package gsp

import (
	"encoding/json"
	"fmt"
	"path/filepath"
	"sort"
	"strings"
)

func (p *Project) Validate(stage string) Report {
	report := Report{OK: true}
	for _, issue := range p.LoadIssues {
		switch issue.Level {
		case "error":
			report.Errors = append(report.Errors, issue)
			report.OK = false
		case "warning":
			report.Warnings = append(report.Warnings, issue)
		default:
			report.Notices = append(report.Notices, issue)
		}
	}
	if p.Manifest != nil {
		if p.Manifest.GSPVersion == "" {
			report.addWarning("missing_gsp_version", "", p.Manifest.File, "manifest has no gspVersion")
		} else if !SupportsGSPVersion(p.Manifest.GSPVersion) {
			report.addError("unsupported_gsp_version", "", p.Manifest.File, fmt.Sprintf("GSP version %q is not supported by this toolkit", p.Manifest.GSPVersion))
		}
	}
	p.validateFieldRegistry(&report)
	for _, unit := range p.Units {
		if unit.ID == "" {
			report.addError("missing_id", "", unit.File, "GSP requires id")
		}
		if unit.Resolution != "" {
			if _, ok := resolutionValue(unit.Resolution); !ok {
				report.addError("invalid_resolution", unit.ID, unit.File, fmt.Sprintf("resolution %q is not allowed", unit.Resolution))
			}
		}
		for _, rel := range unit.With {
			if _, ok := p.ByID[rel.ID]; !ok {
				report.addError("missing_with", unit.ID, unit.File, fmt.Sprintf("with references missing GSP %q", rel.ID))
			}
		}
		for _, link := range unit.Links {
			role := strings.TrimSpace(link.Role)
			if role != "" && !allowedLinkRoles[role] {
				report.addError("invalid_link_role", unit.ID, unit.File, fmt.Sprintf("link role %q is not allowed", role))
			}
			resolved := p.resolveLink(unit, link)
			switch resolved.Status {
			case "missing":
				report.addWarning("missing_link", unit.ID, unit.File, fmt.Sprintf("link %q does not exist", resolved.Path))
			case "invalid":
				report.addError("invalid_link", unit.ID, unit.File, fmt.Sprintf("link %q is invalid", resolved.Path))
			}
			if filepath.IsAbs(resolved.Path) {
				report.addWarning("absolute_link_path", unit.ID, unit.File, fmt.Sprintf("link %q is absolute and reduces portability", resolved.Path))
			}
		}
		if unit.Refines != "" {
			if _, ok := p.ByID[unit.Refines]; !ok {
				report.addError("missing_refines", unit.ID, unit.File, fmt.Sprintf("refines references missing GSP %q", unit.Refines))
			}
		}
		if unit.Context == "" {
			report.addNotice("placeholder", unit.ID, unit.File, "GSP has no context and is treated as placeholder")
		}
		p.validateCustomFields(&report, unit)
	}
	for id, units := range p.Duplicates {
		files := make([]string, 0, len(units))
		seen := map[string]bool{}
		for _, unit := range units {
			if !seen[unit.File] {
				files = append(files, unit.File)
				seen[unit.File] = true
			}
		}
		sort.Strings(files)
		report.addError("duplicate_id", id, "", fmt.Sprintf("id %q is defined more than once: %v", id, files))
	}
	if stage != "" {
		stageReport := p.StageCheck(stage)
		report.Errors = append(report.Errors, stageReport.Errors...)
		report.Warnings = append(report.Warnings, stageReport.Warnings...)
		if len(stageReport.Errors) > 0 {
			report.OK = false
		}
	}
	return report
}

func (p *Project) Index() []IndexEntry {
	entries := make([]IndexEntry, 0, len(p.Units))
	for _, unit := range p.Units {
		with := make([]string, 0, len(unit.With))
		for _, rel := range unit.With {
			with = append(with, rel.ID)
		}
		links := make([]string, 0, len(unit.Links))
		for _, link := range unit.Links {
			links = append(links, link.Path)
		}
		sort.Strings(with)
		sort.Strings(links)
		entries = append(entries, IndexEntry{
			ID:         unit.ID,
			Title:      unit.Title,
			File:       unit.File,
			Type:       unit.Type,
			Resolution: unit.Resolution,
			With:       with,
			Refines:    unit.Refines,
			Links:      links,
		})
	}
	sort.Slice(entries, func(i, j int) bool {
		return entries[i].ID < entries[j].ID
	})
	return entries
}

