package stacks

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

// AppliedComposeFile is the stored copy of the docker-compose.yml an app was last brought up FROM.
//
// WHY IT LIVES IN THE STACK DIRECTORY, and why this exact name: `Syncer.copyTemplates` copies
// EXACTLY `docker-compose.yml` and `.felhom.yml` and nothing else, so any other name in that
// directory is safe from the catalog. Keeping it beside the app means it travels through every path
// that already moves a stack dir, and anyone debugging the box can see it without a tool.
//
// It is the FROZEN definition: when the catalog has moved past an app's pin, this whole file is
// written to docker-compose.yml. Never a substitution of pinned refs into a newer template — a
// template's env and volumes can belong to its version (`wger 2.6` needs a full DB config the older
// template cannot supply), and an old image under a new template is a third broken state nobody
// chose.
const AppliedComposeFile = "applied-compose.yml"

// AppliedComposePath is the single definition of where the stored definition lives.
func AppliedComposePath(stackDir string) string {
	return filepath.Join(stackDir, AppliedComposeFile)
}

// StoreAppliedDefinition writes the compose definition this app is pinned to, atomically.
//
// Atomic tmp+rename for the same reason SaveAppConfig is: the syncer may read this file at any
// moment, and a half-written compose file rendered over a live app is a broken app.
func StoreAppliedDefinition(stackDir string, data []byte) error {
	if len(data) == 0 {
		// NEVER store an empty definition. An empty applied file would later be rendered over the
		// live compose file and take the app down — see the render table's "unreadable or empty"
		// row, which treats it as absent precisely so this cannot happen.
		return fmt.Errorf("refusing to store an empty applied definition for %s", filepath.Base(stackDir))
	}
	path := AppliedComposePath(stackDir)
	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, data, 0o644); err != nil {
		return fmt.Errorf("writing %s: %w", tmp, err)
	}
	if err := os.Rename(tmp, path); err != nil {
		_ = os.Remove(tmp)
		return fmt.Errorf("renaming %s to %s: %w", tmp, path, err)
	}
	return nil
}

// LoadAppliedDefinition returns the stored definition, or an error when there is none or it is
// unusable. An empty file is an ERROR, not empty content — see the render table.
func LoadAppliedDefinition(stackDir string) ([]byte, error) {
	data, err := os.ReadFile(AppliedComposePath(stackDir))
	if err != nil {
		return nil, err
	}
	if len(strings.TrimSpace(string(data))) == 0 {
		return nil, fmt.Errorf("stored applied definition for %s is empty", filepath.Base(stackDir))
	}
	return data, nil
}

// SetPin records what an app is SUPPOSED to run and stores the definition that pin came from.
//
// PIN FIRST, THEN STORE, and the degradation is deliberate: if the pin lands and the store fails,
// the app is pinned with no stored definition, and the render table's own row for that case copies
// the catalog verbatim and WARNs. That is today's behaviour plus a loud line — the same outcome as
// being unpinned, never a silent freeze onto a definition we do not have.
//
// `composeSrc` MUST be the exact bytes the pin was derived from. Passing a different file is how a
// stack ends up frozen onto something it never ran.
func (m *Manager) SetPin(name, stackDir string, pin map[string]string, composeSrc []byte) error {
	if len(pin) == 0 {
		return fmt.Errorf("refusing to pin %s to an empty image set", name)
	}
	cfg := LoadAppConfig(stackDir)
	if cfg == nil {
		// No app.yaml means nothing is deployed here. Not an error — the same no-op
		// SetDesiredState makes for the same reason.
		m.logger.Printf("[DEBUG] [stacks] pin %s: no app.yaml — nothing deployed here, nothing to pin", name)
		return nil
	}

	if !samePin(cfg.PinnedImages, pin) {
		cfg.PinnedImages = pin
		meta := LoadMetadata(stackDir)
		if err := SaveAppConfig(stackDir, cfg, m.encKey, SensitiveEnvVars(&meta)); err != nil {
			return fmt.Errorf("recording pin for %s: %w", name, err)
		}
		m.logger.Printf("[INFO] [stacks] pin %s: %s", name, summarisePin(pin))

