From 0f19fa71be77deba4a9dee1db9e5685893540936 Mon Sep 17 00:00:00 2001
From: SinusFox <61253950+SinusFox@users.noreply.github.com>
Date: Fri, 11 Oct 2024 16:08:24 +0200
Subject: [PATCH] Adding MPS Export (#31)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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* Initial Push

Inititial project state

* Static demo version

* static demo site - added variables

a

* first_implementation

* Updated UI, Improved Style to be more "Reactly", added Functionality

* add parsing functions

* change folder

* Import/Export Prototype

* Adding "reactjs-popup" to package,json

* Adding GLPK source

* Rough implementation of solver + example

* Show solution in output

* example 2 + popup lib

* removing import button

This feature won't be needed in this state of the project and might come back later. Right now it serves no functional purpose.

* Removing "Popout" button

This feature won't be needed in this state of the project and might come back later. Right now it serves no functional purpose.

* Updating Logs

Now the site displays all logs created with customLog(STRING). Logs can be cleared with customLogClear();

* Adding walltime

Can be called using:

Start:
function walltimeStart() {
returns Date.now();

Stop:
function walltimeStopAndPrint(startpoint: number) {
Add startpoint as argument.
It prints the elapsed time using customLog()

* Adding duals ouput

* Adding glpk.js package

required dependency

* adding LP format export and fixing a few errors

* fixing further errors

* adding automatic build

* Moving files to correct folders

* Update nextjs.yml

* Updating README and .gitignore

README:
- added installation instructions
- added troubleshooting

gitignore:
- skipping Writerside and .idea folders

* Update LICENCE.txt

We are required to use the same license. See https://github.com/hgourvest/node-glpk/blob/master/LICENSE

* Updating icon

* Adding RegEx input checks and updating text box explanations

* Update README.md

Updating license info

Signed-off-by: SinusFox <61253950+SinusFox@users.noreply.github.com>

* Deleting license to recreate proper license

* Update layout.tsx

fixing typo

Signed-off-by: SinusFox <61253950+SinusFox@users.noreply.github.com>

* Fixing word issue

English has some false friends... like the German "Enter" is actually return in English.

* Updatint License

* Fixing design issue and updating license link

* Fixing typo in log

* Fixing white mode

* adding translations 1/2

UI Translations

Coming in 2/2: Output translations

* adding output translations

* adding minimize button

* adding unit test for rendering home page

* fixing maxmin on lp export

* Update .gitignore

* Update .gitignore

* Update scripts.ts

* Update scripts.ts

* Update README.md

* adding tests

* Adding MPS Export

* Updating language file

* Updating Deployment Structure/GitHub Actions

* Update nextjsbuildonly.yml

---------

Signed-off-by: SinusFox <61253950+SinusFox@users.noreply.github.com>
Co-authored-by: moebiusl <lucas.moebius@icloud.com>
Co-authored-by: Marcel Pöppe <marcel.poeppe@gmail.com>
---
 .github/workflows/nextjs.yml          |   3 -
 .github/workflows/nextjsbuildonly.yml |  62 ++++
 src/app/lang.ts                       |  12 +
 src/app/page.tsx                      |   7 +-
 src/app/scripts.ts                    | 408 +++++++++++++++++++++++++-
 src/solver/jvail/Bound.tsx            |   6 +
 src/solver/jvail/Bounds.tsx           |   9 +
 src/solver/jvail/Constraint.tsx       |   8 +
 src/solver/jvail/LP.tsx               |  18 ++
 src/solver/jvail/Options.tsx          |  12 +
 src/solver/jvail/Result.tsx           |  10 +
 src/solver/jvail/Variable.tsx         |   4 +
 12 files changed, 543 insertions(+), 16 deletions(-)
 create mode 100644 .github/workflows/nextjsbuildonly.yml
 create mode 100644 src/solver/jvail/Bound.tsx
 create mode 100644 src/solver/jvail/Bounds.tsx
 create mode 100644 src/solver/jvail/Constraint.tsx
 create mode 100644 src/solver/jvail/LP.tsx
 create mode 100644 src/solver/jvail/Options.tsx
 create mode 100644 src/solver/jvail/Result.tsx
 create mode 100644 src/solver/jvail/Variable.tsx

diff --git a/.github/workflows/nextjs.yml b/.github/workflows/nextjs.yml
index f292803..b092bac 100644
--- a/.github/workflows/nextjs.yml
+++ b/.github/workflows/nextjs.yml
@@ -11,9 +11,6 @@ on:
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
-  
-  # Automatically run on Pull Request
-  pull_request:
 
 # Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
 permissions:
diff --git a/.github/workflows/nextjsbuildonly.yml b/.github/workflows/nextjsbuildonly.yml
new file mode 100644
index 0000000..11137fb
--- /dev/null
+++ b/.github/workflows/nextjsbuildonly.yml
@@ -0,0 +1,62 @@
+# Sample workflow for building and deploying a Next.js site to GitHub Pages
+#
+# To get started with Next.js see: https://nextjs.org/docs/getting-started
+#
+name: Build Next.js site
+
+on:
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+  
+  # Automatically run on Pull Request
+  pull_request:
+
+# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
+# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  # Build job
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Detect package manager
+        id: detect-package-manager
+        run: |
+          if [ -f "${{ github.workspace }}/yarn.lock" ]; then
+            echo "manager=yarn" >> $GITHUB_OUTPUT
+            echo "command=install" >> $GITHUB_OUTPUT
+            echo "runner=yarn" >> $GITHUB_OUTPUT
+            exit 0
+          elif [ -f "${{ github.workspace }}/package.json" ]; then
+            echo "manager=npm" >> $GITHUB_OUTPUT
+            echo "command=ci" >> $GITHUB_OUTPUT
+            echo "runner=npx --no-install" >> $GITHUB_OUTPUT
+            exit 0
+          else
+            echo "Unable to determine package manager"
+            exit 1
+          fi
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+          cache: ${{ steps.detect-package-manager.outputs.manager }}
+      - name: Restore cache
+        uses: actions/cache@v4
+        with:
+          path: |
+            .next/cache
+          # Generate a new cache whenever packages or source files change.
+          key: ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/yarn.lock') }}-${{ hashFiles('**.[jt]s', '**.[jt]sx') }}
+          # If source files changed but packages didn't, rebuild from a prior cache.
+          restore-keys: |
+            ${{ runner.os }}-nextjs-${{ hashFiles('**/package-lock.json', '**/yarn.lock') }}-
+      - name: Install dependencies
+        run: ${{ steps.detect-package-manager.outputs.manager }} ${{ steps.detect-package-manager.outputs.command }}
+      - name: Build with Next.js
+        run: ${{ steps.detect-package-manager.outputs.runner }} next build
diff --git a/src/app/lang.ts b/src/app/lang.ts
index 4b1f2d1..c61f566 100644
--- a/src/app/lang.ts
+++ b/src/app/lang.ts
@@ -24,6 +24,8 @@ export default function text(lang: string, input: string): string {
                     return "Listen Sie alle Ihre Variablen auf. Eine pro Zeile (mit der 'Enter'-Taste trennen). Erlaubte Symbole sind a-z, A-Z.\nBeispiel:\nx\ny";
                 case "boxExportLP":
                     return "Als LP exportieren";
+                case "boxExportMPS":
+                    return "Als MPS exportieren";
                 case "boxOut":
                     return "Geben Sie ein Problem ein und drücken Sie eine Aktionstaste, um die Ausgabe anzuzeigen...";
                 case "buttonCalc":
@@ -92,8 +94,12 @@ export default function text(lang: string, input: string): string {
                     return "Download wird vorbereitet...";
                 case "downloadFetchInput":
                     return "Eingaben werden geladen...";
+                case "downloadCheckInput":
+                    return "Überprüfe auf leere Eingabefelder...";
                 case "importing":
                     return "Importiere...";
+                case "err_invalidConstraintFormat":
+                    return "Fehler: Nicht erlaubter Operator verwendet.";
             default:
                 return input;
         }
@@ -125,6 +131,8 @@ export default function text(lang: string, input: string): string {
                 return "List all your variables. One per line (divide by 'return' button). Allowed symbols are a-z, A-Z.\nExample:\nx\ny";
             case "boxExportLP":
                 return "Export as LP";
+            case "boxExportMPS":
+                return "Export as MPS";
             case "boxOut":
                 return "Input a problem and an action button to display output...";
             case "buttonCalc":
@@ -193,8 +201,12 @@ export default function text(lang: string, input: string): string {
                 return "Preparing download...";
             case "downloadFetchInput":
                 return "Fetching input...";
+            case "downloadCheckInput":
+                return "Checking for empty input boxes...";
             case "importing":
                 return "Importing...";
+            case "err_invalidConstraintFormat":
+                return "Error: Invalid constraint format.";
             default:
                 return input;
         }
diff --git a/src/app/page.tsx b/src/app/page.tsx
index 332c116..b321e2e 100644
--- a/src/app/page.tsx
+++ b/src/app/page.tsx
@@ -2,7 +2,7 @@
 
