➜  hugo-playground git:(main) git checkout 01-config
Switched to branch '01-config'
Your branch is up to date with 'origin/01-config'.
➜  hugo-playground git:(01-config) 

➜  hugo-playground git:(01-config) tree
.
├── LICENSE
├── README.md
├── command.sh
├── common
│    ├── maps
│    │    ├── maps.go
│    │    └── params.go
│    └── paths
│         └── path.go
├── config
│    ├── commonConfig.go
│    ├── compositeConfig.go
│    ├── configLoader.go
│    ├── configProvider.go
│    ├── defaultConfigProvider.go
│    └── env.go
├── go.mod
├── go.sum
├── hugo-playground
├── hugofs
│    ├── files
│    │    └── classifier.go
│    └── fs.go
├── hugolib
│    └── config.go
├── langs
│    ├── config.go
│    └── language.go
├── log
│    └── logger.go
├── main.go
├── modules
│    ├── client.go
│    ├── collect.go
│    ├── config.go
│    └── module.go
├── parser
│    └── metadecoders
│         ├── decoder.go
│         └── format.go
└── types
    ├── convert.go
    └── types.go

13 directories, 30 files

...
    // 1. config
	log.Process("main", "load configurations from config.toml and themes")
	cfg, _, err := hugolib.LoadConfig(
		hugolib.ConfigSourceDescriptor{
			WorkingDir: tempDir,
			Fs:         afs,
			Filename:   "config.toml",
		},
	)
	fmt.Printf("%#v\n", cfg)

go run .

package main

import (
	"bytes"
	"fmt"
	toml "github.com/pelletier/go-toml/v2"
	"golang.org/x/tools/txtar"
	"path/filepath"
	"strings"
)

// 文件结构
// 文件名: config.toml
// 文件内容：theme = 'mytheme'
var files = "-- config.toml --\n" +
	"theme = 'mytheme'"

// Format 文件格式类型
type Format string

// TOML 支持的格式，为简单示例，只支持TOML格式
const (
	TOML Format = "toml"
)

func main() {
	// 解析上面的文件结构
	data := txtar.Parse([]byte(files))
	fmt.Println("File start:")

	// Input: 数据，格式，输出类型
	var configData []byte
	var format Format
	m := make(map[string]any)

	// 遍历解析生成的所有文件，通过File结构体获取文件名和文件数据
	// f.Name 获取文件名
	// f.Data 获取文件数据
	// 如果是config.toml文件，则获取文件数据
	for _, f := range data.Files {
		if "config.toml" == f.Name {
			configData = bytes.TrimSuffix(
				f.Data, []byte("\n"))
			format = FormatFromString(f.Name)
		}
	}

	err := UnmarshalTo(configData, format, &m)
	if err != nil {
		fmt.Println(err)
	} else {
		fmt.Println(m)
	}

	fmt.Println("File end.")
}

// FormatFromString turns formatStr, typically a file extension without any ".",
// into a Format. It returns an empty string for unknown formats.
// Hugo 实现
func FormatFromString(formatStr string) Format {
	formatStr = strings.ToLower(formatStr)
	if strings.Contains(formatStr, ".") {
		// Assume a filename
		formatStr = strings.TrimPrefix(
			filepath.Ext(formatStr), ".")
	}
	switch formatStr {
	case "toml":
		return TOML
	}

	return ""
}

// UnmarshalTo unmarshals data in format f into v.
func UnmarshalTo(data []byte, f Format, v any) error {
	var err error

	switch f {
	case TOML:
		err = toml.Unmarshal(data, v)

	default:
		return fmt.Errorf(
			"unmarshal of format %q is not supported", f)
	}

	if err == nil {
		return nil
	}

	return err
}

# 解析后得到文件config.toml
# 准备Input：config file data, format, map[string]any
# 得到Output: map[theme:mytheme]
File start:
map[theme:mytheme]
File end.

Program exited.

