import { useCallback, useEffect, useRef, useState } from 'react'
import type { StructuredGrid, GridZone, LayoutDividers } from './types'

const KLAUSUR_API = '/klausur-api'
const MAX_UNDO = 50

export interface GridEditorState {
  grid: StructuredGrid | null
  loading: boolean
  saving: boolean
  error: string | null
  dirty: boolean
  selectedCell: string | null
  selectedZone: number | null
}

export type IpaMode = 'auto' | 'all' | 'en' | 'none'
export type SyllableMode = 'auto' | 'all' | 'de' | 'en' | 'none'

export function useGridEditor(sessionId: string | null) {
  const [grid, setGrid] = useState<StructuredGrid | null>(null)
  const [loading, setLoading] = useState(false)
  const [saving, setSaving] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const [dirty, setDirty] = useState(false)
  const [selectedCell, setSelectedCell] = useState<string | null>(null)
  const [selectedZone, setSelectedZone] = useState<number | null>(null)
  const [ipaMode, setIpaMode] = useState<IpaMode>('auto')
  const [syllableMode, setSyllableMode] = useState<SyllableMode>('auto')

  // Undo/redo stacks store serialized zone arrays
  const undoStack = useRef<string[]>([])
  const redoStack = useRef<string[]>([])

  const pushUndo = useCallback((zones: GridZone[]) => {
    undoStack.current.push(JSON.stringify(zones))
    if (undoStack.current.length > MAX_UNDO) {
      undoStack.current.shift()
    }
    redoStack.current = []
  }, [])

  // ------------------------------------------------------------------
  // Load / Build
  // ------------------------------------------------------------------

  const buildGrid = useCallback(async () => {
    if (!sessionId) return
    setLoading(true)
    setError(null)
    try {
      const params = new URLSearchParams()
      params.set('ipa_mode', ipaMode)
      params.set('syllable_mode', syllableMode)
      const res = await fetch(
        `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/build-grid?${params}`,
        { method: 'POST' },
      )
      if (!res.ok) {
        const data = await res.json().catch(() => ({}))
        throw new Error(data.detail || `HTTP ${res.status}`)
      }
      const data: StructuredGrid = await res.json()
      setGrid(data)
      setDirty(false)
      undoStack.current = []
      redoStack.current = []
    } catch (e) {
      setError(e instanceof Error ? e.message : String(e))
    } finally {
      setLoading(false)
    }
  }, [sessionId, ipaMode, syllableMode])

  const loadGrid = useCallback(async () => {
    if (!sessionId) return
    setLoading(true)
    setError(null)
    try {
      const res = await fetch(
        `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/grid-editor`,
      )
      if (res.status === 404) {
        // No grid yet — build it
        await buildGrid()
        return
      }
      if (!res.ok) {
        const data = await res.json().catch(() => ({}))
        throw new Error(data.detail || `HTTP ${res.status}`)
      }
      const data: StructuredGrid = await res.json()
      setGrid(data)
      setDirty(false)
      undoStack.current = []
      redoStack.current = []
    } catch (e) {
      setError(e instanceof Error ? e.message : String(e))
    } finally {
      setLoading(false)
    }
  }, [sessionId, buildGrid])

  // Auto-rebuild when IPA or syllable mode changes (skip initial mount)
  const initialLoadDone = useRef(false)
  useEffect(() => {
    if (!initialLoadDone.current) {
      // Mark as initialized once the first grid is loaded
      if (grid) initialLoadDone.current = true
      return
    }
    // Mode changed after initial load — rebuild
    buildGrid()
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [ipaMode, syllableMode])

  // ------------------------------------------------------------------
  // Save
  // ------------------------------------------------------------------

  const saveGrid = useCallback(async () => {
    if (!sessionId || !grid) return
    setSaving(true)
    try {
      const res = await fetch(
        `${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/save-grid`,
        {
          method: 'POST',
          headers: { 'Content-Type': 'application/json' },
          body: JSON.stringify(grid),
        },
      )
      if (!res.ok) {
        const data = await res.json().catch(() => ({}))
        throw new Error(data.detail || `HTTP ${res.status}`)
      }
      setDirty(false)
    } catch (e) {
      setError(e instanceof Error ? e.message : String(e))
    } finally {
      setSaving(false)
    }
  }, [sessionId, grid])

