package main

import (
	"context"
	"fmt"
	"os"
	"sync"
	"time"

	"git.novox.be/novox/mesh-sdk/go/buildstep"
	"git.novox.be/novox/mesh-sdk/go/delivery"
	"git.novox.be/novox/mesh-sdk/go/forgekey"
	"git.novox.be/novox/mesh-sdk/go/health"
)

// CheckRound is how often the module reads the installed toolchain again, beside the check before every step and
// the one every health look makes.
const CheckRound = 10 * time.Minute

// Module is the Node build module's one running state: the node it runs on, its recipe, the toolchain guard, the
// toolchain directory and the states it writes (toolchains, steps).
type Module struct {
	Node string
	// Recipe is the recipe in force. Reload, when set, reads it again at every check (the lock file the mesh
	// writes can change under a running module); a failure to read it is a refusal.
	Recipe Recipe
	Reload func() (Recipe, error)
	// Probe reads the installed Node version (ProbeNode).
	Probe func(ctx context.Context) (string, error)
	// Toolchain installs the toolchain directory; nil in a module that only guards.
	Toolchain *Toolchain
	// Work is the work directory, outside the home: a workspace is <Work>/<step id>/tree. Run runs the commands of a
	// step (a fake in a test). Clock is the time the steps are timed by.
	Work  string
	Run   forgekey.Runner
	Clock func() time.Time
	// Toolchains and Steps are the Put of the states of those names.
	Toolchains, Steps buildstep.Put
	// Emit tells the bus an event (stdio.Emit); nil emits nothing. The guard emits toolchain.reported after each write of
	// the toolchains key, so the indexer, which holds no timer, learns that the bucket exists (issue 1444).
	Emit func(eventType string, body any) error
	// Ctx is the process's context, which a step runs under (the tool call's is cut at 30 s, the step's is not).
	Ctx context.Context
	Say func(format string, a ...any)

	mu      sync.Mutex // guards Recipe
	install sync.Mutex // one install at a time
}

func (m *Module) recipe() Recipe {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.Recipe
}

func (m *Module) guard(r Recipe) buildstep.Guard {
	return buildstep.Guard{Language: "typescript", Want: r.Node, Recipe: r.Version(), Probe: m.Probe, Node: m.Node, Put: m.reportingPut()}
}

// Check reads the installed toolchain, writes <node>.typescript of the toolchains state and answers nil, or the
// refusal (buildstep.Guard.Check). It runs at start, before every step, at every health look and every CheckRound.
func (m *Module) Check(ctx context.Context) error {
	if m.Reload != nil {
		r, err := m.Reload()
		if err != nil {
			return &buildstep.Refusal{Text: err.Error(), Want: RecipeNode}
		}
		m.mu.Lock()
		m.Recipe = r
		m.mu.Unlock()
	}
	return m.guard(m.recipe()).Check(ctx)
}

// Prepare is Check and then the toolchain directory of the recipe in force: what every step runs behind.
func (m *Module) Prepare(ctx context.Context) error {
	if err := m.Check(ctx); err != nil {
		return err
	}
	if m.Toolchain == nil {
		return nil
	}
	m.install.Lock()
	defer m.install.Unlock()
	return m.Toolchain.Ensure(ctx, m.recipe().Version())
}

// Start prepares once, as the module starts, and then every CheckRound until ctx ends.
func (m *Module) Start(ctx context.Context) {
	for {
		if err := m.Prepare(ctx); err != nil && m.Say != nil {
			m.Say("the toolchain: %v", err)
		}
		select {
		case <-ctx.Done():
			return
		case <-time.After(CheckRound):
		}
	}
}

// Health is the module's health (the runtime-health tool, ADR 0366): unhealthy while the toolchain installed is not
// the recipe's, saying both versions, so the controller raises the node's condition. It looks again each time it is
// asked.
func (m *Module) Health(ctx context.Context) health.Answer {
	if err := m.Check(ctx); err != nil {
		return health.Unhealthy(err.Error())
	}
	r := m.recipe()
	return health.Healthy(fmt.Sprintf("node %s installed, as the recipe %s builds with", r.Node, r.Version()))
}

// Long is a tool that runs a long step (ADR 0469 §2): it answers at once with the step's id, and the step ends on
// its key in the steps state. The guard runs inside the step, before run, so a node that refuses ends every step
// refused with both versions named.
func (m *Module) Long(tool string, run func(ctx context.Context, args map[string]any) (any, error)) func(map[string]any) (any, error) {
	return func(args map[string]any) (any, error) {
		id, err := buildstep.Start(m.Ctx, m.Steps, m.Node, tool, func(ctx context.Context) (any, error) {
			if err := m.Prepare(ctx); err != nil {
				return nil, err
			}
			return run(ctx, args)
		})
		if err != nil {
			return nil, err
		}
		key, _ := delivery.StepKey(m.Node, id)
		return map[string]any{"step": id, "key": key, "state": delivery.StepRunning}, nil
	}
}

// Short is a tool that answers in its own call; the guard runs before it, and a refusal is the call's error.
func (m *Module) Short(run func(ctx context.Context, args map[string]any) (any, error)) func(map[string]any) (any, error) {
	return func(args map[string]any) (any, error) {
		if err := m.Prepare(m.Ctx); err != nil {
			return nil, err
		}
		return run(m.Ctx, args)
	}
}

// Status is what the module reports of itself: the node, the recipe, the toolchain found and why it refuses, if it
// does.
func (m *Module) Status(ctx context.Context) map[string]any {
	err := m.Check(ctx)
	installed, _ := m.Probe(ctx)
	r := m.recipe()
	out := map[string]any{"node": m.Node, "recipe": r.Version(), "node-version": r.Node, "installed": installed, "refusing": err != nil}
	if m.Toolchain != nil {
		out["toolchain-dir"] = m.Toolchain.Paths.Dir(r.Version())
		out["toolchain-installed"] = m.Toolchain.Present(r.Version())
	}
	if err != nil {
		out["why"] = err.Error()
	}
	return out
}

func (m *Module) now() time.Time {
	if m.Clock != nil {
		return m.Clock()
	}
	return time.Now()
}

// defaultPath is where a step looks for node, npm, git and ssh when this process was given no PATH.
const defaultPath = "/usr/local/bin:/usr/bin:/bin"

// baseEnv is the environment of a step's command beyond what the step adds: PATH, the account's own HOME (its ssh
// files and git configuration) and a fixed locale. A command is given these and its own words, never this process's
// environment, which holds the module's bus credentials (ADR 0466 §4).
func (m *Module) baseEnv() []string {
	return []string{"PATH=" + pathOrDefault(), "HOME=" + m.Toolchain.homeOrEmpty(), "LC_ALL=C"}
}

func pathOrDefault() string {
	if path := os.Getenv("PATH"); path != "" {
		return path
	}
	return defaultPath
}

// ToolchainReported is the event the guard emits after it writes the toolchains key.
const ToolchainReported = "toolchain.reported"

// reportingPut is the toolchains Put that then emits toolchain.reported with the node and the language. A write that
// failed emits nothing; an emit that failed is said and does not refuse the step.
func (m *Module) reportingPut() buildstep.Put {
	return func(key string, value any) (uint64, error) {
		rev, err := m.Toolchains(key, value)
		if err != nil || m.Emit == nil {
			return rev, err
		}
		if eerr := m.Emit(ToolchainReported, map[string]string{"node": m.Node, "language": "typescript"}); eerr != nil && m.Say != nil {
			m.Say("the event %s could not be emitted: %v", ToolchainReported, eerr)
		}
		return rev, nil
	}
}