// hugo-playground/hugolib/config.go
// line 54
func (l configLoader) applyConfigDefaults() error {
	defaultSettings := maps.Params{
		...
		"timeout":                              "30s",
		...
	}

	l.cfg.SetDefaults(defaultSettings)

	return nil
}

// hugo-playground/config/defaultConfigProvider.go
// line 16
// New creates a Provider backed by an empty maps.Params.
func New() Provider {
	return &defaultConfigProvider{
		root: make(maps.Params),
	}
}

// hugo-playground/config/configProvider.go
// line 9
// Provider provides the configuration settings for Hugo.
type Provider interface {
	...
	Get(key string) any
	Set(key string, value any)
	SetDefaults(params maps.Params)
	...
}

// hugo-playground/common/maps/params.go
// line 9
// Params is a map where all keys are lower case.
type Params map[string]any

package main

import (
	"fmt"
	"reflect"
	"strings"
)

// Provider 定义提供方需要具备的能力
// 通过Key查询值
// 设置键值对
// 设置默认参数
type Provider interface {
	Get(key string) any
	Set(key string, value any)
	SetDefaults(params Params)
}

// Params 参数格式定义
// 关键字为字符类型
// 值为通用类型any
type Params map[string]any

// Set 根据新传入参数，对应层级进行重写
// pp为新传入参数
// p为当前参数
// 将pp的值按层级结构写入p
// 递归完成
func (p Params) Set(pp Params) {
	for k, v := range pp {
		vv, found := p[k]
		if !found {
			p[k] = v
		} else {
			switch vvv := vv.(type) {
			case Params:
				if pv, ok := v.(Params); ok {
					vvv.Set(pv)
				} else {
					p[k] = v
				}
			default:
				p[k] = v
			}
		}
	}
}

func New() Provider {
	return &defaultConfigProvider{
		root: make(Params),
	}
}

// defaultConfigProvider Provider接口实现对象
type defaultConfigProvider struct {
	root Params
}

// Get 按key获取值
// 约定""键对应的是c.root
// 嵌套获取值
func (c *defaultConfigProvider) Get(k string) any {
	if k == "" {
		return c.root
	}
	key, m := c.getNestedKeyAndMap(strings.ToLower(k))
	if m == nil {
		return nil
	}
	v := m[key]
	return v
}

// getNestedKeyAndMap 支持多级查询
// 通过分隔符"."获取查询路径
func (c *defaultConfigProvider) getNestedKeyAndMap(
	key string) (string, Params) {
	var parts []string
	parts = strings.Split(key, ".")
	current := c.root
	for i := 0; i < len(parts)-1; i++ {
		next, found := current[parts[i]]
		if !found {
			return "", nil
		}
		var ok bool
		current, ok = next.(Params)
		if !ok {
			return "", nil
		}
	}
	return parts[len(parts)-1], current
}

// Set 设置键值对
// 统一key的格式为小写字母
// 如果传入的值符合Params的要求，通过root进行设置
// 如果为非Params类型，则直接赋值
func (c *defaultConfigProvider) Set(k string, v any) {
	k = strings.ToLower(k)

	if p, ok := ToParamsAndPrepare(v); ok {
		// Set the values directly in root.
		c.root.Set(p)
	} else {
		c.root[k] = v
	}

	return
}

// SetDefaults will set values from params if not already set.
func (c *defaultConfigProvider) SetDefaults(
	params Params) {
	PrepareParams(params)
	for k, v := range params {
		if _, found := c.root[k]; !found {
			c.root[k] = v
		}
	}
}

// ToParamsAndPrepare converts in to Params and prepares it for use.
// If in is nil, an empty map is returned.
// See PrepareParams.
func ToParamsAndPrepare(in any) (Params, bool) {
	if IsNil(in) {
		return Params{}, true
	}
	m, err := ToStringMapE(in)
	if err != nil {
		return nil, false
	}
	PrepareParams(m)
	return m, true
}