  // ------------------------------------------------------------------
  // Cell editing
  // ------------------------------------------------------------------

  const updateCellText = useCallback(
    (cellId: string, newText: string) => {
      if (!grid) return
      pushUndo(grid.zones)

      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((zone) => {
            // Check if cell exists
            const existing = zone.cells.find((c) => c.cell_id === cellId)
            if (existing) {
              return {
                ...zone,
                cells: zone.cells.map((cell) =>
                  cell.cell_id === cellId ? { ...cell, text: newText } : cell,
                ),
              }
            }
            // Cell doesn't exist — create it if the cellId belongs to this zone
            // cellId format: Z{zone}_R{row}_C{col}
            const match = cellId.match(/^Z(\d+)_R(\d+)_C(\d+)$/)
            if (!match || parseInt(match[1]) !== zone.zone_index) return zone
            const rowIndex = parseInt(match[2])
            const colIndex = parseInt(match[3])
            const col = zone.columns.find((c) => c.index === colIndex)
            const newCell = {
              cell_id: cellId,
              zone_index: zone.zone_index,
              row_index: rowIndex,
              col_index: colIndex,
              col_type: col?.label ?? '',
              text: newText,
              confidence: 0,
              bbox_px: { x: 0, y: 0, w: 0, h: 0 },
              bbox_pct: { x: 0, y: 0, w: 0, h: 0 },
              word_boxes: [],
              ocr_engine: 'manual',
              is_bold: false,
            }
            return { ...zone, cells: [...zone.cells, newCell] }
          }),
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  // ------------------------------------------------------------------
  // Column formatting
  // ------------------------------------------------------------------

  const toggleColumnBold = useCallback(
    (zoneIndex: number, colIndex: number) => {
      if (!grid) return
      pushUndo(grid.zones)

      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((zone) => {
            if (zone.zone_index !== zoneIndex) return zone
            const col = zone.columns.find((c) => c.index === colIndex)
            const newBold = col ? !col.bold : true
            return {
              ...zone,
              columns: zone.columns.map((c) =>
                c.index === colIndex ? { ...c, bold: newBold } : c,
              ),
              cells: zone.cells.map((cell) =>
                cell.col_index === colIndex
                  ? { ...cell, is_bold: newBold }
                  : cell,
              ),
            }
          }),
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  // ------------------------------------------------------------------
  // Row formatting
  // ------------------------------------------------------------------

  const toggleRowHeader = useCallback(
    (zoneIndex: number, rowIndex: number) => {
      if (!grid) return
      pushUndo(grid.zones)

      // Cycle: normal → header → footer → normal
      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((zone) => {
            if (zone.zone_index !== zoneIndex) return zone
            return {
              ...zone,
              rows: zone.rows.map((r) => {
                if (r.index !== rowIndex) return r
                if (!r.is_header && !r.is_footer) {
                  return { ...r, is_header: true, is_footer: false }
                } else if (r.is_header) {
                  return { ...r, is_header: false, is_footer: true }
                } else {
                  return { ...r, is_header: false, is_footer: false }
                }
              }),
            }
          }),
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  // ------------------------------------------------------------------
  // Column management
  // ------------------------------------------------------------------

  const deleteColumn = useCallback(
    (zoneIndex: number, colIndex: number) => {
      if (!grid) return
      const zone = grid.zones.find((z) => z.zone_index === zoneIndex)
      if (!zone || zone.columns.length <= 1) return // keep at least 1 column
      pushUndo(grid.zones)