 import React, { useState } from 'react';
 import { Box, Button, Output } from "./modules";
-import { calculate_click, downloadLP } from "./scripts";
+import { calculate_click, downloadLP, downloadMPS } from "./scripts";
 import text from "./lang";
 
 export default function Home() {
@@ -24,6 +24,7 @@ export default function Home() {
   const tr_calc_max = text(language, "maximize");
   const tr_calc_min = text(language, "minimize");
   const tr_calcButton = text(language, "buttonCalc");
+  const tr_boxExportMPS = text(language, "boxExportMPS");
 
   const handleLanguageChange = (event: React.ChangeEvent<HTMLSelectElement>) => {
     setLanguage(event.target.value);
@@ -85,6 +86,10 @@ export default function Home() {
         className={"button"}
         onClickFunc={downloadLP}
       />
+      <Button
+        title={tr_boxExportMPS}
+        className={"button"}
+        onClickFunc={downloadMPS} />
       <br />
       <Output
         id="out"
diff --git a/src/app/scripts.ts b/src/app/scripts.ts
index d01f4a7..a39ebc4 100644
--- a/src/app/scripts.ts
+++ b/src/app/scripts.ts
@@ -1,7 +1,7 @@
-import * as MIP from "../parser/parseMIP"
-import * as LP from "../parser/parseLP"
-import * as LPAPI from "../api/optimizeLP.js"
-
+import { LP } from "../solver/jvail/LP";
+import { Bound } from "../solver/jvail/Bound";
+import { Variable } from "../solver/jvail/Variable";
+import { Bounds, GLP_MAX, GLP_MIN, GLP_UP, GLP_LO, GLP_FX, GLP_FR, GLP_DB } from "../solver/jvail/Bounds";
 import * as GLPKAPI from "../solver/glpk.min.js"
 import { start } from "repl";
 
@@ -109,6 +109,30 @@ export function isInputValidRegex(obj: string | undefined, subj: string | undefi
 }
 
 export function isInputFilled(obj: string | undefined, subj: string | undefined, bounds: string | undefined, vars: string | undefined): boolean {
+  // if empty input: fetching inputs
+  if (obj == "" || subj == "" || bounds == "" || vars == "") {
+    const objectiveElement = document.getElementById('objective');
+    if (objectiveElement !== null) {
+      obj = (objectiveElement as HTMLInputElement).value;
+    }
+
+    const subjectElement = document.getElementById('subject');
+    if (subjectElement !== null) {
+      subj = (subjectElement as HTMLInputElement).value;
+    }
+
+
+    const boundsElement = document.getElementById('bounds');
+    if (boundsElement !== null) {
+      bounds = (boundsElement as HTMLInputElement).value;
+    }
+
+    const varsElement = document.getElementById('vars');
+    if (varsElement !== null) {
+      vars = (varsElement as HTMLInputElement).value;
+    }
+  }
+  
   if (obj == "" || obj == null || obj == undefined) {
     customLog("err_emptyBox");
     return false;
@@ -238,7 +262,7 @@ export function downloadLPFormatting(objective: any, subject: any, bounds: any)
   let operator = "Minimize";
   if (maxmin == "maximize") operator = "Maximize";
 
-  // Header mit Problemname
+  // Header with problem name
   const header = "\\ Your problem\n";
 
   //  format objective
@@ -271,9 +295,19 @@ export function downloadLP() {
   customLogClear();
   customLog("downloadPrep");
   customLog("");
-  customLog("downloadFetchInput");
+  customLog("downloadCheckInput");
   customLog("");
 