// IsNil reports whether v is nil.
func IsNil(v any) bool {
	if v == nil {
		return true
	}

	value := reflect.ValueOf(v)
	switch value.Kind() {
	case reflect.Chan, reflect.Func,
		reflect.Interface, reflect.Map,
		reflect.Ptr, reflect.Slice:
		return value.IsNil()
	}

	return false
}

// ToStringMapE converts in to map[string]interface{}.
func ToStringMapE(in any) (map[string]any, error) {
	switch vv := in.(type) {
	case Params:
		return vv, nil
	case map[string]string:
		var m = map[string]any{}
		for k, v := range vv {
			m[k] = v
		}
		return m, nil

	default:
		fmt.Println("value type not supported yet")
		return nil, nil
	}
}

// PrepareParams
// * makes all the keys lower cased
// * This will modify the map given.
// * Any nested map[string]interface{}, map[string]string
// * will be converted to Params.
func PrepareParams(m Params) {
	for k, v := range m {
		var retyped bool
		lKey := strings.ToLower(k)

		switch vv := v.(type) {
		case map[string]any:
			var p Params = v.(map[string]any)
			v = p
			PrepareParams(p)
			retyped = true
		case map[string]string:
			p := make(Params)
			for k, v := range vv {
				p[k] = v
			}
			v = p
			PrepareParams(p)
			retyped = true
		}

		if retyped || k != lKey {
			delete(m, k)
			m[lKey] = v
		}
	}
}

func main() {
	// 新建Config Provider实例
	// 实例中defaultConfigProvider实现了接口
	provider := New()

	// 模拟设置用户自定义配置项
	// config.toml中关于主题的配置信息
	// 类型是map[string]string
	// 需要转换成map[string]any，也就是Params类型
	provider.Set("", map[string]string{
		"theme": "mytheme",
	})

	// 模拟默认配置项
	// 超时默认时间为30秒
	provider.SetDefaults(Params{
		"timeout": "30s",
	})

	// 输出提前设置的所有配置信息
	fmt.Printf("%#v\n", provider.Get(""))
	fmt.Printf("%#v\n", provider.Get("theme"))
	fmt.Printf("%#v\n", provider.Get("timeout"))
}

# 输出Config Provider提前设置好的信息
# 包括用户自定义信息，和默认信息
# 准备Input：自定义信息，默认信息
# 得到Output: 通过Config Provider获取所有配置信息
main.Params{"theme":"mytheme", "timeout":"30s"}
"mytheme"
"30s"

Program exited.

func (c *collector) collect() {
	...

	// c.gomods is [], GetMain() returns ni
	projectMod := createProjectModule(c.gomods.GetMain(), c.ccfg.WorkingDir, c.moduleConfig)

	// module structure, [project, others...]
	if err := c.addAndRecurse(projectMod, false); err != nil {
		c.err = err
		return
	}

	...
}

package main

import "fmt"

type Mount struct {
	// relative path in source repo, e.g. "scss"
	Source string
	// relative target path, e.g. "assets/bootstrap/scss"
	Target string
	// any language code associated with this mount.
	Lang string
}

type Import struct {
	// Module path
	Path string
}

// Config holds a module config.
type Config struct {
	Mounts  []Mount
	Imports []Import
}

type Module interface {
	// Config The decoded module config and mounts.
	Config() Config
	// Owner In the dependency tree, this is the first module that defines this module
	// as a dependency.
	Owner() Module
	// Mounts Any directory remappings.
	Mounts() []Mount
}

type Modules []Module

var modules Modules

// moduleAdapter implemented Module interface
type moduleAdapter struct {
	projectMod bool
	owner      Module
	mounts     []Mount
	config     Config
}

func (m *moduleAdapter) Config() Config {
	return m.config
}
func (m *moduleAdapter) Mounts() []Mount {
	return m.mounts
}
func (m *moduleAdapter) Owner() Module {
	return m.owner
}

// happy path to easily understand
func main() {
	// project module config
	moduleConfig := Config{}

	imports := []string{"mytheme"}
	for _, imp := range imports {
		moduleConfig.Imports = append(moduleConfig.Imports, Import{
			Path: imp,
		})
	}