      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((z) => {
            if (z.zone_index !== zoneIndex) return z
            const deletedCol = z.columns.find((c) => c.index === colIndex)
            const newColumns = z.columns
              .filter((c) => c.index !== colIndex)
              .map((c, i) => {
                const result = { ...c, index: i, label: `column_${i + 1}` }
                // Merge x-boundary: previous column absorbs deleted column's space
                if (deletedCol) {
                  if (c.index === colIndex - 1) {
                    result.x_max_pct = deletedCol.x_max_pct
                    result.x_max_px = deletedCol.x_max_px
                  } else if (colIndex === 0 && c.index === 1) {
                    result.x_min_pct = deletedCol.x_min_pct
                    result.x_min_px = deletedCol.x_min_px
                  }
                }
                return result
              })
            const newCells = z.cells
              .filter((c) => c.col_index !== colIndex)
              .map((c) => {
                const newCI = c.col_index > colIndex ? c.col_index - 1 : c.col_index
                return {
                  ...c,
                  col_index: newCI,
                  cell_id: `Z${zoneIndex}_R${String(c.row_index).padStart(2, '0')}_C${newCI}`,
                }
              })
            return { ...z, columns: newColumns, cells: newCells }
          }),
          summary: {
            ...prev.summary,
            total_columns: prev.summary.total_columns - 1,
            total_cells: prev.zones.reduce(
              (sum, z) =>
                sum +
                (z.zone_index === zoneIndex
                  ? z.cells.filter((c) => c.col_index !== colIndex).length
                  : z.cells.length),
              0,
            ),
          },
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  const addColumn = useCallback(
    (zoneIndex: number, afterColIndex: number) => {
      if (!grid) return
      const zone = grid.zones.find((z) => z.zone_index === zoneIndex)
      if (!zone) return
      pushUndo(grid.zones)

      const newColIndex = afterColIndex + 1

      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((z) => {
            if (z.zone_index !== zoneIndex) return z
            // Shift existing columns
            const shiftedCols = z.columns.map((c) =>
              c.index > afterColIndex ? { ...c, index: c.index + 1, label: `column_${c.index + 2}` } : c,
            )
            // Insert new column
            const refCol = z.columns.find((c) => c.index === afterColIndex) || z.columns[z.columns.length - 1]
            const newCol = {
              index: newColIndex,
              label: `column_${newColIndex + 1}`,
              x_min_px: refCol.x_max_px,
              x_max_px: refCol.x_max_px + (refCol.x_max_px - refCol.x_min_px),
              x_min_pct: refCol.x_max_pct,
              x_max_pct: Math.min(100, refCol.x_max_pct + (refCol.x_max_pct - refCol.x_min_pct)),
              bold: false,
            }
            const allCols = [...shiftedCols, newCol].sort((a, b) => a.index - b.index)

            // Shift existing cells and create empty cells for new column
            const shiftedCells = z.cells.map((c) => {
              if (c.col_index > afterColIndex) {
                const newCI = c.col_index + 1
                return {
                  ...c,
                  col_index: newCI,
                  cell_id: `Z${zoneIndex}_R${String(c.row_index).padStart(2, '0')}_C${newCI}`,
                }
              }
              return c
            })
            // Create empty cells for each row
            const newCells = z.rows.map((row) => ({
              cell_id: `Z${zoneIndex}_R${String(row.index).padStart(2, '0')}_C${newColIndex}`,
              zone_index: zoneIndex,
              row_index: row.index,
              col_index: newColIndex,
              col_type: `column_${newColIndex + 1}`,
              text: '',
              confidence: 0,
              bbox_px: { x: 0, y: 0, w: 0, h: 0 },
              bbox_pct: { x: 0, y: 0, w: 0, h: 0 },
              word_boxes: [],
              ocr_engine: 'manual',
              is_bold: false,
            }))

            return { ...z, columns: allCols, cells: [...shiftedCells, ...newCells] }
          }),
          summary: {
            ...prev.summary,
            total_columns: prev.summary.total_columns + 1,
            total_cells: prev.summary.total_cells + (zone?.rows.length ?? 0),
          },
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  // ------------------------------------------------------------------
  // Row management
  // ------------------------------------------------------------------

  const deleteRow = useCallback(
    (zoneIndex: number, rowIndex: number) => {
      if (!grid) return
      const zone = grid.zones.find((z) => z.zone_index === zoneIndex)
      if (!zone || zone.rows.length <= 1) return // keep at least 1 row
      pushUndo(grid.zones)