+  if (!isInputFilled("","","","")) return;
+
+  let exportString: string | undefined = getInputsForLPAsString();
+
+  if (exportString === undefined) return;
+
+  downloadProblemDownload(exportString);
+}
+
+function getInputsForLP() {
   let objective: string | undefined;
   const objectiveElement = document.getElementById('objective');
   if (objectiveElement !== null) {
@@ -298,10 +332,360 @@ export function downloadLP() {
     variables = (varsElement as HTMLInputElement).value;
   }
 
-  // catch error: empty input field(s)
-  if (!isInputFilled(objective, subject, bounds, variables)) return;
-
-  const exportString: string = downloadLPFormatting(objective, subject, bounds);
-
-  downloadProblemDownload(exportString);
+  return { objective, subject, bounds };
+}
+
+function getInputsForLPAsString(): string {
+
+  let inputs = getInputsForLP();
+  let obj = inputs?.objective;
+  let sub = inputs?.subject;
+  let bnds = inputs?.bounds;
+
+  const exportString: string = downloadLPFormatting(obj, sub, bnds);
+
+  return exportString;
+}
+
+export function convertLPToMPS(lp: LP): string {
+  let mpsString = '';
+
+  // NAME section
+  mpsString += `NAME          ${lp.name}\n`;
+
+  // ROWS section
+  mpsString += 'ROWS\n';
+  mpsString += ` N  ${lp.objective.name}\n`; // Objective row
+  lp.subjectTo.forEach(constraint => {
+    if (constraint.bounds.type === GLP_UP) { // <=
+      mpsString += ` L  ${constraint.name}\n`;
+    } else if (constraint.bounds.type === GLP_LO) { // >=
+      mpsString += ` G  ${constraint.name}\n`;
+    } else if (constraint.bounds.type === GLP_FX) { // =
+      mpsString += ` E  ${constraint.name}\n`;
+    }
+  });
+
+  // COLUMNS section
+  mpsString += 'COLUMNS\n';
+  const variableMap: { [key: string]: { row: string; coef: number }[] } = {};
+  lp.objective.vars.forEach(varObj => {
+    if (!variableMap[varObj.name]) {
+      variableMap[varObj.name] = [];
+    }
+    variableMap[varObj.name].push({ row: lp.objective.name, coef: varObj.coef });
+  });
+  lp.subjectTo.forEach(constraint => {
+    constraint.vars.forEach(varObj => {
+      if (!variableMap[varObj.name]) {
+        variableMap[varObj.name] = [];
+      }
+      variableMap[varObj.name].push({ row: constraint.name, coef: varObj.coef });
+    });
+  });
+
+  for (const [variable, rows] of Object.entries(variableMap)) {
+    rows.forEach(entry => {
+      mpsString += `    ${variable}  ${entry.row}  ${entry.coef}\n`;
+    });
+  }
+
+  // RHS section
+  mpsString += 'RHS\n';
+  lp.subjectTo.forEach(constraint => {
+    if (constraint.bounds.type === GLP_UP) { // <= or =
+      mpsString += `    RHS1  ${constraint.name}  ${constraint.bounds.ub}\n`;
+    } else if (constraint.bounds.type === GLP_LO || constraint.bounds.type === GLP_FX) { // >=
+      mpsString += `    RHS1  ${constraint.name}  ${constraint.bounds.lb}\n`;
+    }
+  });
+
+  // BOUNDS section
+  if (lp.bounds && lp.bounds.length > 0) {
+    mpsString += 'BOUNDS\n';
+    lp.bounds.forEach(bound => {
+      if (bound.lb !== -Infinity) {
+        mpsString += ` LO BND1  ${bound.name}  ${bound.lb}\n`;
+      }
+      if (bound.ub !== Infinity) {
+        mpsString += ` UP BND1  ${bound.name}  ${bound.ub}\n`;
+      }
+    });
+  }
+
+  // BINARY section
+  if (lp.binaries && lp.binaries.length > 0) {
+    mpsString += 'BINARY\n';
+    lp.binaries.forEach(bin => {
+      mpsString += `    ${bin}\n`;
+    });
+  }
+
+  // GENERAL section
+  if (lp.generals && lp.generals.length > 0) {
+    mpsString += 'GENERAL\n';
+    lp.generals.forEach(gen => {
+      mpsString += `    ${gen}\n`;
+    });
+  }
+
+  // ENDATA section
+  mpsString += 'ENDATA\n';
+
+  return mpsString;
+}
+
+// read LP format from string
+function parseLP(lpString: string): LP {
