package catalogue

import (
	"encoding/json"
	"fmt"
	"regexp"
	"slices"
)

// A module declares its config (novox/hq ADR 0348 §1, §4, §5, §6, §8, §11; design 57 package K1, issue 660).
//
// **One concept, two spellings for a while.** "Config" replaces "settings": the manifest says `config` for
// `settings`, `takes-config` for `takes-settings` and `${config:<key>}` for `${setting:<key>}`. The old names stay
// accepted as aliases until every module has moved (ADR 0348 §1), and a module uses one form or the other, never
// both. The config form is read into the very fields the settings form fills — Settings, a mergeable file's
// takes-settings and `${setting:<key>}` — so composition has one path and `${config:<key>}` fills exactly as
// `${setting:<key>}` does: a module rewritten from settings to config composes byte-identically. It is written
// back in the form it was read in, so what the mesh holds is what its author wrote.
//
// **A moved module is held to the whole declaration.** Under `config` every value has a type (number, string or
// boolean; an object or a list only when trusted), a description including its unit, its validation (enum,
// minimum and maximum, pattern), whether it is trusted, optionally the predefined key it falls back to, and either
// a default or `required`; it lands in a file or is read at runtime (`runtime: true`); every mergeable file names
// the keys it takes; a `reload-on` or `restart-on` names a file the module declares. A module not yet moved keeps
// today's form and today's rules (SettingProblems, TakenSettingsProblems) until the catalogue's list of such
// modules is empty (ADR 0348 §11).
//
// **A required value nothing sets** is the operator's own: it composes as an operator's setting nobody gave does
// today, refused by name at composition (UnsetSettingError). Who reports it once mesh-config answers values is the
// provisioner's (ADR 0349), not this file's.

// ConfigField is the manifest key a module declares its config values under.
const ConfigField = "config"

// TakesConfigField is the key a mergeable file names the config values it takes by.
const TakesConfigField = "takes-config"

// SettingsField is the old name of ConfigField, read as its alias.
const SettingsField = "settings"

// configRef is how a file asks for a config value: ${config:<key>}, the same keys as settingRef.
var configRef = regexp.MustCompile(`\$\{config:([a-z0-9][a-z0-9_.-]*)\}`)

// takesConfigKey and takesSettingsKey are the two spellings as a key of a JSON object. A string value is never
// followed by a colon, and a quote inside a string is escaped, so these match only keys.
var (
	takesConfigKey   = regexp.MustCompile(`"` + TakesConfigField + `"(\s*):`)
	takesSettingsKey = regexp.MustCompile(`"` + TakesSettingsField + `"(\s*):`)
)

// The types a config value may have (ADR 0348 §4).
const (
	ConfigNumber  = "number"
	ConfigString  = "string"
	ConfigBoolean = "boolean"
	ConfigObject  = "object"
	ConfigList    = "list"
)

// accountFacts are what the mesh places for a module's account, never config values (ADR 0348 §11).
var accountFacts = map[string]bool{"puid": true, "pgid": true}

// configForms is which of the two forms a manifest was written in, by the words of each it uses.
type configForms struct {
	config, settings []string
}

// DeclaresConfig is whether the manifest is written in the config form: `config`, `takes-config` or
// `${config:<key>}` (ADR 0348 §1, §11).
func (m Manifest) DeclaresConfig() bool { return len(m.forms.config) > 0 }

// toSettingsForm is raw with the config form's placeholders and takes-config read as the settings form's, and
// which words of each form it used. `config` itself is a top-level key, renamed where the keys are read
// (UnmarshalJSON).
func toSettingsForm(raw []byte) ([]byte, configForms) {
	var f configForms
	if configRef.Match(raw) {
		f.config = append(f.config, "${config:…}")
	}
	if takesConfigKey.Match(raw) {
		f.config = append(f.config, TakesConfigField)
	}
	if settingRef.Match(raw) {
		f.settings = append(f.settings, "${setting:…}")
	}
	if takesSettingsKey.Match(raw) {
		f.settings = append(f.settings, TakesSettingsField)
	}
	if len(f.config) == 0 {
		return raw, f
	}
	raw = configRef.ReplaceAllFunc(raw, func(ref []byte) []byte {
		return []byte("${setting:" + string(configRef.FindSubmatch(ref)[1]) + "}")
	})
	raw = takesConfigKey.ReplaceAllFunc(raw, func(key []byte) []byte {
		return []byte(`"` + TakesSettingsField + `"` + string(takesConfigKey.FindSubmatch(key)[1]) + ":")
	})
	return raw, f
}

// toConfigForm is a manifest written in the settings form's words, as JSON, in the config form's: what
// toSettingsForm and UnmarshalJSON read, written back.
func toConfigForm(raw []byte) ([]byte, error) {
	var keys map[string]json.RawMessage
	if err := json.Unmarshal(raw, &keys); err != nil {
		return nil, err
	}
	if settings, has := keys[SettingsField]; has {
		keys[ConfigField] = settings
		delete(keys, SettingsField)
		var err error
		if raw, err = json.Marshal(keys); err != nil {
			return nil, err
		}
	}
	raw = settingRef.ReplaceAllFunc(raw, func(ref []byte) []byte {
		return []byte("${config:" + string(settingRef.FindSubmatch(ref)[1]) + "}")
	})
	raw = takesSettingsKey.ReplaceAllFunc(raw, func(key []byte) []byte {
		return []byte(`"` + TakesConfigField + `"` + string(takesSettingsKey.FindSubmatch(key)[1]) + ":")
	})
	return raw, nil
}