      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((z) => {
            if (z.zone_index !== zoneIndex) return z
            const newRows = z.rows
              .filter((r) => r.index !== rowIndex)
              .map((r, i) => ({ ...r, index: i }))
            const newCells = z.cells
              .filter((c) => c.row_index !== rowIndex)
              .map((c) => {
                const newRI = c.row_index > rowIndex ? c.row_index - 1 : c.row_index
                return {
                  ...c,
                  row_index: newRI,
                  cell_id: `Z${zoneIndex}_R${String(newRI).padStart(2, '0')}_C${c.col_index}`,
                }
              })
            return { ...z, rows: newRows, cells: newCells }
          }),
          summary: {
            ...prev.summary,
            total_rows: prev.summary.total_rows - 1,
            total_cells: prev.zones.reduce(
              (sum, z) =>
                sum +
                (z.zone_index === zoneIndex
                  ? z.cells.filter((c) => c.row_index !== rowIndex).length
                  : z.cells.length),
              0,
            ),
          },
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  const addRow = useCallback(
    (zoneIndex: number, afterRowIndex: number) => {
      if (!grid) return
      const zone = grid.zones.find((z) => z.zone_index === zoneIndex)
      if (!zone) return
      pushUndo(grid.zones)

      const newRowIndex = afterRowIndex + 1

      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((z) => {
            if (z.zone_index !== zoneIndex) return z
            // Shift existing rows
            const shiftedRows = z.rows.map((r) =>
              r.index > afterRowIndex ? { ...r, index: r.index + 1 } : r,
            )
            // Insert new row
            const refRow = z.rows.find((r) => r.index === afterRowIndex) || z.rows[z.rows.length - 1]
            const newRow = {
              index: newRowIndex,
              y_min_px: refRow.y_max_px,
              y_max_px: refRow.y_max_px + (refRow.y_max_px - refRow.y_min_px),
              y_min_pct: refRow.y_max_pct,
              y_max_pct: Math.min(100, refRow.y_max_pct + (refRow.y_max_pct - refRow.y_min_pct)),
              is_header: false,
              is_footer: false,
            }
            const allRows = [...shiftedRows, newRow].sort((a, b) => a.index - b.index)

            // Shift existing cells
            const shiftedCells = z.cells.map((c) => {
              if (c.row_index > afterRowIndex) {
                const newRI = c.row_index + 1
                return {
                  ...c,
                  row_index: newRI,
                  cell_id: `Z${zoneIndex}_R${String(newRI).padStart(2, '0')}_C${c.col_index}`,
                }
              }
              return c
            })
            // Create empty cells for each column
            const newCells = z.columns.map((col) => ({
              cell_id: `Z${zoneIndex}_R${String(newRowIndex).padStart(2, '0')}_C${col.index}`,
              zone_index: zoneIndex,
              row_index: newRowIndex,
              col_index: col.index,
              col_type: col.label,
              text: '',
              confidence: 0,
              bbox_px: { x: 0, y: 0, w: 0, h: 0 },
              bbox_pct: { x: 0, y: 0, w: 0, h: 0 },
              word_boxes: [],
              ocr_engine: 'manual',
              is_bold: false,
            }))

            return { ...z, rows: allRows, cells: [...shiftedCells, ...newCells] }
          }),
          summary: {
            ...prev.summary,
            total_rows: prev.summary.total_rows + 1,
            total_cells: prev.summary.total_cells + (zone?.columns.length ?? 0),
          },
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  // ------------------------------------------------------------------
  // Layout editing (image overlay)
  // ------------------------------------------------------------------

  /** Capture current state for undo — call once at drag start. */
  const commitUndoPoint = useCallback(() => {
    if (!grid) return
    pushUndo(grid.zones)
  }, [grid, pushUndo])

