<?php

namespace App\Services;

use CodeIgniter\Database\BaseConnection;

final class StudentScoreHistoryService
{
    public function __construct(private readonly BaseConnection $db)
    {
    }

    /**
     * Build one score-history row per student and school year.
     *
     * @return array<int, array<int, array<string, mixed>>>
     */
    public function forStudents(array $studentIds): array
    {
        $studentIds = array_values(array_unique(array_filter(
            array_map('intval', $studentIds),
            static fn(int $id): bool => $id > 0
        )));
        if ($studentIds === []) {
            return [];
        }

        $history = [];
        $semesterRows = $this->latestSemesterRows($studentIds);
        foreach ($semesterRows as $row) {
            $studentId = (int) ($row['student_id'] ?? 0);
            $schoolYear = trim((string) ($row['school_year'] ?? ''));
            $semester = $this->normalizeSemester($row['semester'] ?? '');
            if ($studentId <= 0 || $schoolYear === '' || !in_array($semester, ['fall', 'spring'], true)) {
                continue;
            }

            $history[$studentId][$schoolYear] ??= $this->emptyYear($schoolYear);
            if ($semester === 'fall') {
                $history[$studentId][$schoolYear]['midterm_s1'] = $this->score($row['midterm_exam_score'] ?? null);
                $history[$studentId][$schoolYear]['ptap_s1'] = $this->score($row['ptap_score'] ?? null);
                $history[$studentId][$schoolYear]['attendance_s1'] = $this->score($row['attendance_score'] ?? null);
                $history[$studentId][$schoolYear]['_semester_score_s1'] = $this->score($row['semester_score'] ?? null);
            } else {
                $finalScore = $this->score($row['final_exam_score'] ?? null);
                if ($finalScore === null) {
                    // Some older Spring rows stored the final in this legacy column.
                    $finalScore = $this->score($row['midterm_exam_score'] ?? null);
                }
                $history[$studentId][$schoolYear]['final_s2'] = $finalScore;
                $history[$studentId][$schoolYear]['ptap_s2'] = $this->score($row['ptap_score'] ?? null);
                $history[$studentId][$schoolYear]['attendance_s2'] = $this->score($row['attendance_score'] ?? null);
                $history[$studentId][$schoolYear]['_semester_score_s2'] = $this->score($row['semester_score'] ?? null);
            }
        }

        foreach ($this->commentRows($studentIds) as $row) {
            $studentId = (int) ($row['student_id'] ?? 0);
            $schoolYear = trim((string) ($row['school_year'] ?? ''));
            $semester = $this->normalizeSemester($row['semester'] ?? '');
            $type = $this->normalizeCommentType($row['score_type'] ?? '');
            if ($studentId <= 0 || $schoolYear === '') {
                continue;
            }

            $history[$studentId][$schoolYear] ??= $this->emptyYear($schoolYear);

            $field = match ($semester . ':' . $type) {
                'fall:midterm' => 'midterm_comment_s1',
                'fall:ptap' => 'ptap_comment_s1',
                'fall:attendance' => 'attendance_comment_s1',
                'spring:final' => 'final_comment_s2',
                'spring:ptap' => 'ptap_comment_s2',
                'spring:attendance' => 'attendance_comment_s2',
                default => null,
            };
            if ($field === null || $history[$studentId][$schoolYear][$field] !== '') {
                continue;
            }

            $comment = trim((string) ($row['comment'] ?? ''));
            $review = trim((string) ($row['comment_review'] ?? ''));
            $history[$studentId][$schoolYear][$field] = $type === 'attendance'
                ? ($comment !== '' ? $comment : $review)
                : ($review !== '' ? $review : $comment);
        }

        foreach ($this->decisionRows($studentIds) as $row) {
            $studentId = (int) ($row['student_id'] ?? 0);
            $schoolYear = trim((string) ($row['school_year'] ?? ''));
            if ($studentId <= 0 || $schoolYear === '') {
                continue;
            }

