"""Renders one timetable grid per student (same grid as their batch, labeled per student)."""

import sys
import os

_ROOT = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "..")
sys.path.insert(0, os.path.join(_ROOT, "app"))
sys.path.insert(0, os.path.join(_ROOT, "controller"))

from xlsx_grid_helper import build_grid_sheet, new_workbook, save_workbook  # noqa: E402
from template_controller import DISPLAY_ROWS  # noqa: E402
from template_logger import log_error  # noqa: E402


def _sessions_for_batch(sessions, batch_code):
    return [s for s in sessions if batch_code in s["batch_codes"]]


def generate_student_wise_templates(sessions, data, output_dir):
    written = []
    for student in data["students"]:
        roll_no = student["roll_no"]
        batch_code = student["batch_code"]
        batch = data["batches_by_code"].get(batch_code)
        student_sessions = _sessions_for_batch(sessions, batch_code)

        # A student can only be in one place at a time: each (day, slot,
        # duration) must resolve to exactly one session. If the schedule
        # places more than one, that's a real scheduling error - log it
        # instead of silently picking/overwriting one.
        raw_by_day_slot = {}
        for s in student_sessions:
            for slot_index in s["slot_indices"]:
                raw_by_day_slot.setdefault((s["day"], slot_index, s["duration_minutes"]), []).append(s)

        by_day_slot = {}
        for (day, slot_index, duration_minutes), entries in raw_by_day_slot.items():
            if len(entries) > 1:
                course_list = ", ".join(
                    f'{e["course_id"]} Sec {e["section_id"]} ({e["course_type"]}) with {e["instructor_name"]} in {e["room_id"]}'
                    for e in entries
                )
                log_error(
                    f"Student conflict: roll {roll_no} (batch {batch_code}) has "
                    f"{len(entries)} overlapping courses on {day} slot {slot_index}: {course_list}"
                )
            by_day_slot[(day, slot_index, duration_minutes)] = entries[0]

        def cell_text(day, slot_index, duration_minutes, raw_by_day_slot=raw_by_day_slot):
            entries = raw_by_day_slot.get((day, slot_index, duration_minutes))
            if not entries:
                return ""
            s = entries[0]
            tag = " (Lab)" if s["course_type"] == "lab" else (" (General)" if s["is_general"] else "")
            text = f'{s["course_name"]}{tag} [Sec {s["section_id"]}]\n{s["instructor_name"]}\n{s["room_id"]}'
            if len(entries) > 1:
                text = "CONFLICT!\n" + text
            return text

        subtitle = f'{student["student_name"]} - Batch {batch_code}'
        if batch:
            subtitle += f' ({batch["department"]} - {batch["program"]})'

        wb = new_workbook()
        ws = wb.active
        build_grid_sheet(
            ws,
            title=f"Roll No: {roll_no}",
            subtitle=subtitle,
            display_rows=DISPLAY_ROWS,
            sessions_by_cell=by_day_slot,
            cell_text_fn=cell_text,
        )
        path = save_workbook(wb, output_dir, f"{roll_no}.xlsx")
        written.append(path)
    return written