package gsp

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

func (p *Project) Validate(stage string) Report {
	report := Report{OK: true}
	for _, issue := range p.LoadIssues {
		report.Errors = append(report.Errors, issue)
		report.OK = false
	}
	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))
			}
		}
		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")
		}
	}
	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)
		}
		sort.Strings(with)
		entries = append(entries, IndexEntry{
			ID:         unit.ID,
			File:       unit.File,
			Type:       unit.Type,
			Resolution: unit.Resolution,
			With:       with,
			Refines:    unit.Refines,
		})
	}
	sort.Slice(entries, func(i, j int) bool {
		return entries[i].ID < entries[j].ID
	})
	return entries
}

func (p *Project) StageCheck(stage string) Report {
	report := Report{OK: true}
	required, ok := map[string]string{
		"design":    "L0",
		"integrate": "L2",
		"implement": "L3",
		"bind":      "L4",
		"release":   "L5",
	}[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 {
	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)
	}
	return PackResult{
		Entry:       id,
		Depth:       depth,
		Budget:      budget,
		Truncated:   truncated,
		Units:       units,
		ApproxChars: approx,
		Warnings:    flattened.Warnings,
	}
}

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)
}