package ods

import (
	"archive/zip"
	"bytes"
	"encoding/xml"
	"fmt"
	"strconv"
	"strings"
	"time"
)

// Write produces an ODS file as []byte from a Workbook.
func Write(wb *Workbook) ([]byte, error) {
	var buf bytes.Buffer
	zw := zip.NewWriter(&buf)

	// mimetype MUST be first entry, stored (not compressed)
	mimeHeader := &zip.FileHeader{
		Name:   "mimetype",
		Method: zip.Store,
	}
	mw, err := zw.CreateHeader(mimeHeader)
	if err != nil {
		return nil, fmt.Errorf("create mimetype: %w", err)
	}
	if _, err := mw.Write([]byte("application/vnd.oasis.opendocument.spreadsheet")); err != nil {
		return nil, fmt.Errorf("write mimetype: %w", err)
	}

	// META-INF/manifest.xml
	if err := writeManifest(zw); err != nil {
		return nil, err
	}

	// meta.xml
	if err := writeMeta(zw, wb.Meta); err != nil {
		return nil, err
	}

	// styles.xml
	if err := writeStyles(zw); err != nil {
		return nil, err
	}

	// content.xml
	if err := writeContent(zw, wb.Sheets); err != nil {
		return nil, err
	}

	if err := zw.Close(); err != nil {
		return nil, fmt.Errorf("close zip: %w", err)
	}
	return buf.Bytes(), nil
}

// writeManifest writes META-INF/manifest.xml.
func writeManifest(zw *zip.Writer) error {
	w, err := zw.Create("META-INF/manifest.xml")
	if err != nil {
		return fmt.Errorf("create manifest: %w", err)
	}
	const manifest = xml.Header + `<manifest:manifest xmlns:manifest="urn:oasis:names:tc:opendocument:xmlns:manifest:1.0" manifest:version="1.2">
 <manifest:file-entry manifest:media-type="application/vnd.oasis.opendocument.spreadsheet" manifest:version="1.2" manifest:full-path="/"/>
 <manifest:file-entry manifest:media-type="text/xml" manifest:full-path="content.xml"/>
 <manifest:file-entry manifest:media-type="text/xml" manifest:full-path="styles.xml"/>
 <manifest:file-entry manifest:media-type="text/xml" manifest:full-path="meta.xml"/>
</manifest:manifest>`
	_, err = w.Write([]byte(manifest))
	return err
}

// writeMeta writes meta.xml with custom properties.
func writeMeta(zw *zip.Writer, meta map[string]string) error {
	w, err := zw.Create("meta.xml")
	if err != nil {
		return fmt.Errorf("create meta.xml: %w", err)
	}

	var b strings.Builder
	b.WriteString(xml.Header)
	b.WriteString(`<office:document-meta xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0"`)
	b.WriteString(` xmlns:meta="urn:oasis:names:tc:opendocument:xmlns:meta:1.0"`)
	b.WriteString(` office:version="1.2">`)
	b.WriteString(`<office:meta>`)
	b.WriteString(`<meta:generator>Silo</meta:generator>`)
	b.WriteString(fmt.Sprintf(`<meta:creation-date>%s</meta:creation-date>`, time.Now().UTC().Format(time.RFC3339)))

	if len(meta) > 0 {
		b.WriteString(`<meta:user-defined meta:name="_silo_meta" meta:value-type="string">`)
		// Encode all meta as key=value pairs separated by newlines
		var pairs []string
		for k, v := range meta {
			pairs = append(pairs, xmlEscape(k)+"="+xmlEscape(v))
		}
		b.WriteString(xmlEscape(strings.Join(pairs, "\n")))
		b.WriteString(`</meta:user-defined>`)
	}

	b.WriteString(`</office:meta>`)
	b.WriteString(`</office:document-meta>`)

	_, err = w.Write([]byte(b.String()))
	return err
}

// writeStyles writes styles.xml with header, currency, and hidden column styles.
func writeStyles(zw *zip.Writer) error {
	w, err := zw.Create("styles.xml")
	if err != nil {
		return fmt.Errorf("create styles.xml: %w", err)
	}

	const styles = xml.Header + `<office:document-styles
 xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0"
 xmlns:style="urn:oasis:names:tc:opendocument:xmlns:style:1.0"
 xmlns:fo="urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0"
 xmlns:number="urn:oasis:names:tc:opendocument:xmlns:datastyle:1.0"
 xmlns:table="urn:oasis:names:tc:opendocument:xmlns:table:1.0"
 office:version="1.2">
</office:document-styles>`

