package main

import (
	"encoding/json"
	"net/http"
	"strconv"
)

func (app *App) handleListShifts(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()
	var deptID *int
	if d := q.Get("dept"); d != "" {
		id, err := strconv.Atoi(d)
		if err == nil {
			deptID = &id
		}
	}

	claims := claimsFromContext(r)
	if claims.Role == "colead" && deptID == nil && len(claims.DeptIDs) > 0 {
		deptID = &claims.DeptIDs[0]
	}

	shifts, err := app.listShifts(deptID, q.Get("day"), q.Get("since"))
	if err != nil {
		writeError(w, err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, shifts)
}

func (app *App) handleCreateShift(w http.ResponseWriter, r *http.Request) {
	var s Shift
	if err := json.NewDecoder(r.Body).Decode(&s); err != nil {
		writeError(w, "invalid request", http.StatusBadRequest)
		return
	}
	if s.DepartmentID == 0 || s.Name == "" || s.Day == "" || s.StartTime == "" || s.EndTime == "" {
		writeError(w, "department_id, name, day, start_time, end_time required", http.StatusBadRequest)
		return
	}
	claims := claimsFromContext(r)
	if claims.Role == "colead" && !inSlice(s.DepartmentID, claims.DeptIDs) {
		writeError(w, "forbidden: outside your department", http.StatusForbidden)
		return
	}
	created, err := app.createShift(s)
	if err != nil {
		writeError(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusCreated)
	writeJSON(w, created)
}

func (app *App) handleUpdateShift(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.Atoi(r.PathValue("id"))
	if err != nil {
		writeError(w, "invalid id", http.StatusBadRequest)
		return
	}
	var s Shift
	if err := json.NewDecoder(r.Body).Decode(&s); err != nil {
		writeError(w, "invalid request", http.StatusBadRequest)
		return
	}
	claims := claimsFromContext(r)
	if claims.Role == "colead" {
		existing, _ := app.getShift(id)
		if existing == nil || !inSlice(existing.DepartmentID, claims.DeptIDs) {
			writeError(w, "forbidden: outside your department", http.StatusForbidden)
			return
		}
	}
	s.ID = id
	if err := app.updateShift(s); err != nil {
		writeError(w, err.Error(), http.StatusInternalServerError)
		return
	}
	updated, _ := app.getShift(id)
	writeJSON(w, updated)
}

func (app *App) handleDeleteShift(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.Atoi(r.PathValue("id"))
	if err != nil {
		writeError(w, "invalid id", http.StatusBadRequest)
		return
	}
	if err := app.deleteShift(id); err != nil {
		writeError(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// handleAssignShiftVolunteer is the shift-centric assignment endpoint.
// POST /api/shifts/:id/volunteers  body: {"volunteer_id": N, "force": false}
// Checks for scheduling conflicts unless force=true.
func (app *App) handleAssignShiftVolunteer(w http.ResponseWriter, r *http.Request) {
	shiftID, err := strconv.Atoi(r.PathValue("id"))
	if err != nil {
		writeError(w, "invalid shift id", http.StatusBadRequest)
		return
	}
	var body struct {
		VolunteerID int  `json:"volunteer_id"`
		Force       bool `json:"force"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil || body.VolunteerID == 0 {
		writeError(w, "volunteer_id required", http.StatusBadRequest)
		return
	}

	if !body.Force {
		conflicts, err := app.checkShiftConflict(body.VolunteerID, shiftID)
		if err != nil {
			writeError(w, err.Error(), http.StatusInternalServerError)
			return
		}
		if len(conflicts) > 0 {
			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusConflict)
			writeJSON(w, map[string]any{
				"conflict":           true,
				"conflicting_shifts": conflicts,
			})
			return
		}
	}

	if err := app.assignShift(body.VolunteerID, shiftID); err != nil {
		writeError(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// handleUnassignShiftVolunteer removes a volunteer from a shift.
// DELETE /api/shifts/:id/volunteers/:volunteer_id
func (app *App) handleUnassignShiftVolunteer(w http.ResponseWriter, r *http.Request) {
	shiftID, err := strconv.Atoi(r.PathValue("id"))
	if err != nil {
		writeError(w, "invalid shift id", http.StatusBadRequest)
		return
	}
	volunteerID, err := strconv.Atoi(r.PathValue("volunteer_id"))
	if err != nil {
		writeError(w, "invalid volunteer id", http.StatusBadRequest)
		return
	}
	if err := app.unassignShift(volunteerID, shiftID); err != nil {
		writeError(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// handleReorderShifts bulk-updates shift positions.
// POST /api/shifts/reorder  body: [{"id": N, "position": N}, ...]
func (app *App) handleReorderShifts(w http.ResponseWriter, r *http.Request) {
	var raw []struct {
		ID       int `json:"id"`
		Position int `json:"position"`
	}
	if err := json.NewDecoder(r.Body).Decode(&raw); err != nil || len(raw) == 0 {
		writeError(w, "array of {id, position} required", http.StatusBadRequest)
		return
	}
	positions := make([]struct{ ID, Position int }, len(raw))
	for i, p := range raw {
		positions[i] = struct{ ID, Position int }{p.ID, p.Position}
	}
	if err := app.reorderShifts(positions); err != nil {
		writeError(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}