($targetId);
                $structures[] = $structure;
            }
        }

        return $structures;
    }

    /**
     * Get target element type keys that have mappings from the source structure.
     *
     * @param  int  $sourceStructureId  Source structure ID
     * @param  int  $targetStructureId  Target structure ID
     * @return string[] Array of target element typeKeys (e.g., ['milestone', 'task', 'goal'])
     *
     * @api
     */
    public function getMappedElementKeys(int $sourceStructureId, int $targetStructureId): array
    {
        $mappings = $this->repo->getMappings($sourceStructureId, $targetStructureId);
        $targetElements = $this->repo->getElements($targetStructureId);

        $elementIdToKey = [];
        foreach ($targetElements as $el) {
            $elementIdToKey[$el->id] = $el->typeKey;
        }

        $keys = [];
        foreach ($mappings as $mapping) {
            $key = $elementIdToKey[$mapping->targetElementId] ?? null;
            if ($key !== null && ! in_array($key, $keys, true)) {
                $keys[] = $key;
            }
        }

        return $keys;
    }

    /**
     * Get the source element type key for a given target element type key.
     *
     * @param  int  $targetStructureId  Target structure ID
     * @param  string  $targetTypeKey  Target element type key
     * @param  int  $sourceStructureId  Source structure ID
     * @return string|null Source element type key, or null if no mapping exists
     *
     * @api
     */
    public function getSourceElementKey(int $targetStructureId, string $targetTypeKey, int $sourceStructureId): ?string
    {
        $targetElement = $this->repo->getElementByTypeKey($targetStructureId, $targetTypeKey);

        if ($targetElement === null) {
            return null;
        }

        $mappings = $this->repo->getMappings($sourceStructureId, $targetStructureId);

        // Resolve source element IDs → typeKeys with a single fetch instead of
        // re-querying all source elements inside the mappings loop.
        $sourceIdToKey = [];
        foreach ($this->repo->getElements($sourceStructureId) as $el) {
            $sourceIdToKey[$el->id] = $el->typeKey;
        }

        foreach ($mappings as $mapping) {
            if ($mapping->targetElementId === $targetElement->id) {
                return $sourceIdToKey[$mapping->sourceElementId] ?? null;
            }
        }

        return null;
    }
}