+  const lines = lpString.split("\n").map((line) => line.trim()).filter((line) => line.length > 0);
+  let mode: string = '';
+  let lp: LP = {
+    name: '',
+    objective: {
+      direction: GLP_MAX, // 1 for maximize, -1 for minimize
+      name: '',
+      vars: []
+    },
+    subjectTo: [],
+    bounds: [],
+    binaries: [],
+    generals: []
+  };
+
+  let objectiveExpression = '';
+  let constraintExpression = '';
+  let currentConstraintName = '';
+
+  for (let line of lines) {
+
+    // handle each block differently
+    // set mode for each to determine parsing path
+    if (line.startsWith("Maximize")) {
+      lp.objective.direction = GLP_MAX;
+      mode = 'objective';
+      continue;
+    } else if (line.startsWith("Minimize")) {
+      lp.objective.direction = GLP_MIN;
+      mode = 'objective';
+      continue;
+    } else if (line.startsWith("Subject To")) {
+      // Constraint section
+      if (objectiveExpression.length > 0) {
+        lp.objective.vars = parseLPExpression(objectiveExpression.trim());
+        objectiveExpression = '';
+      }
+      mode = 'subjectTo';
+      continue;
+    } else if (line.startsWith("Bounds")) {
+      // Bound section
+      if (constraintExpression.length > 0 && currentConstraintName.length > 0) {
+        const { vars, bound } = parseLPConstraint(constraintExpression.trim());
+        lp.subjectTo.push({
+          name: currentConstraintName,
+          vars: vars,
+          bounds: bound
+        });
+        constraintExpression = '';
+        currentConstraintName = '';
+      }
+      mode = 'bounds';
+      continue;
+    } else if (line.startsWith("Binary")) {
+      mode = 'binaries';
+      continue;
+    } else if (line.startsWith("General")) {
+      mode = 'generals';
+      continue;
+    } else if (line.startsWith("End")) {
+      mode = 'end';
+      continue;
+    }
+
+    // Parse based on current mode
+    if (mode === 'objective') {
+      const splitLine = line.split(":");
+      if (splitLine.length === 2) {
+        lp.objective.name = splitLine[0].trim(); // if name in first line
+        objectiveExpression += splitLine[1].trim() + ' ';
+      } else {
+        objectiveExpression += line.trim() + ' '; // multiline expansion of objective
+      }
+
+    } else if (mode === 'subjectTo') {
+      const splitLine = line.split(":");
+      if (splitLine.length === 2) {
+        if (constraintExpression.length > 0 && currentConstraintName.length > 0) {
+          // new Constraint -> add previous to the subjects
+          const { vars, bound } = parseLPConstraint(constraintExpression.trim());
+          lp.subjectTo.push({
+            name: currentConstraintName,
+            vars: vars,
+            bounds: bound
+          });
+        }
+        // start collecting the new constraint
+        currentConstraintName = splitLine[0].trim();
+        constraintExpression = splitLine[1].trim() + ' ';
+      } else {
+        // continue collecting the expression if it's multi-line
+        constraintExpression += line.trim() + ' ';
+      }
+    } else if (mode === 'bounds') {
+      const bound = parseLPBound(line.trim());
+      if (bound && lp.bounds) {
+        lp.bounds.push(bound);
+      }
+    } else if (mode === 'binaries') {
+      lp.binaries?.push(line.trim());
+    } else if (mode === 'generals') {
+      lp.generals?.push(line.trim());
+    }
+  }
+
+  // if no "subject to" previously, do it here
+  if (objectiveExpression.length > 0) {
+    lp.objective.vars = parseLPExpression(objectiveExpression.trim());
+  }
+
+  // same for "bounds" and "end"
+  if (constraintExpression.length > 0 && currentConstraintName.length > 0) {
+    const { vars, bound } = parseLPConstraint(constraintExpression.trim());
