// SPDX-License-Identifier: ISC
// Copyright © 2021 siddharth <s@ricketyspace.net>

package config

import (
	"encoding/json"
	"fmt"
	"os"
	"path"
	"strings"

	"ricketyspace.net/fern/file"
)

type Feed struct {
	Id     string `json:"id"`
	Source string `json:"source"`
	Schema string `json:"schema"`
}

type FernConfig struct {
	YDLPath string `json:"ydl-path"`
	DumpDir string `json:"dump-dir"`
	Feeds   []Feed `json:"feeds"`
}

func Read() (*FernConfig, error) {
	// Construct config file path.
	h, err := os.UserHomeDir()
	if err != nil {
		return nil, err
	}
	c := path.Join(h, ".config", "fern", "fern.json")

	// Open config file.
	f, err := os.Open(c)
	if err != nil {
		return nil, err
	}

	// Read config file.
	bs, err := file.Read(f)
	if err != nil {
		return nil, err
	}

	// Unmarshal config into an object.
	config := new(FernConfig)
	err = json.Unmarshal(bs, config)
	if err != nil {
		return nil, err
	}

	// Validate config.
	err = config.validate()
	if err != nil {
		return nil, err
	}
	return config, nil
}

func (config *FernConfig) validate() error {
	// Validate 'ydl-path' in config.
	if len(config.YDLPath) == 0 {
		return fmt.Errorf("'ydl-path' not set in config")
	}
	_, err := os.Stat(config.YDLPath)
	if err != nil {
		return err
	}

	// Validate 'dump-dir' in config.
	if len(config.DumpDir) == 0 {
		return fmt.Errorf("'dump-dir' not set in config")
	}
	// Replace "~" with user's home directory in the dump
	// directory path.
	h, err := os.UserHomeDir()
	if err != nil {
		return err
	}
	config.DumpDir = strings.Replace(config.DumpDir, "~", h, 1)
	// Ensure dump directory exists.
	err = os.MkdirAll(config.DumpDir, 0755)
	if err != nil {
		return err
	}

	// Validate 'feeds' in config.
	if len(config.Feeds) == 0 {
		return fmt.Errorf("'feeds' not set in config")
	}
	for _, feed := range config.Feeds {
		err = feed.validate()
		if err != nil {
			return err
		}
	}
	return nil

}

func (feed *Feed) validate() error {
	// Check 'id'
	if len(feed.Id) == 0 {
		return fmt.Errorf("'id' not set in a feed")
	}

	// Check 'source'
	if len(feed.Source) == 0 {
		return fmt.Errorf("'source' not set in a feed '%s'", feed.Id)
	}

	// Check 'schema'
	schemaOK := false
	for _, schema := range []string{"npr", "youtube"} {
		if feed.Schema == schema {
			schemaOK = true
		}
	}
	if !schemaOK {
		return fmt.Errorf("schema '%s' for feed '%s' is not valid",
			feed.Schema, feed.Id)
	}
	return nil
}