package storefile

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"

	eenc "git.keganmyers.com/terribleplan/file-store/pkg/erasureencode"
)

func StoreFile(inputPath, outputPath string, size int32, shards, parity uint16, name string) error {
	if size <= 0 {
		return fmt.Errorf("size must be greater than 0")
	}

	// fmt.Printf("starting...\n")
	inputPath, err := filepath.Abs(inputPath)
	if err != nil {
		return err
	}

	inputFile, err := os.Open(inputPath)
	if err != nil {
		return err
	}
	defer inputFile.Close()

	if err := os.MkdirAll(outputPath, 0755); err != nil {
		return err
	}

	if dirents, err := os.ReadDir(outputPath); err != nil {
		return err
	} else if len(dirents) > 0 {
		return fmt.Errorf("expected output dir to be empty")
	}

	outputFileCount := shards + parity
	outputFiles := make([]*os.File, outputFileCount)
	for i := uint16(0); i < outputFileCount; i++ {
		outputFile, err := os.OpenFile(filepath.Join(outputPath, fmt.Sprintf("shard.%04d", i+1)), os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
		if err != nil {
			return err
		}
		defer outputFile.Close()
		outputFiles[i] = outputFile
	}

	outputs := make([]io.Writer, outputFileCount)
	for i, f := range outputFiles {
		outputs[i] = f
	}

	// fmt.Printf("writing shards...\n")
	meta, err := eenc.EncodeFile(inputFile, outputs, size, shards, parity)
	if err != nil {
		return err
	}

	meta.Name = name
	if meta.Name == "" {
		meta.Name = filepath.Base(inputPath)
	}

	// fmt.Printf("writing meta...\n")
	metaFile, err := os.OpenFile(filepath.Join(outputPath, "meta.json"), os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
	if err != nil {
		return err
	}
	defer metaFile.Close()

	enc := json.NewEncoder(metaFile)
	if err := enc.Encode(meta); err != nil {
		return err
	}

	if err := metaFile.Sync(); err != nil {
		return err
	}

	// fmt.Printf("done...\n")
	return nil
}

func ReadFile(inputPath, outputPath string, overwrite bool) error {
	inputAbs, err := filepath.Abs(inputPath)
	if err != nil {
		panic(err)
		return err
	}

	metaFile, err := os.OpenFile(filepath.Join(inputAbs, "meta.json"), os.O_RDONLY, 0644)
	if err != nil {
		panic(err)
		return err
	}
	defer metaFile.Close()

	meta := &eenc.EEMeta{}
	dec := json.NewDecoder(metaFile)
	if err := dec.Decode(meta); err != nil {
		panic(err)
		return err
	}

	// fmt.Printf("%#v", *meta)

	if outputPath == "" {
		outputPath = meta.Name
	}

	outputFlags := os.O_WRONLY
	if overwrite {
		outputFlags |= os.O_CREATE | os.O_TRUNC
	} else {
		outputFlags |= os.O_CREATE | os.O_EXCL
	}
	outputAbs, err := filepath.Abs(outputPath)
	if err != nil {
		panic(err)
		return err
	}
	outputFile, err := os.OpenFile(outputAbs, outputFlags, 0644)
	if err != nil {
		panic(err)
		return err
	}

	inputFiles := make([]*os.File, meta.Params.Shards)
	for i := uint16(0); i < meta.Params.Shards; i++ {
		inputFile, err := os.OpenFile(filepath.Join(inputPath, fmt.Sprintf("shard.%04d", i+1)), os.O_RDONLY, 0644)
		if err != nil {
			panic(err)
			return err
		}
		defer inputFile.Close()
		inputFiles[i] = inputFile
	}

	inputs := make([]io.ReadSeeker, meta.Params.Shards)
	for i, f := range inputFiles {
		inputs[i] = f
	}

	if err := eenc.Decode(inputs, outputFile, meta); err != nil {
		panic(err)
		return err
	}

	return nil
}