/*
Copyright © 2022-2025 Thomas von Dein

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

package lib

import (
	"bufio"
	"encoding/csv"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"math"
	"regexp"
	"strings"

	"github.com/alecthomas/repr"
	"github.com/tlinden/tablizer/cfg"
)

/*
Parser switch
*/
func Parse(conf cfg.Config, input io.Reader) (Tabdata, error) {
	var data Tabdata
	var err error

	// first step, parse the data
	if len(conf.Separator) == 1 {
		data, err = parseCSV(conf, input)
	} else if conf.InputJSON {
		data, err = parseJSON(conf, input)
	} else {
		data, err = parseTabular(conf, input)
	}

	if err != nil {
		return data, err
	}

	// 2nd step, apply filters, code or transposers, if any
	postdata, changed, err := PostProcess(conf, &data)
	if err != nil {
		return data, err
	}

	if changed {
		return *postdata, nil
	}

	return data, err
}

/*
Parse CSV input.
*/
func parseCSV(conf cfg.Config, input io.Reader) (Tabdata, error) {
	data := Tabdata{}

	// apply pattern, if any
	content, err := FilterByPattern(conf, input)
	if err != nil {
		return data, err
	}

	csvreader := csv.NewReader(content)
	csvreader.Comma = rune(conf.Separator[0])

	records, err := csvreader.ReadAll()
	if err != nil {
		return data, fmt.Errorf("could not parse CSV input: %w", err)
	}

	if len(records) >= 1 {
		data.headers = records[0]
		data.columns = len(records)

		for _, head := range data.headers {
			// register widest header field
			headerlen := len(head)
			if headerlen > data.maxwidthHeader {
				data.maxwidthHeader = headerlen
			}
		}

		if len(records) > 1 {
			data.entries = records[1:]
		}
	}

	return data, nil
}

/*
Parse tabular input.
*/
func parseTabular(conf cfg.Config, input io.Reader) (Tabdata, error) {
	data := Tabdata{}

	var scanner *bufio.Scanner

	hadFirst := false
	separate := regexp.MustCompile(conf.Separator)

	scanner = bufio.NewScanner(input)

	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		parts := separate.Split(line, -1)

		if !hadFirst {
			// header processing
			data.columns = len(parts)

			// process all header fields
			for _, part := range parts {
				// register widest header field
				headerlen := len(part)
				if headerlen > data.maxwidthHeader {
					data.maxwidthHeader = headerlen
				}

				// register fields data
				data.headers = append(data.headers, strings.TrimSpace(part))

				// done
				hadFirst = true
			}
		} else {
			// data processing
			if matchPattern(conf, line) == conf.InvertMatch {
				// by default  -v is false, so if a  line does NOT
				// match the pattern, we will ignore it. However,
				// if the user specified -v, the matching is inverted,
				// so we ignore all lines, which DO match.
				continue
			}

			idx := 0 // we cannot use the header index, because we could exclude columns
			values := []string{}
			for _, part := range parts {
				// if Debug {
				// 	fmt.Printf("<%s> ", value)
				// }
				values = append(values, strings.TrimSpace(part))

				idx++
			}

			// fill up missing fields, if any
			for i := len(values); i < len(data.headers); i++ {
				values = append(values, "")
			}

			data.entries = append(data.entries, values)
		}
	}

	if scanner.Err() != nil {
		return data, fmt.Errorf("failed to read from io.Reader: %w", scanner.Err())
	}

	return data, nil
}

/*
Parse JSON input.  We only support an array of  maps.
*/
func parseRawJSON(conf cfg.Config, input io.Reader) (Tabdata, error) {
	dec := json.NewDecoder(input)
	headers := []string{}
	idxmap := map[string]int{}
	data := [][]string{}
	row := []string{}
	iskey := true
	haveheaders := false
	var currentfield string
	var idx int
	var isjson bool

	for {
		t, err := dec.Token()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatal(err)
		}

		switch val := t.(type) {
		case string:
			if iskey {
				if !haveheaders {
					// consider only the keys of the first item as headers
					headers = append(headers, val)
				}
				currentfield = val
			} else {
				if !haveheaders {
					// the first row uses the order as it comes in
					row = append(row, val)
				} else {
					// use  the pre-determined  order, that  way items
					// can be in any order as long as they contain all
					// neccessary  fields. They may also  contain less
					// fields than the  first item, these will contain
					// the empty string
					row[idxmap[currentfield]] = val
				}
			}

		case float64:
			var value string

			// we set precision to 0 if the float is a whole number
			if val == math.Trunc(val) {
				value = fmt.Sprintf("%.f", val)
			} else {
				value = fmt.Sprintf("%f", val)
			}

			if !haveheaders {
				row = append(row, value)
			} else {
				row[idxmap[currentfield]] = value
			}

		case nil:
			// we ignore here if a value  shall be an int or a string,
			// because tablizer only works with strings anyway
			if !haveheaders {
				row = append(row, "")
			} else {
				row[idxmap[currentfield]] = ""
			}

		case json.Delim:
			if val.String() == "}" {
				data = append(data, row)
				row = make([]string, len(headers))
				idx++

				if !haveheaders {
					// remember  the array position of  header fields,
					// which we use to  assign elements to the correct
					// row index
					for i, header := range headers {
						idxmap[header] = i
					}
				}

				haveheaders = true
			}
			isjson = true
		default:
			fmt.Printf("unknown token: %v type: %T\n", t, t)
		}

		iskey = !iskey
	}

	if isjson && (len(headers) == 0 || len(data) == 0) {
		return Tabdata{}, errors.New("failed to parse JSON, input did not contain array of hashes")
	}

	return Tabdata{headers: headers, entries: data, columns: len(headers)}, nil
}

func parseJSON(conf cfg.Config, input io.Reader) (Tabdata, error) {
	// parse raw json
	data, err := parseRawJSON(conf, input)
	if err != nil {
		return data, err
	}

	// apply filter, if any
	filtered := [][]string{}
	var line string

	for _, row := range data.entries {
		line = strings.Join(row, " ")

		if matchPattern(conf, line) == conf.InvertMatch {
			continue
		}

		filtered = append(filtered, row)
	}

	if len(filtered) != len(data.entries) {
		data.entries = filtered
	}

	return data, nil
}

func PostProcess(conf cfg.Config, data *Tabdata) (*Tabdata, bool, error) {
	var modified bool

	// filter by field filters, if any
	filtereddata, changed, err := FilterByFields(conf, data)
	if err != nil {
		return data, false, fmt.Errorf("failed to filter fields: %w", err)
	}

	if changed {
		data = filtereddata
		modified = true
	}

	// check if transposers are valid and turn into Transposer structs
	if err := PrepareTransposerColumns(&conf, data); err != nil {
		return data, false, err
	}

	// transpose if demanded
	modifieddata, changed, err := TransposeFields(conf, data)
	if err != nil {
		return data, false, fmt.Errorf("failed to transpose fields: %w", err)
	}

	if changed {
		data = modifieddata
		modified = true
	}

	if conf.Debug {
		repr.Print(data)
	}

	return data, modified, nil
}