add config package

1 files changed, 127 insertions, 0 deletions

diff --git a/config/config.go b/config/config.go
new file mode 100644
index 0000000..3a5920c
--- /dev/null
+++ b/config/config.go
@@ -0,0 +1,127 @@
+// 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
+}