// Copyright 2017 FoxyUtils ehf. All rights reserved.
//
// Use of this source code is governed by the terms of the Affero GNU General
// Public License version 3.0 as published by the Free Software Foundation and
// appearing in the file LICENSE included in the packaging of this file. A
// commercial license can be purchased on https://unidoc.io.

package spreadsheet

import (
	"fmt"
	"time"
	"regexp"
	"strconv"
	"strings"

	"github.com/unidoc/unioffice/spreadsheet/formula"
	"github.com/unidoc/unioffice/spreadsheet/reference"
)

func newEvalContext(s *Sheet) *evalContext {
	return &evalContext{s: s, evaluating: make(map[string]struct{})}
}

type evalContext struct {
	s              *Sheet
	colOff, rowOff uint32
	evaluating     map[string]struct{}
}

func (e *evalContext) Cell(ref string, ev formula.Evaluator) formula.Result {
	if !validateRef(ref) {
		return formula.MakeErrorResultType(formula.ErrorTypeName, "")
	}
	fullRef := e.s.Name() + "!" + ref
	if cached, found := ev.GetFromCache(fullRef); found {
		return cached
	}
	cr, err := reference.ParseCellReference(ref)
	if err != nil {
		return formula.MakeErrorResult(fmt.Sprintf("error parsing %s: %s", ref, err))
	}

	// offsets are used in shared formulas so that references like 'A1', '$A1',
	// 'A$1', '$A$1' will behave differently according to the offset
	if e.colOff != 0 && !cr.AbsoluteColumn {
		cr.ColumnIdx += e.colOff
		cr.Column = reference.IndexToColumn(cr.ColumnIdx)
	}
	if e.rowOff != 0 && !cr.AbsoluteRow {
		cr.RowIdx += e.rowOff
	}

	c := e.s.Cell(cr.String())

	// if we have a formula, evaluate it
	if c.HasFormula() {
		if _, ok := e.evaluating[ref]; ok {
			// recursively evaluating, so bail out
			return formula.MakeErrorResult("recursion detected during evaluation of " + ref)
		}
		e.evaluating[ref] = struct{}{}
		res := ev.Eval(e, c.GetFormula())
		delete(e.evaluating, ref)
		ev.SetCache(fullRef, res)
		return res
	}

	if c.IsEmpty() {
		res := formula.MakeEmptyResult()
		ev.SetCache(fullRef, res)
		return res
	} else if c.IsNumber() {
		v, _ := c.GetValueAsNumber()
		res := formula.MakeNumberResult(v)
		ev.SetCache(fullRef, res)
		return res
	} else if c.IsBool() {
		v, _ := c.GetValueAsBool()
		res := formula.MakeBoolResult(v)
		ev.SetCache(fullRef, res)
		return res
	}

	v, _ := c.GetRawValue()

	if c.IsError() {
		errRes := formula.MakeErrorResult("")
		errRes.ValueString = v
		ev.SetCache(fullRef, errRes)
		return errRes
	}
	res := formula.MakeStringResult(v)
	ev.SetCache(fullRef, res)
	return res
}

func (e *evalContext) Sheet(name string) formula.Context {
	for _, sheet := range e.s.w.Sheets() {
		if sheet.Name() == name {
			return sheet.FormulaContext()
		}
	}
	return formula.InvalidReferenceContext
}

func (e *evalContext) NamedRange(ref string) formula.Reference {
	for _, dn := range e.s.w.DefinedNames() {
		if dn.Name() == ref {
			return formula.MakeRangeReference(dn.Content())
		}
	}
	for _, tbl := range e.s.w.Tables() {
		if tbl.Name() == ref {
			return formula.MakeRangeReference(fmt.Sprintf("%s!%s", e.s.Name(), tbl.Reference()))
		}
	}
	return formula.ReferenceInvalid
}

func (e *evalContext) SetOffset(col, row uint32) {
	e.colOff = col
	e.rowOff = row
}

// GetFilename returns the filename of the context's workbook.
func (e *evalContext) GetFilename() string {
	return e.s.w.GetFilename()
}

// GetFormat returns a cell data format.
func (e *evalContext) GetFormat(cellRef string) string {
	return e.s.Cell(cellRef).getFormat()
}

// GetLabelPrefix returns label prefix which depends on the cell's horizontal alignment.
func (e *evalContext) GetLabelPrefix(cellRef string) string {
	return e.s.Cell(cellRef).getLabelPrefix()
}

// GetLocked returns true if the cell is locked.
func (e *evalContext) GetLocked(cellRef string) bool {
	return e.s.Cell(cellRef).getLocked()
}

// HasFormula returns true if the cell contains formula.
func (e *evalContext) HasFormula(cellRef string) bool {
	return e.s.Cell(cellRef).HasFormula()
}

// IsBool returns true if the cell boolean value.
func (e *evalContext) IsBool(cellRef string) bool {
	return e.s.Cell(cellRef).IsBool()
}

// SetLocked sets cell locked or not.
func (e *evalContext) SetLocked(cellRef string, locked bool) {
	e.s.Cell(cellRef).setLocked(locked)
}

// GetWidth returns a worksheet's column width.
func (e *evalContext) GetWidth(colIdx int) float64 {
	colIdx++
	for _, c := range e.s.X().Cols[0].Col {
		if int(c.MinAttr) <= colIdx && colIdx <= int(c.MaxAttr) {
			return float64(int(*c.WidthAttr))
		}
	}
	return 0
}

// GetEpoch returns a workbook's time epoch.
func (e *evalContext) GetEpoch() time.Time {
	return e.s.w.Epoch()
}

// dbcs is a list of languages which use DBCS or double-byte character set (Chinese dialects, Japanese and Korean).
var dbcs []string = []string{
	"zh-HK",
	"zh-MO",
	"zh-CN",
	"zh-SG",
	"zh-TW",
	"ja-JP",
	"ko-KR",
}

// IsDBCS returns if a workbook's default language is among DBCS.
func (e *evalContext) IsDBCS() bool {
	language := e.s.w.CoreProperties.X().Language
	if language == nil {
		return false
	}
	defaultLanguage := string(language.Data)
	for _, lang := range dbcs {
		if defaultLanguage == lang {
			return true
		}
	}
	return false
}

// LastColumn returns the name of last column which contains data in range of context sheet's given rows.
func (e *evalContext) LastColumn(rowFrom, rowTo int) string {
	sheet := e.s
	max := 1
	for row := rowFrom; row <= rowTo; row++ {
		l := len(sheet.Row(uint32(row)).Cells())
		if l > max {
			max = l
		}
	}
	return reference.IndexToColumn(uint32(max-1))
}

// LastRow returns the name of last row which contains data in range of context sheet's given columns.
func (e *evalContext) LastRow(col string) int {
	sheet := e.s
	colIdx := int(reference.ColumnToIndex(col))
	max := 1
	for _, r := range sheet.x.SheetData.Row {
		if r.RAttr != nil {
			row := Row{sheet.w, sheet.x, r}
			l := len(row.Cells())
			if l > colIdx {
				max = int(row.RowNumber())
			}
		}
	}
	return max
}

var refRegexp *regexp.Regexp = regexp.MustCompile(`^([a-z]+)([0-9]+)$`)

func validateRef(cr string) bool {
	if submatch := refRegexp.FindStringSubmatch(strings.ToLower(cr)); len(submatch) > 2 {
		col := submatch[1]
		row, err := strconv.Atoi(submatch[2])
		if err != nil { // for the case if the row number is bigger then int capacity
			return false
		}
		return row <= 1048576 && col <= "zz"
	}
	return false
}