"""Renders one timetable grid per instructor."""

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 TIME_SLOTS as GRID_TIME_SLOTS  # noqa: E402
from template_logger import log_error  # noqa: E402


def generate_teacher_wise_templates(sessions, data, output_dir):
    written = []

    # instructors.csv has one row per (instructor, course, section) teaching
    # assignment, so the same instructor_code can repeat; render one sheet
    # per unique instructor, listing all of their assignments in the subtitle.
    seen_codes = []
    assignments_by_code = {}
    name_by_code = {}
    for row in data["instructors"]:
        code = row["instructor_code"]
        if code not in assignments_by_code:
            seen_codes.append(code)
            assignments_by_code[code] = []
            name_by_code[code] = row["instructor_name"]
        assignments_by_code[code].append(f'{row["course_id"]} (Sec {row["section_id"]})')

    for code in seen_codes:
        instructor_name = name_by_code[code]
        instr_sessions = [s for s in sessions if s["instructor_code"] == code]

        # A teacher can only be in one place at a time: each (day, slot)
        # 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 instr_sessions:
            for slot_index in s["slot_indices"]:
                raw_by_day_slot.setdefault((s["day"], slot_index), []).append(s)

        by_day_slot = {}
        for (day, slot_index), entries in raw_by_day_slot.items():
            if len(entries) > 1:
                course_list = ", ".join(
                    f'{e["course_id"]} ({e["course_type"]}) for batch(es) {"+".join(e["batch_codes"])} in {e["room_id"]}'
                    for e in entries
                )
                log_error(
                    f"Teacher conflict: {instructor_name} ({code}) is double-booked on "
                    f"{day} slot {slot_index}: {course_list}"
                )
            by_day_slot[(day, slot_index)] = entries[0]

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

        subtitle = "Teaches: " + ", ".join(assignments_by_code[code])

        wb = new_workbook()
        ws = wb.active
        build_grid_sheet(
            ws,
            title=f'{instructor_name} ({code})',
            subtitle=subtitle,
            time_slots=GRID_TIME_SLOTS,
            sessions_by_day_slot=by_day_slot,
            cell_text_fn=cell_text,
        )
        path = save_workbook(wb, output_dir, f"{code}.xlsx")
        written.append(path)
    return written