	// Need to run these after the modules are loaded, but before
	// they are finalized.
	collectHook := func(mods Modules) {
		// Apply default project mounts.
		// Default folder structure for hugo project
		ApplyProjectConfigDefaults(mods[0])
	}

	collectModules(moduleConfig, collectHook)

	for _, m := range modules {
		fmt.Printf("%#v\n", m)
	}
}

// Module folder structure
const (
	ComponentFolderArchetypes = "archetypes"
	ComponentFolderStatic     = "static"
	ComponentFolderLayouts    = "layouts"
	ComponentFolderContent    = "content"
	ComponentFolderData       = "data"
	ComponentFolderAssets     = "assets"
	ComponentFolderI18n       = "i18n"
)

// ApplyProjectConfigDefaults applies default/missing module configuration for
// the main project.
func ApplyProjectConfigDefaults(mod Module) {
	projectMod := mod.(*moduleAdapter)

	type dirKeyComponent struct {
		key          string
		component    string
		multilingual bool
	}

	dirKeys := []dirKeyComponent{
		{"contentDir", ComponentFolderContent, true},
		{"dataDir", ComponentFolderData, false},
		{"layoutDir", ComponentFolderLayouts, false},
		{"i18nDir", ComponentFolderI18n, false},
		{"archetypeDir", ComponentFolderArchetypes, false},
		{"assetDir", ComponentFolderAssets, false},
		{"", ComponentFolderStatic, false},
	}

	var mounts []Mount
	for _, d := range dirKeys {
		if d.multilingual {
			// based on language content configuration
			// multiple language has multiple source folders
			if d.component == ComponentFolderContent {
				mounts = append(mounts, Mount{Lang: "en", Source: "mycontent", Target: d.component})
			}
		} else {
			mounts = append(mounts, Mount{Source: d.component, Target: d.component})
		}
	}

	projectMod.mounts = mounts
}

func collectModules(modConfig Config, hookBeforeFinalize func(m Modules)) {
	projectMod := &moduleAdapter{
		projectMod: true,
		config:     modConfig,
	}

	// module structure, [project, others...]
	addAndRecurse(projectMod)

	// Add the project mod on top.
	modules = append(Modules{projectMod}, modules...)

	if hookBeforeFinalize != nil {
		hookBeforeFinalize(modules)
	}
}

// addAndRecurse Project Imports -> Import imports
func addAndRecurse(owner *moduleAdapter) {
	moduleConfig := owner.Config()

	// theme may depend on other theme
	for _, moduleImport := range moduleConfig.Imports {
		tc := add(owner, moduleImport)
		if tc == nil {
			continue
		}
		// tc is mytheme with no config file
		addAndRecurse(tc)
	}
}

func add(owner *moduleAdapter, moduleImport Import) *moduleAdapter {
	fmt.Printf("start to create `%s` module\n", moduleImport.Path)
	ma := &moduleAdapter{
		owner: owner,
		// in the example, mytheme has no other import
		config: Config{},
	}
	modules = append(modules, ma)
	return ma
}

# collect theme as module
start to create `mytheme` module
# project module has no owner with default mounts
&main.moduleAdapter{projectMod:true, owner:main.Module(nil), mounts:[]main.Mount{main.Mount{Source:"mycontent", Target:"content", Lang:"en"}, main.Mount{Source:"data", Target:"data", Lang:""}, main.Mount{Source:"layouts", Target:"layouts", Lang:""}, main.Mount{Source:"i18n", Target:"i18n", Lang:""}, main.Mount{Source:"archetypes", Target:"archetypes", Lang:""}, main.Mount{Source:"assets", Target:"assets", Lang:""}, main.Mount{Source:"static", Target:"static", Lang:""}}, config:main.Config{Mounts:[]main.Mount(nil), Imports:[]main.Import{main.Import{Path:"mytheme"}}}}
# theme module owned by project module with no import in the example
&main.moduleAdapter{projectMod:false, owner:(*main.moduleAdapter)(0xc000102120), mounts:[]main.Mount(nil), config:main.Config{Mounts:[]main.Mount(nil), Imports:[]main.Import(nil)}}

Program exited.