+    lp.subjectTo.push({
+      name: currentConstraintName,
+      vars: vars,
+      bounds: bound
+    });
+  }
+
+  return lp;
+}
+
+// Helper for expressions
+function parseLPExpression(expr: string): Variable[] {
+  const regex = /([+-]?\s*\d*\.?\d*)\s*([a-zA-Z_][a-zA-Z_0-9]*)/g;
+  let match;
+  let vars: Variable[] = [];
+
+  // loop over all variables in expresion
+  while ((match = regex.exec(expr)) !== null) {
+    let temp_coef = match[1].replace(/\s+/g, '').trim() || '1';
+    temp_coef = temp_coef === "-" || temp_coef === '+' ? `${temp_coef}1` : temp_coef;
+    const coef = parseFloat(temp_coef);
+    const name = match[2];
+    vars.push({ name: name, coef: coef });
+  }
+
+  return vars;
+}
+
+// Helper for Constraint section
+function parseLPConstraint(constraint: string): { vars: Variable[], bound: Bounds } {
+  // Valid operators in Constraints
+  const operators = ["<=", ">=", "="];
+  let operator = operators.find(op => constraint.includes(op));
+  if (!operator) {
+    throw new Error(getTranslation("err_invalidConstraintFormat"));
+  }
+
+  const [expr, boundStr] = constraint.split(operator);
+  const vars: Variable[] = parseLPExpression(expr.trim());
+  const boundValue = parseFloat(boundStr.trim());
+
+  // determine bound type
+  let boundType = GLP_UP;
+  if (operator === "<=") {
+    boundType = GLP_UP;
+  } else if (operator === ">=") {
+    boundType = GLP_LO;
+  } else if (operator === "=") {
+    boundType = GLP_FX;
+  }
+  let lb = boundType === GLP_FX ? boundValue : boundType === GLP_LO ? boundValue : -Infinity;
+  let ub = boundType === GLP_UP ? boundValue : Infinity;
+
+  const bound: Bounds = {
+    type: boundType,
+    lb: lb,
+    ub: ub
+  } as Bounds;
+
+  return { vars, bound };
+}
+
+// Helper for Bound section
+function parseLPBound(boundStr: string): Bound | null {
+  // Regex to handle various bound formats
+  const regex = /^([-]?\d*\.?\d*)?\s*(<=|>=|=)?\s*([a-zA-Z_][a-zA-Z_0-9]*)\s*(<=|>=|=)?\s*([-]?\d*\.?\d*)?$/;
+  const match = regex.exec(boundStr.trim());
+
+  if (match) {
+    const [, lbStr, leftOperator, varName, rightOperator, ubStr] = match;
+    let lb = lbStr ? parseFloat(lbStr) : undefined;
+    let ub = ubStr ? parseFloat(ubStr) : undefined;
+    let type: number;
+
+    // Handle free "edgecase"
+    if (boundStr.toLowerCase().includes('free')) {
+      return {
+        type: GLP_FR,
+        name: varName,
+        lb: -Infinity,
+        ub: Infinity
+      } as Bound;
+    }
+
+    // Determine bound type
+    if (leftOperator && rightOperator) {
+      if (leftOperator === '<=' && rightOperator === '<=') {
+        type = GLP_DB; // Double bound
+      } else if (leftOperator === '>=' && rightOperator === '>=') {
+        type = GLP_DB; // Double bound (reverse order)
+        [lb, ub] = [ub, lb]; // Swap lb and ub
+      } else {
+        return null; // Invalid combination
+      }
+      // detect one-sided bounds
+    } else if (leftOperator === '<=') {
+      type = GLP_UP;
+      ub = lb;
+      lb = undefined;
+    } else if (rightOperator === '<=') {
+      type = GLP_UP;
+    } else if (leftOperator === '>=') {
+      type = GLP_LO;
+    } else if (rightOperator === '>=') {
+      type = GLP_LO;
+      lb = ub;
+      ub = undefined;
+    } else if (leftOperator === '=' || rightOperator === '=') {
+      type = GLP_FX;
+      if (leftOperator === '=') ub = lb;
+      else lb = ub;
+    } else {
+      type = GLP_FR; // No bounds specified, assume free
+    }
+
+    return {
+      type,
+      name: varName,
+      lb: lb !== undefined ? lb : -Infinity,
+      ub: ub !== undefined ? ub : Infinity
+    } as Bound;
+  }
+  return null;
+}
+
+export function downloadMPS() {
+  customLogClear();
