package client

import (
	"fmt"
	"io"
	"os"
	"time"

	"github.com/m3tam3re/agent-lib/internal/deploy"
	"github.com/m3tam3re/agent-lib/internal/gitsource"
	"github.com/m3tam3re/agent-lib/internal/lockfile"
	"github.com/m3tam3re/agent-lib/internal/target"
)

// SyncReport summarizes one planner-driven sync run.
type SyncReport struct {
	Revision string
	Deployed int
	Updated  int
	Kept     int
	Removed  int
	Skipped  int
	Left     int
	Manifest string
}

// ExecutePlan applies a plan item by item: deploys and removes are atomic
// per item, every skip+warn and leave+warn is appended to the warning log
// with item name and reason, and the manifest is rewritten once at the end.
func ExecutePlan(tree *gitsource.GitTree, plan []PlanEntry, manifest *Manifest, paths StatePaths, rev string, stdout io.Writer) (*SyncReport, error) {
	report := &SyncReport{Revision: rev, Manifest: paths.Manifest}
	var warnings []string

	for _, e := range plan {
		key := manifestKey(e.Type, e.Name)
		switch e.Action {
		case ActDeploy, ActUpdate:
			if err := deployEntry(tree, e); err != nil {
				return nil, fmt.Errorf("%s %s/%s: %w", e.Action, e.Type, e.Name, err)
			}
			manifest.Items[key] = &ManifestItem{
				Name: e.Name, Type: e.Type, Origin: e.Origin, Revision: rev, Hash: e.NewHash,
			}
			if e.Action == ActDeploy {
				report.Deployed++
			} else {
				report.Updated++
			}
		case ActKeep:
			report.Kept++
		case ActRemove:
			if err := os.RemoveAll(e.DstPath); err != nil {
				return nil, fmt.Errorf("removing %s/%s: %w", e.Type, e.Name, err)
			}
			delete(manifest.Items, key)
			report.Removed++
		case ActSkip:
			warnings = append(warnings, fmt.Sprintf("SKIP %s/%s: %s", e.Type, e.Name, e.Reason))
			report.Skipped++
		case ActLeave:
			warnings = append(warnings, fmt.Sprintf("LEAVE %s/%s: %s", e.Type, e.Name, e.Reason))
			report.Left++
		}
	}

	manifest.Version = ManifestVersion
	manifest.Revision = rev
	if err := manifest.Save(paths.Manifest); err != nil {
		return nil, err
	}
	if len(warnings) > 0 {
		if err := appendWarnings(paths.LogFile, warnings); err != nil {
			fmt.Fprintf(stdout, "warning: could not write sync log: %v\n", err)
		}
	}

	printPlannedSyncReport(stdout, report)
	return report, nil
}

func deployEntry(tree *gitsource.GitTree, e PlanEntry) error {
	if e.Type == lockfile.TypeSkill {
		return deploy.Dir(tree, e.RelPath, e.DstPath)
	}
	return deploy.File(tree, e.RelPath, e.DstPath)
}

// appendWarnings adds timestamped warning lines to the sync log.
func appendWarnings(logPath string, warnings []string) error {
	f, err := os.OpenFile(logPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
	if err != nil {
		return err
	}
	defer f.Close()
	stamp := time.Now().UTC().Format(time.RFC3339)
	for _, w := range warnings {
		if _, err := fmt.Fprintf(f, "%s %s\n", stamp, w); err != nil {
			return err
		}
	}
	return nil
}

// diskFacts observes every deployed path the planner can care about:
// manifest items, current inventory items, and unmanaged occupants of the
// target directories.
func diskFacts(oc *target.OpenCode, manifest *Manifest, items []PlannedItem) map[string]DiskFact {
	facts := map[string]DiskFact{}
	observe := func(typ, name string) {
		key := manifestKey(typ, name)
		if _, seen := facts[key]; seen {
			return
		}
		path, ok := oc.DeployPath(typ, name)
		if !ok {
			return
		}
		if _, err := os.Stat(path); err != nil {
			facts[key] = DiskFact{}
			return
		}
		hash, err := HashDiskPath(typ, path)
		if err != nil {
			hash = ""
		}
		facts[key] = DiskFact{Exists: true, Hash: hash}
	}

	for _, rec := range manifest.Items {
		observe(rec.Type, rec.Name)
	}
	for _, it := range items {
		observe(it.Type, it.Name)
	}
	for key := range oc.ScanTargetDirs() {
		if _, seen := facts[key]; !seen {
			facts[key] = DiskFact{Exists: true}
		}
	}
	return facts
}

func printPlannedSyncReport(w io.Writer, r *SyncReport) {
	fmt.Fprintf(w, "synced to revision %s\n", shortRev(r.Revision))
	fmt.Fprintf(w, "  deployed: %d\n", r.Deployed)
	fmt.Fprintf(w, "  updated:  %d\n", r.Updated)
	fmt.Fprintf(w, "  kept:     %d\n", r.Kept)
	fmt.Fprintf(w, "  removed:  %d\n", r.Removed)
	if r.Skipped > 0 {
		fmt.Fprintf(w, "  skipped (local modifications kept): %d\n", r.Skipped)
	}
	if r.Left > 0 {
		fmt.Fprintf(w, "  unmanaged items left untouched: %d\n", r.Left)
	}
	fmt.Fprintf(w, "  manifest: %s\n", r.Manifest)
}

func shortRev(rev string) string {
	if len(rev) > 12 {
		return rev[:12]
	}
	return rev
}