package sqlmock

import (
	"database/sql/driver"
	"encoding/csv"
	"fmt"
	"io"
	"strings"
)

// CSVColumnParser is a function which converts trimmed csv
// column string to a []byte representation. currently
// transforms NULL to nil
var CSVColumnParser = func(s string) []byte {
	switch {
	case strings.ToLower(s) == "null":
		return nil
	}
	return []byte(s)
}

type rowSets struct {
	sets []*Rows
	pos  int
}

func (rs *rowSets) Columns() []string {
	return rs.sets[rs.pos].cols
}

func (rs *rowSets) Close() error {
	return rs.sets[rs.pos].closeErr
}

// advances to next row
func (rs *rowSets) Next(dest []driver.Value) error {
	r := rs.sets[rs.pos]
	r.pos++
	if r.pos > len(r.rows) {
		return io.EOF // per interface spec
	}

	for i, col := range r.rows[r.pos-1] {
		dest[i] = col
	}

	return r.nextErr[r.pos-1]
}

// transforms to debuggable printable string
func (rs *rowSets) String() string {
	msg := "should return rows:\n"
	if len(rs.sets) == 1 {
		for n, row := range rs.sets[0].rows {
			msg += fmt.Sprintf("    row %d - %+v\n", n, row)
		}
		return strings.TrimSpace(msg)
	}
	for i, set := range rs.sets {
		msg += fmt.Sprintf("    result set: %d\n", i)
		for n, row := range set.rows {
			msg += fmt.Sprintf("      row %d - %+v\n", n, row)
		}
	}
	return strings.TrimSpace(msg)
}

// Rows is a mocked collection of rows to
// return for Query result
type Rows struct {
	cols     []string
	rows     [][]driver.Value
	pos      int
	nextErr  map[int]error
	closeErr error
}

// NewRows allows Rows to be created from a
// sql driver.Value slice or from the CSV string and
// to be used as sql driver.Rows
func NewRows(columns []string) *Rows {
	return &Rows{cols: columns, nextErr: make(map[int]error)}
}

// CloseError allows to set an error
// which will be returned by rows.Close
// function.
//
// The close error will be triggered only in cases
// when rows.Next() EOF was not yet reached, that is
// a default sql library behavior
func (r *Rows) CloseError(err error) *Rows {
	r.closeErr = err
	return r
}

// RowError allows to set an error
// which will be returned when a given
// row number is read
func (r *Rows) RowError(row int, err error) *Rows {
	r.nextErr[row] = err
	return r
}

// AddRow composed from database driver.Value slice
// return the same instance to perform subsequent actions.
// Note that the number of values must match the number
// of columns
func (r *Rows) AddRow(values ...driver.Value) *Rows {
	if len(values) != len(r.cols) {
		panic("Expected number of values to match number of columns")
	}

	row := make([]driver.Value, len(r.cols))
	for i, v := range values {
		row[i] = v
	}

	r.rows = append(r.rows, row)
	return r
}

// FromCSVString build rows from csv string.
// return the same instance to perform subsequent actions.
// Note that the number of values must match the number
// of columns
func (r *Rows) FromCSVString(s string) *Rows {
	res := strings.NewReader(strings.TrimSpace(s))
	csvReader := csv.NewReader(res)

	for {
		res, err := csvReader.Read()
		if err != nil || res == nil {
			break
		}

		row := make([]driver.Value, len(r.cols))
		for i, v := range res {
			row[i] = CSVColumnParser(strings.TrimSpace(v))
		}
		r.rows = append(r.rows, row)
	}
	return r
}