+  customLog("downloadPrep");
+  customLog("");
+  customLog("downloadCheckInput");
+  customLog("");
+  if (!isInputFilled("","","","")) return;
+
+  let inputs = getInputsForLPAsString();
+  let lp = parseLP(inputs);
+  let mps = convertLPToMPS(lp);
+
+  downloadProblemDownload(mps);
 }
diff --git a/src/solver/jvail/Bound.tsx b/src/solver/jvail/Bound.tsx
new file mode 100644
index 0000000..70c905d
--- /dev/null
+++ b/src/solver/jvail/Bound.tsx
@@ -0,0 +1,6 @@
+export interface Bound{
+    name: string;
+    type: number; // 1 for lower bound, 2 for upper bound, 3 for equal
+    ub: number;
+    lb: number;
+}
\ No newline at end of file
diff --git a/src/solver/jvail/Bounds.tsx b/src/solver/jvail/Bounds.tsx
new file mode 100644
index 0000000..0b8ed75
--- /dev/null
+++ b/src/solver/jvail/Bounds.tsx
@@ -0,0 +1,9 @@
+export interface Bounds{ type: number, ub: number, lb: number }
+
+export const GLP_FR = 1;  /* free (unbounded) variable */
+export const GLP_LO = 2;  /* variable with lower bound */
+export const GLP_UP = 3;  /* variable with upper bound */
+export const GLP_DB = 4;  /* double-bounded variable */
+export const GLP_FX = 5;  /* fixed variable */
+export const GLP_MAX = 2;
+export const GLP_MIN = 1
\ No newline at end of file
diff --git a/src/solver/jvail/Constraint.tsx b/src/solver/jvail/Constraint.tsx
new file mode 100644
index 0000000..70bc38b
--- /dev/null
+++ b/src/solver/jvail/Constraint.tsx
@@ -0,0 +1,8 @@
+import {Variable} from "./Variable";
+import {Bounds} from "./Bounds";
+
+export interface Constraint {
+    name: string;
+    vars: Variable[];
+    bounds: Bounds;
+}
\ No newline at end of file
diff --git a/src/solver/jvail/LP.tsx b/src/solver/jvail/LP.tsx
new file mode 100644
index 0000000..7109fe5
--- /dev/null
+++ b/src/solver/jvail/LP.tsx
@@ -0,0 +1,18 @@
+import {Variable} from "./Variable";
+import {Bound} from "./Bound";
+import {Options} from "./Options";
+import {Constraint} from "./Constraint";
+
+export interface LP {
+    name: string,
+    objective: {
+        direction: number,
+        name: string,
+        vars: Variable[]
+    },
+    subjectTo: Constraint[],
+    bounds?: Bound[],
+    binaries?: string[],
+    generals?: string[],
+    options?: Options
+}
\ No newline at end of file
diff --git a/src/solver/jvail/Options.tsx b/src/solver/jvail/Options.tsx
new file mode 100644
index 0000000..311b22a
--- /dev/null
+++ b/src/solver/jvail/Options.tsx
@@ -0,0 +1,12 @@
+import {Result} from "./Result";
+
+export interface Options {
+    mipgap?: number,    /* set relative mip gap tolerance to mipgap, default 0.0 */
+    tmlim?: number,     /* limit solution time to tmlim seconds, default INT_MAX */
+    msglev?: number,    /* message level for terminal output, default GLP_MSG_ERR */
+    presol?: boolean,   /* use presolver, default true */
+    cb?: {              /* a callback called at each 'each' iteration (only simplex) */
+        call(result: Result):Result,
+        each: number
+    }
+}
\ No newline at end of file
diff --git a/src/solver/jvail/Result.tsx b/src/solver/jvail/Result.tsx
new file mode 100644
index 0000000..1530fb2
--- /dev/null
+++ b/src/solver/jvail/Result.tsx
@@ -0,0 +1,10 @@
+export interface Result {
+    name: string;
+    time: number;
+    result: {
+        status: number;
+        z: number;
+        vars: {[key:string]: number};
+        dual?: { [key: string]: number }; /* simplex only */
+    };
+}
\ No newline at end of file
diff --git a/src/solver/jvail/Variable.tsx b/src/solver/jvail/Variable.tsx
new file mode 100644
index 0000000..664e3c7
--- /dev/null
+++ b/src/solver/jvail/Variable.tsx
@@ -0,0 +1,4 @@
+export interface Variable {
+    name: string;
+    coef: number
+}
\ No newline at end of file