	_, err = w.Write([]byte(styles))
	return err
}

// writeContent writes content.xml containing all sheet data.
func writeContent(zw *zip.Writer, sheets []Sheet) error {
	w, err := zw.Create("content.xml")
	if err != nil {
		return fmt.Errorf("create content.xml: %w", err)
	}

	var b strings.Builder
	b.WriteString(xml.Header)
	b.WriteString(`<office:document-content`)
	b.WriteString(` xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0"`)
	b.WriteString(` xmlns:style="urn:oasis:names:tc:opendocument:xmlns:style:1.0"`)
	b.WriteString(` xmlns:text="urn:oasis:names:tc:opendocument:xmlns:text:1.0"`)
	b.WriteString(` xmlns:table="urn:oasis:names:tc:opendocument:xmlns:table:1.0"`)
	b.WriteString(` xmlns:fo="urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0"`)
	b.WriteString(` xmlns:number="urn:oasis:names:tc:opendocument:xmlns:datastyle:1.0"`)
	b.WriteString(` xmlns:of="urn:oasis:names:tc:opendocument:xmlns:of:1.2"`)
	b.WriteString(` office:version="1.2">`)

	// Automatic styles (defined in content.xml for cell/column styles)
	b.WriteString(`<office:automatic-styles>`)

	// Currency data style
	b.WriteString(`<number:currency-style style:name="N-USD" number:language="en" number:country="US">`)
	b.WriteString(`<number:currency-symbol number:language="en" number:country="US">$</number:currency-symbol>`)
	b.WriteString(`<number:number number:decimal-places="2" number:min-decimal-places="2" number:min-integer-digits="1" number:grouping="true"/>`)
	b.WriteString(`</number:currency-style>`)

	// Header cell style (bold)
	b.WriteString(`<style:style style:name="ce-header" style:family="table-cell">`)
	b.WriteString(`<style:text-properties fo:font-weight="bold"/>`)
	b.WriteString(`<style:table-cell-properties fo:background-color="#d9e2f3"/>`)
	b.WriteString(`</style:style>`)

	// Currency cell style
	b.WriteString(`<style:style style:name="ce-currency" style:family="table-cell" style:data-style-name="N-USD">`)
	b.WriteString(`</style:style>`)

	// Row status colors
	writeColorStyle(&b, "ce-synced", "#c6efce")
	writeColorStyle(&b, "ce-modified", "#ffeb9c")
	writeColorStyle(&b, "ce-new", "#bdd7ee")
	writeColorStyle(&b, "ce-error", "#ffc7ce")
	writeColorStyle(&b, "ce-conflict", "#f4b084")

	// Column styles
	b.WriteString(`<style:style style:name="co-default" style:family="table-column">`)
	b.WriteString(`<style:table-column-properties style:column-width="2.5cm"/>`)
	b.WriteString(`</style:style>`)

	b.WriteString(`<style:style style:name="co-wide" style:family="table-column">`)
	b.WriteString(`<style:table-column-properties style:column-width="5cm"/>`)
	b.WriteString(`</style:style>`)

	b.WriteString(`<style:style style:name="co-hidden" style:family="table-column">`)
	b.WriteString(`<style:table-column-properties style:column-width="2.5cm"/>`)
	b.WriteString(`</style:style>`)

	b.WriteString(`</office:automatic-styles>`)

	// Body
	b.WriteString(`<office:body>`)
	b.WriteString(`<office:spreadsheet>`)

	for _, sheet := range sheets {
		writeSheet(&b, &sheet)
	}

	b.WriteString(`</office:spreadsheet>`)
	b.WriteString(`</office:body>`)
	b.WriteString(`</office:document-content>`)

	_, err = w.Write([]byte(b.String()))
	return err
}

func writeColorStyle(b *strings.Builder, name, color string) {
	b.WriteString(fmt.Sprintf(`<style:style style:name="%s" style:family="table-cell">`, name))
	b.WriteString(fmt.Sprintf(`<style:table-cell-properties fo:background-color="%s"/>`, color))
	b.WriteString(`</style:style>`)
}

func writeSheet(b *strings.Builder, sheet *Sheet) {
	b.WriteString(fmt.Sprintf(`<table:table table:name="%s">`, xmlEscape(sheet.Name)))

