package changelog

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"strings"
)

// LoadPeople reads people.json, a map from address to display name.
// Addresses are matched case-insensitively.
func LoadPeople(path string) (People, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	var m map[string]string
	if err := json.Unmarshal(raw, &m); err != nil {
		return nil, fmt.Errorf("%s: %w", path, err)
	}
	p := People{}
	for k, v := range m {
		if k == "//" {
			continue
		}
		p[strings.ToLower(k)] = v
	}
	return p, nil
}

// LoadLinks reads changelog-links.json. A missing file is no links.
func LoadLinks(path string) (Links, error) {
	raw, err := os.ReadFile(path)
	if errors.Is(err, fs.ErrNotExist) {
		return Links{}, nil
	}
	if err != nil {
		return nil, err
	}
	var m map[string]json.RawMessage
	if err := json.Unmarshal(raw, &m); err != nil {
		return nil, fmt.Errorf("%s: %w", path, err)
	}
	l := Links{}
	for tag, v := range m {
		if tag == "//" {
			continue
		}
		var byLead map[string][]string
		if err := json.Unmarshal(v, &byLead); err != nil {
			return nil, fmt.Errorf("%s: %s: %w", path, tag, err)
		}
		l[tag] = byLead
	}
	return l, nil
}

// Load reads a committed changelog.json.
func Load(path string) (*Changelog, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	var c Changelog
	dec := json.NewDecoder(bytes.NewReader(raw))
	dec.DisallowUnknownFields()
	if err := dec.Decode(&c); err != nil {
		return nil, fmt.Errorf("%s: %w", path, err)
	}
	return &c, nil
}

// Marshal is the committed form: indented, no HTML escaping (the notes
// carry "<app>" placeholders), and a trailing newline.
func Marshal(c *Changelog) ([]byte, error) {
	var b bytes.Buffer
	enc := json.NewEncoder(&b)
	enc.SetEscapeHTML(false)
	enc.SetIndent("", "  ")
	if err := enc.Encode(c); err != nil {
		return nil, err
	}
	return b.Bytes(), nil
}