		m.mu.Lock()
		if st, ok := m.stacks[name]; ok && st.AppConfig != nil {
			st.AppConfig.PinnedImages = pin
		}
		m.mu.Unlock()
	}

	if err := StoreAppliedDefinition(stackDir, composeSrc); err != nil {
		// Loud, and NOT fatal to the pin — see the comment above.
		m.logger.Printf("[ERROR] [stacks] pin %s: the pin is recorded but its definition could not be stored (the app is unaffected; the catalog will be copied verbatim until this is fixed): %v", name, err)
	}
	return nil
}

// samePin compares two pins by content so an unchanged pin does not rewrite app.yaml — that file
// holds encrypted secrets and rewriting it for no new information is pure risk (the SetDesiredState
// rule).
func samePin(a, b map[string]string) bool {
	if len(a) != len(b) {
		return false
	}
	for k, va := range a {
		if vb, ok := b[k]; !ok || va != vb {
			return false
		}
	}
	return true
}

// summarisePin renders a pin for ONE log line. Image refs only — this file never logs anything out
// of app.yaml's env map, which holds encrypted secrets.
func summarisePin(pin map[string]string) string {
	svcs := make([]string, 0, len(pin))
	for svc := range pin {
		svcs = append(svcs, svc)
	}
	sort.Strings(svcs)
	parts := make([]string, 0, len(svcs))
	for _, svc := range svcs {
		parts = append(parts, svc+"="+pin[svc])
	}
	return strings.Join(parts, ", ")
}

// ComposePathIn resolves a stack directory's compose file, honouring the .yml/.yaml pair exactly as
// ScanStacks does. One rule, so a caller cannot pin from a file the scanner would not have read.
func ComposePathIn(stackDir string) string {
	p := filepath.Join(stackDir, "docker-compose.yml")
	if _, err := os.Stat(p); err == nil {
		return p
	}
	alt := filepath.Join(stackDir, "docker-compose.yaml")
	if _, err := os.Stat(alt); err == nil {
		return alt
	}
	return p // the canonical name; the caller's read will report the real error
}

// PinFromCompose reads a compose file and returns both the pin it implies and its exact bytes, so a
// caller cannot accidentally pin from one file and store another.
func PinFromCompose(composePath string) (map[string]string, []byte, error) {
	images, err := ParseComposeImages(composePath)
	if err != nil {
		return nil, nil, err
	}
	if len(images) == 0 {
		return nil, nil, fmt.Errorf("%s declares no images", composePath)
	}
	data, err := os.ReadFile(composePath)
	if err != nil {
		return nil, nil, err
	}
	return images, data, nil
}

// --- what the syncer is told ---

// RenderPlan is the per-app answer the stack manager gives the catalog syncer.
//
// It carries FACTS, not a decision: the render table lives in the syncer, which is the thing doing
// the writing. The syncer must never read app.yaml itself — that file is the manager's and carries
// encrypted values — so everything it needs to apply the table comes through here.
type RenderPlan struct {
	Deployed    bool
	Deploying   bool
	Protected   bool
	Pinned      map[string]string // service -> image ref; nil/empty means UNPINNED
	AppliedPath string            // the stored definition; "" when none is stored
	// StackDir lets the syncer REFRESH the stored definition when it copies the catalog verbatim
	// into a pinned app whose images still match. See Syncer.renderSource — without that refresh the
	// stored definition goes stale relative to the fixes that flowed after it, and the freeze would
	// later undo them. Found by the live validation of v0.235.0, not by review.
	StackDir string
}