	// Column definitions
	if len(sheet.Columns) > 0 {
		for _, col := range sheet.Columns {
			styleName := "co-default"
			if col.Width != "" {
				styleName = "co-wide"
			}
			if col.Hidden {
				b.WriteString(fmt.Sprintf(`<table:table-column table:style-name="%s" table:visibility="collapse"/>`, styleName))
			} else {
				b.WriteString(fmt.Sprintf(`<table:table-column table:style-name="%s"/>`, styleName))
			}
		}
	}

	// Rows
	for _, row := range sheet.Rows {
		if row.IsBlank {
			b.WriteString(`<table:table-row>`)
			b.WriteString(`<table:table-cell/>`)
			b.WriteString(`</table:table-row>`)
			continue
		}

		b.WriteString(`<table:table-row>`)
		for _, cell := range row.Cells {
			writeCell(b, &cell)
		}
		b.WriteString(`</table:table-row>`)
	}

	b.WriteString(`</table:table>`)
}

func writeCell(b *strings.Builder, cell *Cell) {
	switch cell.Type {
	case CellEmpty:
		b.WriteString(`<table:table-cell/>`)

	case CellFormula:
		// Formula cells: the formula attribute uses the of: namespace
		b.WriteString(fmt.Sprintf(`<table:table-cell table:formula="%s" office:value-type="float" table:style-name="ce-currency">`, xmlEscape(cell.Formula)))
		b.WriteString(`</table:table-cell>`)

	case CellFloat:
		b.WriteString(fmt.Sprintf(`<table:table-cell office:value-type="float" office:value="%s">`, xmlEscape(cell.Value)))
		b.WriteString(fmt.Sprintf(`<text:p>%s</text:p>`, xmlEscape(cell.Value)))
		b.WriteString(`</table:table-cell>`)

	case CellCurrency:
		b.WriteString(fmt.Sprintf(`<table:table-cell office:value-type="currency" office:currency="USD" office:value="%s" table:style-name="ce-currency">`, xmlEscape(cell.Value)))
		b.WriteString(fmt.Sprintf(`<text:p>$%s</text:p>`, xmlEscape(cell.Value)))
		b.WriteString(`</table:table-cell>`)

	case CellDate:
		b.WriteString(fmt.Sprintf(`<table:table-cell office:value-type="date" office:date-value="%s">`, xmlEscape(cell.Value)))
		b.WriteString(fmt.Sprintf(`<text:p>%s</text:p>`, xmlEscape(cell.Value)))
		b.WriteString(`</table:table-cell>`)

	default: // CellString
		b.WriteString(`<table:table-cell office:value-type="string">`)
		b.WriteString(fmt.Sprintf(`<text:p>%s</text:p>`, xmlEscape(cell.Value)))
		b.WriteString(`</table:table-cell>`)
	}
}

// xmlEscape escapes special XML characters.
func xmlEscape(s string) string {
	var b strings.Builder
	if err := xml.EscapeText(&b, []byte(s)); err != nil {
		return s
	}
	return b.String()
}

// Helper functions for building cells

// StringCell creates a string cell.
func StringCell(value string) Cell {
	return Cell{Value: value, Type: CellString}
}

// FloatCell creates a float cell.
func FloatCell(value float64) Cell {
	return Cell{Value: strconv.FormatFloat(value, 'f', -1, 64), Type: CellFloat}
}

// CurrencyCell creates a currency (USD) cell.
func CurrencyCell(value float64) Cell {
	return Cell{Value: fmt.Sprintf("%.2f", value), Type: CellCurrency}
}

// FormulaCell creates a formula cell.
func FormulaCell(formula string) Cell {
	return Cell{Formula: formula, Type: CellFormula}
}

// EmptyCell creates an empty cell.
func EmptyCell() Cell {
	return Cell{Type: CellEmpty}
}

// IntCell creates an integer cell stored as float.
func IntCell(value int) Cell {
	return Cell{Value: strconv.Itoa(value), Type: CellFloat}
}

// HeaderCell creates a string cell intended for header rows.
// The header style is applied at the row level or by the caller.
func HeaderCell(value string) Cell {
	return Cell{Value: value, Type: CellString}
}