var defaultStageRules = map[string]string{
	"design":    "L0",
	"integrate": "L2",
	"implement": "L3",
	"bind":      "L4",
	"release":   "L5",
}

func (p *Project) StageCheck(stage string) Report {
	report := Report{OK: true}
	required, ok := p.Manifest.minResolution(stage)
	if !ok {
		report.addError("unknown_stage", "", "", fmt.Sprintf("unknown stage %q", stage))
		return report
	}
	minRank, _ := resolutionValue(required)
	for _, unit := range p.Units {
		rank, ok := resolutionValue(unit.Resolution)
		if !ok {
			report.addError("invalid_resolution", unit.ID, unit.File, fmt.Sprintf("resolution %q is not allowed", unit.Resolution))
			continue
		}
		if rank < minRank {
			report.addError("low_resolution", unit.ID, unit.File, fmt.Sprintf("resolution %s is below %s for stage %s", displayResolution(unit.Resolution), required, stage))
		}
	}
	if len(report.Errors) == 0 {
		report.OK = true
	}
	return report
}

func displayResolution(value string) string {
	if value == "" {
		return "L0"
	}
	return value
}

func (p *Project) Trace(id string, depth int, filter Filter) TraceResult {
	flatten := p.Flatten(id, depth, filter)
	graph := p.graphForUnits(flatten.Units)
	return TraceResult{
		Entry:    id,
		Depth:    depth,
		Nodes:    flatten.Units,
		Edges:    graph.Edges,
		Warnings: flatten.Warnings,
	}
}

func (p *Project) Flatten(id string, depth int, filter Filter) FlattenResult {
	walker := &walker{
		project: p,
		depth:   depth,
		filter:  filter,
		seen:    map[string]bool{},
		stack:   map[string]bool{},
	}
	walker.visit(id, 0)
	return FlattenResult{
		Entry:    id,
		Depth:    depth,
		Units:    walker.units,
		Warnings: walker.warnings,
	}
}

func (p *Project) Pack(id string, depth, budget int, filter Filter) PackResult {
	return p.PackFor(id, "", "", depth, budget, filter)
}

func (p *Project) PackFor(id, intent, stage string, depth, budget int, filter Filter) PackResult {
	flattened := p.Flatten(id, depth, filter)
	units := make([]*Unit, 0, len(flattened.Units))
	approx := 0
	truncated := false
	for _, unit := range flattened.Units {
		candidate := append(units, unit)
		data, _ := json.Marshal(candidate)
		if budget > 0 && len(data) > budget && len(units) > 0 {
			truncated = true
			break
		}
		units = candidate
		approx = len(data)
	}
	links := p.resolveLinks(units)
	return PackResult{
		Entry:       id,
		Intent:      intent,
		Stage:       stage,
		Depth:       depth,
		Budget:      budget,
		Truncated:   truncated,
		Units:       units,
		Links:       links,
		Summary:     summarizeUnits(units, len(flattened.Warnings), len(links)),
		ApproxChars: approx,
		Warnings:    flattened.Warnings,
	}
}

func summarizeUnits(units []*Unit, missingCount, linkCount int) Summary {
	summary := Summary{
		UnitCount:    len(units),
		TypeCounts:   map[string]int{},
		MissingCount: missingCount,
		LinkCount:    linkCount,
	}
	min := 99
	max := -1
	for _, unit := range units {
		if unit.Type != "" {
			summary.TypeCounts[unit.Type]++
		}
		rank, ok := resolutionValue(unit.Resolution)
		if !ok {
			continue
		}
		if rank < min {
			min = rank
			summary.MinResolution = displayResolution(unit.Resolution)
		}
		if rank > max {
			max = rank
			summary.MaxResolution = displayResolution(unit.Resolution)
		}
	}
	if len(summary.TypeCounts) == 0 {
		summary.TypeCounts = nil
	}
	return summary
}

func (p *Project) Impact(id string, depth int) ImpactResult {
	result := ImpactResult{Entry: id, Depth: depth}
	if _, ok := p.ByID[id]; !ok {
		result.Warnings = append(result.Warnings, Issue{Level: "warning", Code: "missing", ID: id, Message: fmt.Sprintf("missing GSP %q", id)})
		return result
	}