// RenderPlanFor answers for one app by name. Unknown apps come back as an empty plan, which the
// syncer reads as "not deployed" — i.e. copy verbatim, exactly the pre-v0.235.0 behaviour.
func (m *Manager) RenderPlanFor(name string) RenderPlan {
	s, ok := m.GetStack(name)
	if !ok {
		return RenderPlan{}
	}
	plan := RenderPlan{
		Deployed:  s.Deployed,
		Deploying: s.Deploying,
		Protected: s.Protected,
	}
	if s.AppConfig != nil && len(s.AppConfig.PinnedImages) > 0 {
		plan.Pinned = s.AppConfig.PinnedImages
	}
	stackDir := filepath.Dir(s.ComposePath)
	plan.StackDir = stackDir
	if _, err := LoadAppliedDefinition(stackDir); err == nil {
		plan.AppliedPath = AppliedComposePath(stackDir)
	}
	return plan
}

// --- adoption ---

// AdoptPins gives a pin to every deployed app that has none, and stores the definition it is
// running. Call ONCE at startup, immediately AFTER BackfillInstalledImages so an app the backfill
// has just observed can be pinned in the same boot.
//
// ── IT NEVER GUESSES, AND THAT IS MOST OF THE CODE ───────────────────────────────────────────
//
// Two skips, each with a reason that is not interchangeable:
//
//  1. The observation is INCOMPLETE (stopped, crash-looping, mid-anything). We do not know what the
//     app runs, so we cannot say what it should run. Reuses observationCoversTemplate — the SAME
//     completeness rule the backfill uses, deliberately not a second one.
//  2. The observation is complete but DIFFERS from the current template. The app is already running
//     something the catalog no longer offers, and we have no stored definition for it. Pinning here
//     would be right, but the FREEZE would then render a definition we do not possess — and the only
//     way to manufacture one is to substitute the running refs into the newer template, which is
//     exactly the third-broken-state this design refuses (see AppliedComposeFile).
//
// In both cases the app keeps behaving exactly as it did before v0.235.0, loudly. Absent means
// unknown; unknown is never resolved by inventing an answer.
//
// It reads and writes FILES only. It starts, stops and touches no container.
func (m *Manager) AdoptPins() int {
	pinned, alreadyPinned, skippedIncomplete, skippedMismatch := 0, 0, 0, 0

	for _, s := range m.GetStacks() {
		if !s.Deployed || s.Protected || s.Deploying {
			continue
		}
		if s.AppConfig != nil && len(s.AppConfig.PinnedImages) > 0 {
			alreadyPinned++
			continue
		}
		stackDir := filepath.Dir(s.ComposePath)

		tpl, err := ParseComposeImages(s.ComposePath)
		if err != nil || len(tpl) == 0 {
			m.logger.Printf("[WARN] [stacks] pin adoption: %s left UNPINNED — its compose file declares no readable images (%v). It keeps pre-v0.235.0 behaviour.", s.Name, err)
			skippedIncomplete++
			continue
		}

		var observed map[string]InstalledImage
		if s.AppConfig != nil {
			observed = s.AppConfig.InstalledImages
		}
		if !observationCoversTemplate(observed, tpl) {
			m.logger.Printf("[WARN] [stacks] pin adoption: %s left UNPINNED — no complete record of what it is running (%d of %d service(s) observed). It keeps pre-v0.235.0 behaviour.",
				s.Name, len(observed), len(tpl))
			skippedIncomplete++
			continue
		}

		if diff := pinMismatch(observed, tpl); diff != "" {
			m.logger.Printf("[WARN] [stacks] pin adoption: %s left UNPINNED — it is running something the current template no longer offers, and there is no stored definition for it: %s. It keeps pre-v0.235.0 behaviour.",
				s.Name, diff)
			skippedMismatch++
			continue
		}

		_, data, err := PinFromCompose(s.ComposePath)
		if err != nil {
			m.logger.Printf("[WARN] [stacks] pin adoption: %s: %v", s.Name, err)
			skippedIncomplete++
			continue
		}
		if err := m.SetPin(s.Name, stackDir, tpl, data); err != nil {
			m.logger.Printf("[ERROR] [stacks] pin adoption: %s: %v", s.Name, err)
			continue
		}
		m.storeAppliedMetaFrom(s.Name, stackDir, filepath.Join(stackDir, ".felhom.yml")) // adopted only when running == template
		pinned++
	}

