package delivery

import (
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"time"
)

// ToolchainsState is the name of the state a build module keeps its toolchains in; its bucket is
// `<module>_toolchains`, built as the SDK names a module's state, by ToolchainsBucket (novox/hq ADR 0465 clause 2).
const ToolchainsState = "toolchains"

// ToolchainsBucket is the bucket of a build module's toolchains.
func ToolchainsBucket(module string) string { return module + "_" + ToolchainsState }

// ToolchainNoReport is the reason AgreedToolchain gives when no node has reported a language's toolchain.
const ToolchainNoReport = "toolchain not yet reported"

func checkToolchainLanguage(language string) error {
	switch language {
	case "go", "typescript":
		return nil
	}
	return fmt.Errorf("delivery: the toolchain language %q is not go or typescript", language)
}

// ToolchainKey is the key of a node's toolchain of one language: `<node>.<language>`. It refuses a node that is not a
// name and a language other than go or typescript.
func ToolchainKey(node, language string) (string, error) {
	if err := checkName("node", node); err != nil {
		return "", err
	}
	if err := checkToolchainLanguage(language); err != nil {
		return "", err
	}
	return node + "." + language, nil
}

// ParseToolchainKey is the inverse of ToolchainKey.
func ParseToolchainKey(key string) (node, language string, err error) {
	node, language, ok := strings.Cut(key, ".")
	if !ok {
		return "", "", fmt.Errorf("delivery: %q is not a toolchain key, <node>.<language>", key)
	}
	if _, err := ToolchainKey(node, language); err != nil {
		return "", "", fmt.Errorf("delivery: %q is not a toolchain key: %w", key, err)
	}
	return node, language, nil
}

// Toolchain is the value of a toolchains key: the version of the language's toolchain installed on the node and the
// build module's recipe version, and when the module saw them.
type Toolchain struct {
	V        int       `json:"v"`
	Language string    `json:"language"`
	Version  string    `json:"version"`
	Recipe   string    `json:"recipe"`
	At       time.Time `json:"at"`
}

func (t Toolchain) check() error {
	if err := checkToolchainLanguage(t.Language); err != nil {
		return err
	}
	if t.Version == "" || t.Recipe == "" {
		return fmt.Errorf("delivery: a %s toolchain needs its version and its recipe", t.Language)
	}
	return nil
}

// EncodeToolchain is t as JSON at Version; it refuses a language other than go or typescript and an empty version or
// recipe.
func EncodeToolchain(t Toolchain) ([]byte, error) {
	if err := t.check(); err != nil {
		return nil, err
	}
	t.V = Version
	return json.Marshal(t)
}

// DecodeToolchain reads a toolchains value; it refuses an unknown version (ErrUnknownVersion) and what EncodeToolchain
// refuses.
func DecodeToolchain(data []byte) (Toolchain, error) {
	var t Toolchain
	if err := decode(data, &t); err != nil {
		return Toolchain{}, err
	}
	if err := t.check(); err != nil {
		return Toolchain{}, err
	}
	return t, nil
}

// NodeToolchain is one node's entry of a language, as read from the toolchains bucket.
type NodeToolchain struct {
	Node string
	Toolchain
}

// AgreedToolchain is the one Toolchain2 every node's entry of a language agrees on, or none and why: "toolchain not
// yet reported" with no entries, and "builders disagree" naming each differing version and recipe with the nodes
// reporting it when two differ (novox/hq ADR 0405 clause 2). The answer does not depend on the entries' order. The
// entries must all be of one language.
func AgreedToolchain(entries []NodeToolchain) (tc Toolchain2, none string) {
	if len(entries) == 0 {
		return Toolchain2{}, ToolchainNoReport
	}
	groups := map[Toolchain2][]string{}
	for _, e := range entries {
		k := Toolchain2{Language: e.Language, Version: e.Version, Recipe: e.Recipe}
		groups[k] = append(groups[k], e.Node)
	}
	if len(groups) == 1 {
		for k := range groups {
			return k, ""
		}
	}
	parts := make([]string, 0, len(groups))
	for k, nodes := range groups {
		sort.Strings(nodes)
		parts = append(parts, fmt.Sprintf("%s recipe %s on %s", k.Version, k.Recipe, strings.Join(nodes, ", ")))
	}
	sort.Strings(parts)
	return Toolchain2{}, "builders disagree: " + strings.Join(parts, "; ")
}