	reverse := map[string][]ImpactEntry{}
	for _, unit := range p.Units {
		if unit.Refines != "" {
			reverse[unit.Refines] = append(reverse[unit.Refines], impactEntry(unit, 0, unit.Refines, "refines"))
		}
		for _, rel := range unit.With {
			reverse[rel.ID] = append(reverse[rel.ID], impactEntry(unit, 0, rel.ID, "with"))
		}
	}
	for key := range reverse {
		sort.Slice(reverse[key], func(i, j int) bool {
			return reverse[key][i].ID < reverse[key][j].ID
		})
	}

	seen := map[string]bool{id: true}
	queue := []ImpactEntry{{ID: id, Depth: 0}}
	for len(queue) > 0 {
		current := queue[0]
		queue = queue[1:]
		if depth >= 0 && current.Depth >= depth {
			continue
		}
		for _, affected := range reverse[current.ID] {
			if seen[affected.ID] {
				continue
			}
			seen[affected.ID] = true
			affected.Depth = current.Depth + 1
			affected.Via = current.ID
			if affected.Depth == 1 {
				result.Direct = append(result.Direct, affected)
			} else {
				result.Indirect = append(result.Indirect, affected)
			}
			result.Edges = append(result.Edges, GraphEdge{From: affected.ID, To: current.ID, Kind: affected.Kind})
			queue = append(queue, affected)
			if affected.Depth > result.Summary.MaxDepth {
				result.Summary.MaxDepth = affected.Depth
			}
		}
	}
	sortImpactEntries(result.Direct)
	sortImpactEntries(result.Indirect)
	sort.Slice(result.Edges, func(i, j int) bool {
		return strings.Join([]string{result.Edges[i].From, result.Edges[i].To, result.Edges[i].Kind}, "\x00") < strings.Join([]string{result.Edges[j].From, result.Edges[j].To, result.Edges[j].Kind}, "\x00")
	})
	result.Summary.DirectCount = len(result.Direct)
	result.Summary.IndirectCount = len(result.Indirect)
	result.Summary.TotalCount = len(result.Direct) + len(result.Indirect)
	return result
}

func impactEntry(unit *Unit, depth int, via, kind string) ImpactEntry {
	return ImpactEntry{
		ID:         unit.ID,
		Title:      unit.Title,
		Type:       unit.Type,
		Resolution: unit.Resolution,
		File:       unit.File,
		Depth:      depth,
		Via:        via,
		Kind:       kind,
	}
}

func sortImpactEntries(entries []ImpactEntry) {
	sort.Slice(entries, func(i, j int) bool {
		if entries[i].Depth == entries[j].Depth {
			return entries[i].ID < entries[j].ID
		}
		return entries[i].Depth < entries[j].Depth
	})
}

type walker struct {
	project  *Project
	depth    int
	filter   Filter
	seen     map[string]bool
	stack    map[string]bool
	units    []*Unit
	warnings []Issue
}

func (w *walker) visit(id string, currentDepth int) {
	if w.depth >= 0 && currentDepth > w.depth {
		return
	}
	if w.stack[id] {
		w.warnings = append(w.warnings, Issue{Level: "warning", Code: "cycle", ID: id, Message: fmt.Sprintf("cycle detected at %q", id)})
		return
	}
	unit, ok := w.project.ByID[id]
	if !ok {
		w.warnings = append(w.warnings, Issue{Level: "warning", Code: "missing", ID: id, Message: fmt.Sprintf("missing GSP %q", id)})
		return
	}
	if w.seen[id] {
		return
	}
	w.seen[id] = true
	if currentDepth == 0 || w.filter.Allows(unit) {
		w.units = append(w.units, unit)
	}
	w.stack[id] = true
	if unit.Refines != "" {
		w.visit(unit.Refines, currentDepth+1)
	}
	withIDs := make([]string, 0, len(unit.With))
	for _, rel := range unit.With {
		withIDs = append(withIDs, rel.ID)
	}
	sort.Strings(withIDs)
	for _, relID := range withIDs {
		w.visit(relID, currentDepth+1)
	}
	delete(w.stack, id)
}