  /** Move a column boundary. boundaryIndex 0 = left edge of col 0, etc. */
  const updateColumnDivider = useCallback(
    (zoneIndex: number, boundaryIndex: number, newXPct: number) => {
      if (!grid) return
      setGrid((prev) => {
        if (!prev) return prev
        const imgW = prev.image_width || 1
        const newPx = Math.round((newXPct / 100) * imgW)
        return {
          ...prev,
          zones: prev.zones.map((z) => {
            if (z.zone_index !== zoneIndex) return z
            return {
              ...z,
              columns: z.columns.map((col) => {
                // Right edge of the column before this boundary
                if (col.index === boundaryIndex - 1) {
                  return { ...col, x_max_pct: newXPct, x_max_px: newPx }
                }
                // Left edge of the column at this boundary
                if (col.index === boundaryIndex) {
                  return { ...col, x_min_pct: newXPct, x_min_px: newPx }
                }
                return col
              }),
            }
          }),
        }
      })
      setDirty(true)
    },
    [grid],
  )

  /** Update horizontal layout guidelines (margins, header, footer). */
  const updateLayoutHorizontals = useCallback(
    (horizontals: LayoutDividers['horizontals']) => {
      if (!grid) return
      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          layout_dividers: {
            ...(prev.layout_dividers || { horizontals: {} }),
            horizontals,
          },
        }
      })
      setDirty(true)
    },
    [grid],
  )

  /** Split a column at a given x percentage, creating a new column. */
  const splitColumnAt = useCallback(
    (zoneIndex: number, xPct: number) => {
      if (!grid) return
      const zone = grid.zones.find((z) => z.zone_index === zoneIndex)
      if (!zone) return

      const sorted = [...zone.columns].sort((a, b) => a.index - b.index)
      const targetCol = sorted.find((c) => c.x_min_pct <= xPct && c.x_max_pct >= xPct)
      if (!targetCol) return

      pushUndo(grid.zones)
      const newColIndex = targetCol.index + 1
      const imgW = grid.image_width || 1

      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((z) => {
            if (z.zone_index !== zoneIndex) return z
            const leftCol = {
              ...targetCol,
              x_max_pct: xPct,
              x_max_px: Math.round((xPct / 100) * imgW),
            }
            const rightCol = {
              index: newColIndex,
              label: `column_${newColIndex + 1}`,
              x_min_pct: xPct,
              x_max_pct: targetCol.x_max_pct,
              x_min_px: Math.round((xPct / 100) * imgW),
              x_max_px: targetCol.x_max_px,
              bold: false,
            }
            const updatedCols = z.columns.map((c) => {
              if (c.index === targetCol.index) return leftCol
              if (c.index > targetCol.index) return { ...c, index: c.index + 1, label: `column_${c.index + 2}` }
              return c
            })
            const allCols = [...updatedCols, rightCol].sort((a, b) => a.index - b.index)
            const shiftedCells = z.cells.map((c) => {
              if (c.col_index > targetCol.index) {
                const newCI = c.col_index + 1
                return {
                  ...c,
                  col_index: newCI,
                  cell_id: `Z${zoneIndex}_R${String(c.row_index).padStart(2, '0')}_C${newCI}`,
                }
              }
              return c
            })
            const newCells = z.rows.map((row) => ({
              cell_id: `Z${zoneIndex}_R${String(row.index).padStart(2, '0')}_C${newColIndex}`,
              zone_index: zoneIndex,
              row_index: row.index,
              col_index: newColIndex,
              col_type: `column_${newColIndex + 1}`,
              text: '',
              confidence: 0,
              bbox_px: { x: 0, y: 0, w: 0, h: 0 },
              bbox_pct: { x: 0, y: 0, w: 0, h: 0 },
              word_boxes: [],
              ocr_engine: 'manual',
              is_bold: false,
            }))
            return { ...z, columns: allCols, cells: [...shiftedCells, ...newCells] }
          }),
          summary: {
            ...prev.summary,
            total_columns: prev.summary.total_columns + 1,
            total_cells: prev.summary.total_cells + (zone.rows.length),
          },
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  // ------------------------------------------------------------------
  // Column pattern auto-correction
  // ------------------------------------------------------------------