// configDeclaration is the config form's declaration as written: nothing of the settings form's, and nothing
// unsaid.
type configDeclaration struct {
	Type        string   `json:"type,omitempty"`
	Description string   `json:"description,omitempty"`
	Enum        []any    `json:"enum,omitempty"`
	Minimum     *float64 `json:"minimum,omitempty"`
	Maximum     *float64 `json:"maximum,omitempty"`
	Pattern     string   `json:"pattern,omitempty"`
	Trusted     bool     `json:"trusted,omitempty"`
	Predefined  string   `json:"predefined,omitempty"`
	Default     any      `json:"default,omitempty"`
	Required    bool     `json:"required,omitempty"`
	Runtime     bool     `json:"runtime,omitempty"`
}

// MarshalJSON writes a settings declaration exactly as before, and a config declaration without the settings
// form's kind and why, and without a default it does not have.
func (d SettingDeclaration) MarshalJSON() ([]byte, error) {
	type plain SettingDeclaration
	if d.Kind != "" || d.Why != "" {
		return json.Marshal(plain(d))
	}
	return json.Marshal(configDeclaration{Type: d.Type, Description: d.Description, Enum: d.Enum,
		Minimum: d.Minimum, Maximum: d.Maximum, Pattern: d.Pattern, Trusted: d.Trusted, Predefined: d.Predefined,
		Default: d.Default, Required: d.Required, Runtime: d.Runtime})
}

// renamedTaken is every value a mergeable file takes under a name of its own, with that name (issue 751).
func renamedTaken(m Manifest) map[string]string {
	out := map[string]string{}
	for _, r := range m.Resources {
		if how, _ := r["merge"].(string); how == "" {
			continue
		}
		for _, e := range takenEntries(r[TakesSettingsField]) {
			if e.renamed {
				out[e.key] = e.as
			}
		}
	}
	return out
}

// validationProblems is what is wrong with a declaration's validation, and its default against it.
func validationProblems(d SettingDeclaration) []string {
	var problems []string
	isNumber := d.Type == ConfigNumber
	if len(d.Enum) > 0 && d.Type != ConfigNumber && d.Type != ConfigString {
		problems = append(problems, fmt.Sprintf("an enum is for a number or a string, and this is a %s", d.Type))
	}
	if (d.Minimum != nil || d.Maximum != nil) && !isNumber {
		problems = append(problems, fmt.Sprintf("a minimum or maximum is for a number, and this is a %s", d.Type))
	}
	if d.Minimum != nil && d.Maximum != nil && *d.Minimum > *d.Maximum {
		problems = append(problems, fmt.Sprintf("its minimum %v is above its maximum %v", *d.Minimum, *d.Maximum))
	}
	var pattern *regexp.Regexp
	if d.Pattern != "" {
		if d.Type != ConfigString {
			problems = append(problems, fmt.Sprintf("a pattern is for a string, and this is a %s", d.Type))
		}
		var err error
		if pattern, err = regexp.Compile(`^(?:` + d.Pattern + `)$`); err != nil {
			problems = append(problems, fmt.Sprintf("its pattern %q is not a regular expression: %v", d.Pattern, err))
		}
	}
	for _, v := range d.Enum {
		if !ofType(v, d.Type) {
			problems = append(problems, fmt.Sprintf("its enum holds %v, which is not a %s", v, d.Type))
		}
	}
	if d.Default == nil {
		return problems
	}
	if !ofType(d.Default, d.Type) {
		if d.Type != "" {
			problems = append(problems, fmt.Sprintf("its default %v is not a %s", d.Default, d.Type))
		}
		return problems
	}
	if len(d.Enum) > 0 && !slices.ContainsFunc(d.Enum, func(v any) bool { return v == d.Default }) {
		problems = append(problems, fmt.Sprintf("its default %v is not one of %v", d.Default, d.Enum))
	}
	if n, ok := d.Default.(float64); ok {
		if d.Minimum != nil && n < *d.Minimum {
			problems = append(problems, fmt.Sprintf("its default %v is below its minimum %v", n, *d.Minimum))
		}
		if d.Maximum != nil && n > *d.Maximum {
			problems = append(problems, fmt.Sprintf("its default %v is above its maximum %v", n, *d.Maximum))
		}
	}
	if s, ok := d.Default.(string); ok && pattern != nil && !pattern.MatchString(s) {
		problems = append(problems, fmt.Sprintf("its default %q does not match its pattern %q", s, d.Pattern))
	}
	return problems
}

// ofType is whether a value read from JSON is of a config type.
func ofType(v any, kind string) bool {
	switch v.(type) {
	case float64:
		return kind == ConfigNumber
	case string:
		return kind == ConfigString
	case bool:
		return kind == ConfigBoolean
	case map[string]any:
		return kind == ConfigObject
	case []any:
		return kind == ConfigList
	}
	return false
}