            $history[$studentId][$schoolYear] ??= $this->emptyYear($schoolYear);
            if ($history[$studentId][$schoolYear]['year_score'] === null) {
                $history[$studentId][$schoolYear]['year_score'] = $this->score($row['year_score'] ?? null);
            }
        }

        foreach ($history as &$studentHistory) {
            foreach ($studentHistory as &$year) {
                if ($year['year_score'] === null) {
                    $semesterScores = array_values(array_filter(
                        [$year['_semester_score_s1'], $year['_semester_score_s2']],
                        static fn($score): bool => $score !== null
                    ));
                    if ($semesterScores !== []) {
                        $year['year_score'] = round(array_sum($semesterScores) / count($semesterScores), 1);
                    }
                }
                unset($year['_semester_score_s1'], $year['_semester_score_s2']);
            }
            unset($year);
            krsort($studentHistory, SORT_STRING);
            $studentHistory = array_values($studentHistory);
        }
        unset($studentHistory);

        return $history;
    }

    private function latestSemesterRows(array $studentIds): array
    {
        if (!$this->db->tableExists('semester_scores')) {
            return [];
        }

        $rows = $this->db->table('semester_scores')
            ->select('id, student_id, school_year, semester, midterm_exam_score, final_exam_score, ptap_score, attendance_score, semester_score, updated_at')
            ->whereIn('student_id', $studentIds)
            ->orderBy('school_year', 'DESC')
            ->orderBy('updated_at', 'DESC')
            ->orderBy('id', 'DESC')
            ->get()
            ->getResultArray();

        $latest = [];
        foreach ($rows as $row) {
            $key = (int) ($row['student_id'] ?? 0)
                . '|' . trim((string) ($row['school_year'] ?? ''))
                . '|' . $this->normalizeSemester($row['semester'] ?? '');
            $latest[$key] ??= $row;
        }

        return array_values($latest);
    }

    private function commentRows(array $studentIds): array
    {
        if (!$this->db->tableExists('score_comments')) {
            return [];
        }

        $builder = $this->db->table('score_comments')
            ->select('id, student_id, school_year, semester, score_type, comment, comment_review')
            ->whereIn('student_id', $studentIds);
        if ($this->db->fieldExists('updated_at', 'score_comments')) {
            $builder->orderBy('updated_at', 'DESC');
        } elseif ($this->db->fieldExists('created_at', 'score_comments')) {
            $builder->orderBy('created_at', 'DESC');
        }

        return $builder->orderBy('id', 'DESC')->get()->getResultArray();
    }

    private function decisionRows(array $studentIds): array
    {
        if (!$this->db->tableExists('student_decisions')) {
            return [];
        }

        return $this->db->table('student_decisions')
            ->select('id, student_id, school_year, year_score')
            ->whereIn('student_id', $studentIds)
            ->orderBy('school_year', 'DESC')
            ->orderBy('updated_at', 'DESC')
            ->orderBy('id', 'DESC')
            ->get()
            ->getResultArray();
    }

    private function emptyYear(string $schoolYear): array
    {
        return [
            'school_year' => $schoolYear,
            'midterm_s1' => null,
            'midterm_comment_s1' => '',
            'ptap_s1' => null,
            'ptap_comment_s1' => '',
            'attendance_s1' => null,
            'attendance_comment_s1' => '',
            'final_s2' => null,
            'final_comment_s2' => '',
            'ptap_s2' => null,
            'ptap_comment_s2' => '',
            'attendance_s2' => null,
            'attendance_comment_s2' => '',
            'year_score' => null,
            '_semester_score_s1' => null,
            '_semester_score_s2' => null,
        ];
    }

    private function normalizeSemester($value): string
    {
        $semester = strtolower(trim((string) $value));
        return match ($semester) {
            'fall', 'first', 'first semester', 'semester 1', '1' => 'fall',
            'spring', 'second', 'second semester', 'semester 2', '2' => 'spring',
            default => $semester,
        };
    }

    private function normalizeCommentType($value): string
    {
        $type = strtolower(trim((string) $value));
        $type = trim((string) preg_replace('/[^a-z0-9]+/', '_', $type), '_');

        return match ($type) {
            'midterm_comment', 'midterm_comments' => 'midterm',
            'final_comment', 'final_comments' => 'final',
            'ptap_comment', 'ptap_comments' => 'ptap',
            'attendance_comment', 'attendance_comments', 'attendence', 'attendence_comment' => 'attendance',
            default => $type,
        };
    }

    private function score($value): ?float
    {
        return $value !== null && $value !== '' && is_numeric($value)
            ? round((float) $value, 2)
            : null;
    }
}