  /**
   * Detect dominant prefix+number patterns per column and complete
   * partial matches.  E.g. if 3+ cells read "p.70", "p.71", etc.,
   * a cell reading ".65" is corrected to "p.65".
   * Returns the number of corrections made.
   */
  const autoCorrectColumnPatterns = useCallback(() => {
    if (!grid) return 0
    pushUndo(grid.zones)

    let totalFixed = 0
    const numberPattern = /^(.+?)(\d+)\s*$/

    setGrid((prev) => {
      if (!prev) return prev
      return {
        ...prev,
        zones: prev.zones.map((zone) => {
          // Group cells by column
          const cellsByCol = new Map<number, { cell: (typeof zone.cells)[0]; idx: number }[]>()
          zone.cells.forEach((cell, idx) => {
            const arr = cellsByCol.get(cell.col_index) || []
            arr.push({ cell, idx })
            cellsByCol.set(cell.col_index, arr)
          })

          const newCells = [...zone.cells]

          for (const [, colEntries] of cellsByCol) {
            // Count prefix occurrences
            const prefixCounts = new Map<string, number>()
            for (const { cell } of colEntries) {
              const m = cell.text.trim().match(numberPattern)
              if (m) {
                prefixCounts.set(m[1], (prefixCounts.get(m[1]) || 0) + 1)
              }
            }

            // Find dominant prefix (>= 3 occurrences)
            let dominantPrefix = ''
            let maxCount = 0
            for (const [prefix, count] of prefixCounts) {
              if (count >= 3 && count > maxCount) {
                dominantPrefix = prefix
                maxCount = count
              }
            }
            if (!dominantPrefix) continue

            // Fix partial matches — entries that are just [.?\s*]NUMBER
            for (const { cell, idx } of colEntries) {
              const text = cell.text.trim()
              if (!text || text.startsWith(dominantPrefix)) continue

              const numMatch = text.match(/^[.\s]*(\d+)\s*$/)
              if (numMatch) {
                newCells[idx] = { ...newCells[idx], text: `${dominantPrefix}${numMatch[1]}` }
                totalFixed++
              }
            }
          }

          return { ...zone, cells: newCells }
        }),
      }
    })

    if (totalFixed > 0) setDirty(true)
    return totalFixed
  }, [grid, pushUndo])

  // ------------------------------------------------------------------
  // Multi-select & bulk formatting
  // ------------------------------------------------------------------

  const [selectedCells, setSelectedCells] = useState<Set<string>>(new Set())

  const toggleCellSelection = useCallback(
    (cellId: string) => {
      setSelectedCells((prev) => {
        const next = new Set(prev)
        if (next.has(cellId)) next.delete(cellId)
        else next.add(cellId)
        return next
      })
    },
    [],
  )

  const clearCellSelection = useCallback(() => {
    setSelectedCells(new Set())
  }, [])

  /**
   * Set a manual color override on a cell.
   * - hex string (e.g. "#dc2626"): force text color
   * - null: force no color (clear bar)
   * - undefined: remove override, restore OCR-detected color
   */
  const setCellColor = useCallback(
    (cellId: string, color: string | null | undefined) => {
      if (!grid) return
      pushUndo(grid.zones)
      setGrid((prev) => {
        if (!prev) return prev
        return {
          ...prev,
          zones: prev.zones.map((zone) => ({
            ...zone,
            cells: zone.cells.map((cell) => {
              if (cell.cell_id !== cellId) return cell
              if (color === undefined) {
                // Remove override entirely — restore OCR behavior
                const { color_override: _, ...rest } = cell
                return rest
              }
              return { ...cell, color_override: color }
            }),
          })),
        }
      })
      setDirty(true)
    },
    [grid, pushUndo],
  )

  /** Toggle bold on all selected cells (and their columns). */
  const toggleSelectedBold = useCallback(() => {
    if (!grid || selectedCells.size === 0) return
    pushUndo(grid.zones)