	// A POSITIVE OBSERVABLE EITHER WAY (standing rule 3): "0 pinned" and "the pass never ran" must
	// not look the same in a log.
	m.logger.Printf("[INFO] [stacks] pin adoption: %d pinned, %d already pinned, %d left unpinned (%d not completely observed, %d running something the template no longer offers)",
		pinned, alreadyPinned, skippedIncomplete+skippedMismatch, skippedIncomplete, skippedMismatch)
	return pinned
}

// pinMismatch returns a human description of the first service whose RUNNING reference differs from
// what the template pins, or "" when they agree everywhere. Deterministic order so two runs produce
// the same line.
func pinMismatch(observed map[string]InstalledImage, tpl map[string]string) string {
	svcs := make([]string, 0, len(tpl))
	for svc := range tpl {
		svcs = append(svcs, svc)
	}
	sort.Strings(svcs)
	var diffs []string
	for _, svc := range svcs {
		got, ok := observed[svc]
		if !ok {
			continue // completeness was already checked
		}
		if got.Ref != tpl[svc] {
			diffs = append(diffs, fmt.Sprintf("%s runs %s, template offers %s", svc, got.Ref, tpl[svc]))
		}
	}
	return strings.Join(diffs, "; ")
}

// CatalogTemplatePath is where the syncer's git clone keeps one app's template. It is the ONLY
// definition of that layout outside the syncer, and the badge and the update path both use it.
func (m *Manager) CatalogTemplatePath(appName, filename string) string {
	return filepath.Join(m.cfg.Paths.DataDir, "catalog-cache", "templates", appName, filename)
}

// advancePinToCatalog moves a PINNED app onto the catalog's current definition: it writes the
// catalog template over the live compose file, records the new pin, and stores that definition as
// the applied one. Called by UpdateStack BEFORE the pull — see the comment at that call site.
//
// AN UNPINNED APP IS LEFT ALONE AND THIS RETURNS NIL. It behaves exactly as it did before v0.235.0:
// the syncer has already copied the catalog verbatim into its stack dir, so `pull` + `up -d` do
// today's job with no help from here.
func (m *Manager) advancePinToCatalog(name, stackDir string) error {
	cfg := LoadAppConfig(stackDir)
	if cfg == nil || len(cfg.PinnedImages) == 0 {
		return nil // unpinned — today's behaviour, unchanged
	}

	src := m.CatalogTemplatePath(name, "docker-compose.yml")
	pin, data, err := PinFromCompose(src)
	if err != nil {
		// REFUSE rather than silently update to the frozen definition (which would be a no-op
		// reported as success). Names the cause so the operator is not left guessing.
		return fmt.Errorf("cannot read the catalog's current definition for %s (%s): %w", name, src, err)
	}

	live := ComposePathIn(stackDir)
	if err := StoreAppliedDefinition(stackDir, data); err != nil {
		return fmt.Errorf("storing the new applied definition for %s: %w", name, err)
	}
	if err := os.WriteFile(live, data, 0o644); err != nil {
		return fmt.Errorf("rendering the catalog definition for %s: %w", name, err)
	}

	cfg.PinnedImages = pin
	meta := LoadMetadata(stackDir)
	if err := SaveAppConfig(stackDir, cfg, m.encKey, SensitiveEnvVars(&meta)); err != nil {
		return fmt.Errorf("recording the advanced pin for %s: %w", name, err)
	}
	m.mu.Lock()
	if st, ok := m.stacks[name]; ok && st.AppConfig != nil {
		st.AppConfig.PinnedImages = pin
	}
	m.mu.Unlock()

	// v0.263.2: the new version's own .felhom.yml becomes the pinned version's record.
	m.storeAppliedMetaFrom(name, stackDir, m.CatalogTemplatePath(name, ".felhom.yml"))
	m.logger.Printf("[INFO] [stacks] update %s: pin advanced to the catalog's current definition (%s)", name, summarisePin(pin))
	return nil
}