    // Determine if we're turning bold on or off (majority rule)
    const cells = grid.zones.flatMap((z) => z.cells)
    const selectedArr = cells.filter((c) => selectedCells.has(c.cell_id))
    const boldCount = selectedArr.filter((c) => c.is_bold).length
    const newBold = boldCount < selectedArr.length / 2

    setGrid((prev) => {
      if (!prev) return prev
      return {
        ...prev,
        zones: prev.zones.map((zone) => ({
          ...zone,
          cells: zone.cells.map((cell) =>
            selectedCells.has(cell.cell_id) ? { ...cell, is_bold: newBold } : cell,
          ),
        })),
      }
    })
    setDirty(true)
    setSelectedCells(new Set())
  }, [grid, selectedCells, pushUndo])

  // ------------------------------------------------------------------
  // Undo / Redo
  // ------------------------------------------------------------------

  const undo = useCallback(() => {
    if (!grid || undoStack.current.length === 0) return
    redoStack.current.push(JSON.stringify(grid.zones))
    const prev = undoStack.current.pop()!
    setGrid((g) => (g ? { ...g, zones: JSON.parse(prev) } : g))
    setDirty(true)
  }, [grid])

  const redo = useCallback(() => {
    if (!grid || redoStack.current.length === 0) return
    undoStack.current.push(JSON.stringify(grid.zones))
    const next = redoStack.current.pop()!
    setGrid((g) => (g ? { ...g, zones: JSON.parse(next) } : g))
    setDirty(true)
  }, [grid])

  const canUndo = undoStack.current.length > 0
  const canRedo = redoStack.current.length > 0

  // ------------------------------------------------------------------
  // Navigation helpers
  // ------------------------------------------------------------------

  const getAdjacentCell = useCallback(
    (cellId: string, direction: 'up' | 'down' | 'left' | 'right'): string | null => {
      if (!grid) return null
      for (const zone of grid.zones) {
        // Find the cell or derive row/col from cellId pattern
        const cell = zone.cells.find((c) => c.cell_id === cellId)
        let currentRow: number, currentCol: number
        if (cell) {
          currentRow = cell.row_index
          currentCol = cell.col_index
        } else {
          // Try to parse from cellId: Z{zone}_R{row}_C{col}
          const match = cellId.match(/^Z(\d+)_R(\d+)_C(\d+)$/)
          if (!match || parseInt(match[1]) !== zone.zone_index) continue
          currentRow = parseInt(match[2])
          currentCol = parseInt(match[3])
        }

        let targetRow = currentRow
        let targetCol = currentCol
        if (direction === 'up') targetRow--
        if (direction === 'down') targetRow++
        if (direction === 'left') targetCol--
        if (direction === 'right') targetCol++

        // Check bounds
        const hasRow = zone.rows.some((r) => r.index === targetRow)
        const hasCol = zone.columns.some((c) => c.index === targetCol)
        if (!hasRow || !hasCol) return null

        // Return existing cell ID or construct one
        const target = zone.cells.find(
          (c) => c.row_index === targetRow && c.col_index === targetCol,
        )
        return target?.cell_id ?? `Z${zone.zone_index}_R${String(targetRow).padStart(2, '0')}_C${targetCol}`
      }
      return null
    },
    [grid],
  )

  return {
    grid,
    loading,
    saving,
    error,
    dirty,
    selectedCell,
    selectedZone,
    selectedCells,
    setSelectedCell,
    setSelectedZone,
    buildGrid,
    loadGrid,
    saveGrid,
    updateCellText,
    toggleColumnBold,
    toggleRowHeader,
    undo,
    redo,
    canUndo,
    canRedo,
    getAdjacentCell,
    deleteColumn,
    addColumn,
    deleteRow,
    addRow,
    commitUndoPoint,
    updateColumnDivider,
    updateLayoutHorizontals,
    splitColumnAt,
    toggleCellSelection,
    clearCellSelection,
    toggleSelectedBold,
    autoCorrectColumnPatterns,
    setCellColor,
    ipaMode,
    setIpaMode,
    syllableMode,
    setSyllableMode,
  }
}